Gas Check Boolits without Gas checks ???

[Fire_stick]

If your bullet is sized properly for your gun,
and if the pressure is sufficient to obturate the bullet per the bullet hardness.

Is there a need for a gas check? Even at elevated velocities?

From what I have been reading, I suspect the answer is, or could be no.

Although I also suspect powder burn rates may play a role in determining whether a GC is needed. Maybe it is simpler to use a GC and not worry with all the variables.

Please help me understand.

[camotruck]

Me too, help me understand, I thought that the limiting factor was the speed the pill was pushed down the tube and the friction generated on the bearing serfaces. Are we balancing beteen cooking the pill from the back and heat generated by friction?

Thinking.....................

The harder alloys let us get faster speeds and overcome friction and the GC lets us use more power / powder/heat to up the velocity.

Yes......No......

[docone31]

I had thought, mix some alloy, put on a gas check, and crank up that puppy.
Well, I learned better.
I believe, the gas check being harder than the boolitt, does prevent gas checking to an extent. Sizing is an issue here.
Useing copper as an example, it is harder than lead alloy. I am not sure how much as checks are thin. However, it does some scrapeing, and will fill the back of the casting as it travels down the bore. I am no expert, and I would love to find an alternative to swageing. I paper patch with great results in my .30s. No leading, good accuracy, fairly simple once the original point is achieved.
Specifically, how the gas check works is a mysery to me. I believe it does seal the bore, but with the loads I use for paper, the same load gas checked is a waste of time and lead.
I bet someone knows for sure here. I am interested in finding out also.

[Leftoverdj]

I don't know why GC's work. It's enough for me to know that they do. A while back, I honchoed a double run of .25 cal moulds. The two bullets were identical except that one was GC and the other PB. Accuracy with the PB bullets vanishes ar somewhere between 1200 and 1400 fps, depending on rifle and load. The GCed bullets still shoot well at 2400 fps.

[Slow Elk 45/70]

I would like to know the real answer also, I've been trying to find the answer for years, and the only thing I can see that makes much sense to me is that the GC protects the base of the CB from the propellant burn when fired at higher than 1700fps +- . I agree that it helps seal the bore.

I can't really prove this , just my theory from my humble experiences using PB & GC....
So if someone knows the real answer, please share

[Bret4207]

I don't know why GC's work. It's enough for me to know that they do. A while back, I honchoed a double run of .25 cal moulds. The two bullets were identical except that one was GC and the other PB. Accuracy with the PB bullets vanishes ar somewhere between 1200 and 1400 fps, depending on rifle and load. The GCed bullets still shoot well at 2400 fps.

And great design they are! We're all still in your debt for that run DJ!:drinks:

[Bret4207]

If your bullet is sized properly for your gun,
and if the pressure is sufficient to obturate the bullet per the bullet hardness.

Is there a need for a gas check? Even at elevated velocities?

From what I have been reading, I suspect the answer is, or could be no.

Although I also suspect powder burn rates may play a role in determining whether a GC is needed. Maybe it is simpler to use a GC and not worry with all the variables.

Please help me understand.

I'll give you my understanding, it'll be in simple terms and is only my opinion.

Yes, there is a need for gas checks once you pass a certain point. That point varies from load to load and gun to gun, even ambient temp can affect it so your summer load might need it and your winter load not.

Obturation is an iffy thing, sometimes it happens and good results follow, other times it happens and bad things follow. Same for when there is no obturation. In a perfect world the would be no obturation- the boolit wild precisely fit the throat area and the powder would gently start the boolit down the barrel without distortion. That's why Harry Pope and Zischang and Schoyen and all the other old time lead boolit shooters used a false muzzle and muzzle loaded their guns. Most of us won't do that. We prefer fixed ammunition, so we try and hit a happy medium.

Different powders, primers, case shapes, throat shapes, seating depth, alloy, boolit design and size , rifling type and condition, even ambient air pressure can cause variations in the burn rate and pressure curve of a given load. SOME plain based boolits in SOME guns will be extremely forgiving of all those variables and will tend to shoot good up to somewhere around 2000 fps. At least those are the claims that have been made. You will occasionally hear of someone who gets 22-2300 fps for 5 shots or so. If this is true, these guys shouldn't even bother picking up a lottery ticket, they've used all their luck up!

In an average rifle those variables will stack up in a seemingly random order and usually limit your plain base shooting to under 1600 in general no matter how good a fit you have. That 1600 fps can be 1200 in some guns, 1700-1800 in others, larger calibers tend to be more forgiving. If, IF you go to a slower powder, a harder alloy, maybe a little larger boolit and a super lube and a filler you can up the speed. Maybe. It might work one day and not the next.

In handguns the PB generally works up to 11-1300 fps given good fit, etc as with rifles. Cartridges like the 45ACP can be used at factory velocity with PB with little problem, same for the 32 ACP and 380 ACP. Low pressure! Take a 9mm and you're good to a certain point and then it's lead city. Same for the 38, 357, 40S+W, 44 Special and Mag and of course the any of the other hotter rounds. Pressure seems to be the bad guy here and to me at least, it seems to work a little differently in handguns than in rifles.

A gas check just makes achieving higher velocity at a higher pressure easier. IMO boolit bases do not, and have never "melted". There isn't time enough , even under the pressures involved, for the heat transfer to take place. IMO what happens at the base is that the pressure pushes the lead around and like a rock thrown in mud there is some splashing. The rougher and weaker the base and alloy the more splash. Lead alloy is ductile and if you've ever hit an ingot with a hammer you can see that you don't get a smooth surface when you've hit it. I believe this takes place and the "splashed" particles are minute, maybe microscopic in size even.

The same general theory goes for the sides of the boolit once it's moving- only now you have hot gases trying to rush past the boolit through any gap between boolit and barrel. The alloy doesn't "melt", the gases abrade the boolit surface (and of course a rough barrel can help this happen too) and the particles of alloy are blown onto the barrel surface and pressed on by pressure. At least that's my understanding. There can also be the instance of lube failure where the alloy is actually rubbed into the barrel surface. I call it lube failure, but it may actually be something else.

So what does the GC do?

1- Provides a scraping action to the barrel. The edge of the check theoretically scrapes lead from the boolit ahead of it away from the barrel.

2- Provides a seal of sorts in a properly sized gas check/barrel interface. An undersized gas check is a waste of money. What the tolerance is depends on the gun and load, but as a general rule I want my checks at least bore size and preferably closer to groove size. If the check is under bore size it's effect is drastically reduced, may not work at all and is wasted money.

3- Provides a much stronger base to the boolit and one that remains square throughout the boolits journey up the barrel. This I've seen- seat a check crooked and shoot several groups with crooked checks and square checks. It don't take a genius to see the difference.

4- Makes achieving higher velocities at higher pressures EASIER. That doesn't mean the sky is the limit. There comes a point where the alloy can't take the pressure/velocity/rifling anymore and you get leading and wild shooting. But the GC makes it easier to go faster using pressure to boost speed.

That's my understanding at this point. 10 years ago I had a different opinion, 20 years ago it was different than that! I used to think hard, hard, hard!!! I thought that would solve all the problems. Not so. A GC won't solve it all either, but it does reduce the variables in most cases.

[MT Gianni]

Veral claims a check will aid the base in strength and prevent it from stripping out in the twist. I would add that to Brets excellent points.

[SlamFire1]

In a 30-06, I tried Lyman 311299 and 311284, lyman #2 alloy, with IMR 4895 without gas checks. Measured velocities were between 1700 and 1800 fps.

Without gas checks I got six foot by six foot groups.

With gas checks, the things shot much better.

I am sticking with gas checks.

[Papa smurf]

In relation to just accuracy with or without a gas check , I think the gas check gives the boolit a more uniform base . A good crown will give better accuracy than a poor one , therfore a good base will give better accuracy and the gas check being stronger as well as uniform will allow this. Any and all replies please
Good shooting---------Papa Smurf

[Cap'n Morgan]

The two bullets were identical except that one was GC and the other PB. Accuracy with the PB bullets vanishes ar somewhere between 1200 and 1400 fps, depending on rifle and load. The GCed bullets still shoot well at 2400 fps.

Noticed the exact same thing with a 2-in-1 mold (PB + GC) I made for my 375 H&H. I cooked up a load in the 1600 fps range and shot a nice group with the checked boolits - the plain based, however, couldn't stay within an A4 sheet at 50 yards.

This was with a 325 grains bullet. My gut-feeling tells me a heavy bullet amplify the problem, but I don't know for sure.

[felix]

It's for sure, Cap'n. It is much harder to rotate a heavier projectile. ... felix

[Fire_stick]

Thanks guys for all of the replies. This is just what I needed.

Bret4207 - thanks for your thorough post. This helps me begin to tie everything together a little better.

[Bret4207]

I'm a little amazed no one told me I was completely wrong about all of it!

[armyrat1970]

I'm a little amazed no one told me I was completely wrong about all of it!

Okay, you're wrong.:-D Naw. I think you gave a pretty good indepth explanation. Thanks. It's something we all wonder about I'm sure. I would like to add one thing to Bret's though. Many feel that the harder the bullet, the less leading. This is not true. Even with handgun cast bullets you can get leading if you drive your bullets to hard. A softer bullet at a lower velocity will many times cause less leading than a harder bullet at a higher velocity. The bullet will skim over the lands and give greater leading issues. You have to find the right mix of hardness, pressure and velocity. Velocity is not always the key factor. It takes time and experimentation. But it's all part of the fun of what we do as a hobby or an art. We should worry more about accuracy from our cast boolits, not velocity from the weapon. The one that you hit and drop won't know if your bullet was traveling a couple of hundred fps faster or slower anyway. Neither will the one you miss.

[Slow Elk 45/70]

Thanks Bret for your insight, and others, this has always been a point to ponder for me, so now I can chew on all this for a while, [smilie=1:I am leaning toward your pressure theory along with most of the other points, there is no simple answer.....:roll: It seems to be a compilation of several factors affecting the boolit

I will keep using the GC on mine over 1600+ , :Fire:

[Bret4207]

Thanks Bret for your insight, and others, this has always been a point to ponder for me, so now I can chew on all this for a while, [smilie=1:I am leaning toward your pressure theory along with most of the other points, there is no simple answer.....:roll: It seems to be a compilation of several factors affecting the boolit

I will keep using the GC on mine over 1600+ , :Fire:

Ah Grasshopper, the light at the end of the tunnel is no longer the oncoming train!!!:drinks:

[grouch]

Maybe check with the guys who shoot the single shot matches at the CBA - they certainly get respectable results. I suspect we've lost a good deal of that technology.
Grouch

[Larry Gibson]

Maybe check with the guys who shoot the single shot matches at the CBA - they certainly get respectable results. I suspect we've lost a good deal of that technology.
Grouch

Grouch

I don't think we've lost any of that "technology". I doubt any of the single shot match shooters shoot over 1600 fps and doubt many of them shoot over 1400 fps. At least the shooters in the single shot matches here don't.

Larry Gibson

[GLynn41]

If i ever get around to publishing the pics. I have shot my MM brass mold 255.41 many times with out the cg and it does just fine out of a handgun no clue yet as to the rifle-- but mine at least will shoot very well with or with out in a 5.5" Rhawk .41 AA#9 15.5 gr bullet weight is about 248+- so yes they can or so it seems

[crabo]

I think that it is easier to find a load that shoots well with a good gas checked boolit than it is with a plain based boolit. The plain based boolits have the potential to shoot very well. It sometimes takes a lot of load developement to find a load that shoots well. I can sometimes find a good load quicker with a GC'd boolit than a plain based boolit. Of course, of my last 3 Mountain Molds I had made, one was a gas checked, and 2 were plain based.

I think as you push the velocity, the gas check becomes more important. However a lot of boolits, especially heavy for the caliber, seem to me, to take more velocity to shoot well.

I think the gas check helps compensate for "everything that is not quite perfect".

Another very important factor, which I don't think any one addressed is "What are your accuracy standards?" With a revolver, some people are happy with 2 1/2" groups at 25 yards, some want the same size group at 50 yards, and some want the same size group at 100 yards. What is good enough for you?

[303Guy]

3- Provides a much stronger base to the boolit and one that remains square throughout the boolits journey up the barrel. This I've seen- seat a check crooked and shoot several groups with crooked checks and square checks. It don't take a genius to see the difference.
I think Bret4207 hit the nail on the head! (I only have enough knowledge and experience to 'think' at this stage!) I have had hard bullets flame cutting and softer ones shooting good (PB) in a revolver). I have had PB bullets shooting sooo good in a carbine (Rossi 357) - soft lead. Recently I have had WW with gas-check shooting rather well. I have also had flame cutting with brass bullets. Last trick was a bullet with it's gas check missing. This is where things get interesting! Check this out!
http://i388.photobucket.com/albums/oo327/303Guy/MVC-568F.jpg
Notice the deformation of the base? Close examination shows zero flame cutting and the bore showed zero leading. But a rough bore produces flame cutting with a gas check and a good bore none with a gas check and some without. This particular bullet was fired through a bore that previously flame cut (before a little bit of aggressive fire-lapping!)
Here you can see the difference. (These were reject bullets used for testing as can be seen).
http://i388.photobucket.com/albums/oo327/303Guy/MVC-311F_edited.jpg
This shows how the bullet was lubed.
http://i388.photobucket.com/albums/oo327/303Guy/MVC-338F_edited.jpg
This shows how a gas check did not help in a rough bore.
http://i388.photobucket.com/albums/oo327/303Guy/MVC-314F_edited.jpg
Compare this one to the first pic - same bore, before fire-lapping.

So, what I am suggesting is that the gas check helps support the bullet base, keeping it square under pressures that actually obturate the bullet, giving the bullet a proppe seal which prevents flame cutting. My lube system probably helps as the bullet has no choice but to ride a lube film. These bullets are also over groove size. In fact, they only just fit into the throat.

Preliminary test results are encouraging. All seven test shots were close together like this. There was no leading.
http://i388.photobucket.com/albums/oo327/303Guy/MVC-457F_edited.jpg

The bullet.
http://i388.photobucket.com/albums/oo327/303Guy/MVC-503F.jpg

I should stress that this is still early days!

[243winxb]

Lee wants the pressure below where Obturation would happen. http://www.realguns.com/archives/118.htm Compare the pressure listed here for Obturation to take place.http://en.wikipedia.org/wiki/Obturate If a cast lead alloy bullet Obturates, it will deform and break down, leading the barrel. The structure of the bullet will be changed when jumping for the cylinder to the forcing cone. Not so much change will take place in a auto fixed chamber firearm. Bullet's BHN x 1422 = Pounds per square inch.
Quote:
According to the chart, a very popular #2 alloy carries a 16 BHN, has a strength indictor of 22,703 PSI and should be limited to 20,000 PSI as maximum pressure. Wheel weight alloy with a BHN of 9 carries a strength of 12,748 PSI and a MAX pressure rating of 11,473 PSI." You will need a gas check if the pressure is to high for the lead alloy your using. If the bullet is designed for a gas check, use one.

[243winxb]

A bullet jacket/GC is 90 % copper and 10 % zinc. The chat lists copper alone to withstand 56,900 PSI @ a BHN of 40 at when Obturation takes place. The copper alloy GC even go to a higher pressure. But the speed then becomes a factor with friction on the barrel walls. So 2200 fps is max velocity.

[Bret4207]

243, as I said, obturation is an iffy thing. For decades induced obturation was used to make a boolit fit the barrel. That's the reason for all those HB boolits and why BP gave so much better accuracy for the first quarter or half of the 20th century. Given proper fit the last thing I want is obturation, as I said in my earlier post. However, there are still situations where a bit of obturation will increase the consistent accuracy and performance of "pick up" loads.

I would have to disagree with with this line in your post- "If a cast lead alloy bullet Obturates, it will deform and break down, leading the barrel." There have been many hundreds of thousands of boolits shot accurately and without leading even though the boolit obturates. The statement you made could well be changed to, " A boolit which obturates in the throat will sometimes be reformed to better meet the needs of the barrel through better fit."

There are few hard and fast rules in this games as we all have different expectations and requirements. My opinion is that fit is king above all else in this game, others will say it's alloy or boolit design or Bhn. I can only agree with Lee's statements if the boolit is properly sized to the gun in the first place.

[44man]

Veral claims a check will aid the base in strength and prevent it from stripping out in the twist. I would add that to Brets excellent points.
This is indeed the most important thing a check does. I am surprised Bret missed it. Bret was not wrong with all of his assessments, he just forgot this one! :Fire:
Even with PB boolits I see wide land and groove marks but as long as the marks on the base are back to land and groove size all is well and they are accurate. The gas check will help halt skidding and let the boolit take the rifling at the most important point when velocity is raised.
Plain and simple--ALL bullets skid, even jacketed ones, when forced to turn.
Once you raise velocity too high with a GC boolit and it fails to maintain a seal and grip, accuracy will also fail.
Slower powders can ease a boolit into the turn, increase accuracy and reduce leading. Anytime a boolit skids and widens the marks at the base, gas can abrade the sides of the boolit.
Notice that very small cases with very fast powders lead bores much more then anything else.
Never believe that a GC will prevent leading if shot beyond the grip point, THEY WILL ALLOW A BOOLIT TO LEAD A BORE! [smilie=1:[smilie=1:
Alloy hardness will aid grip closer to the front and allow higher velocity.
The gas check was designed to let soft boolits take the rifling but we now exceed by a wide margin the slow speeds shot long ago. I do not believe in obturation or soft boolits in any form for revolvers or modern rifles.
Soft boolits are right for BP, muzzle loaders, etc. Obturation still does not work for them either, make the boolit or ball fit first.

[Bret4207]

Well, here's my problem with that theory. I'm not sold entirely on it because it doesn't address the front of the boolit. Take a nice long boolit, a 160 gr 6.5 Cruise Missile maybe. If I look at a fired example and don't see skid marks does that mean the GC prevented it or does it mean the rest of the boolit fit the throat and barrel and performed as it's supposed to. If I do see skid marks and they stop at the GC then is it because of the GC or because the pressure dropped about that time and skidding stopped? If it stops in the middle, before the GC could be in the rifling, then how does it grip the rifling to stop the skid? I agree that once the GC is in the rifling it should help grip both the boolit base and rifling. Until I'm inside a barrel watching it happen I doubt anyone will know for sure.

On another, related matter- if I use a correctly sized boolit of 11 Bhn and shoot 1" groups at 1900 FPS and also shoot a correctly sized boolit of 24 Bhn and shoot that same 1" group...what gain did I get by using a harder , more expensive alloy? Either way I fitted the boolit to the gun and it shoots very well for me. The Bhn has little to do with successful cast boolit shooting or hunting IMO. You feel more comfortable using hard alloys, that's fine. IME I save the harder alloys for specialized uses and am quite happy with what I get from my standard "soft" alloys.

[Slow Elk 45/70]

Bret4207, I have read and re-read all of these post and a lot more on this subject.

I am glad no one said you were wrong, because it is hard to prove these "THEORIES" if there was one single answer, I'm sure someone would have passed it on or we would discover it, with as many people as we have searching for this answer. I also surcribe to the theories that the GC stops the boolit from "skidding"

I used to think more speed ,harder also with cooking the base of the boolit, but not now,
I am going to go with the a little of this and that and the GC makes higher velocity without leading , EASIER, all the other variables make the rest of the equation. IMHO[smilie=1:
I have used the GC on my rifle loads 1700fps and over for a long time, and it works for me. I have never tried to go past about 2100fps, just because I have no need to shoot a CB faster. All of my pistol shooting is +-1300 and under, mostly under.

Thanks to all for all of the theories and opinions.:drinks:

[Fire_stick]

Wow, this is a good read everyone! Thanks for all the info.

I had no idea I would open a can of worms like this. I am still just figuring all of this out, and I will be back here studying. I hope I get as smart about this stuff as you guys.

I like to tinker and experiment, but I am short on time and cheap, too. I sure don't want to be cleaning lead out of my barrels:groner: if I can avoid it. And if I can avoid an extra cost (drop the gc) I want to do that. So far I have avoided leading. Maybe it's because I followed some of the same "rules of thumb" found in this thread. Maybe I was lucky. Time and trial will tell. I am to the point now where I am going to start pushing the envelope on PB bullets (I almost wrote boolits).

What I have gathered so far - Have a goal, know your firearm (it's variables and limits), create a bullet and a load that works in your gun to reach the goal. If need be, adjust and try again until you get it where you want it. Keep good notes.

[Bret4207]

Slow Elk- I think many of us here are on the same boat. There comes a time in this hobby where you have the basics down, you've played with this and that and you've figured out what a few guns like, you've shot successfully at 2200+ fps, played around with fillers and heat treating and more SN/SB, HPing, bumping, teflon, graphite, fire lapping......the list seems endless. But a lot of us get to the point when we realize the are very few hard and fast rules in this game, no "do this and it ALWAYS fixes that!" type answers. Much of what we do is based on theory and those theories depend on our observation and conclusions. Sometimes we run into a gun that defies all logic and just won't shoot with anything. Other times we get one that swallows any old boolit and plunks them into the black. Why? Who knows. That's part of the reason I'm still mulling over the GC question. I know it stops skidding in some cases, but there are other things that help do that too. So I'll say that once the GC is in the barrel it helps prevent skidding. And then I'll continue to mull it over and come up with a more complete theory.

IMO we have a set of basic suggestions that seem to work in most cases. You hit one on the head- the GC makes it EASIER to achieve good, consistent grouping and lead free shooting at higher velocities. It helps, but there are other things that go with it to increase your odds like fit (above all else), pressure curve, alloy strength, boolit design and others.

I don't mean to sound smug or anything, but when you get to the point you realize there is no "magic boolit" I think that's when the real learning starts.

[Bret4207]

Wow, this is a good read everyone! Thanks for all the info.

I had no idea I would open a can of worms like this. I am still just figuring all of this out, and I will be back here studying. I hope I get as smart about this stuff as you guys.

I like to tinker and experiment, but I am short on time and cheap, too. I sure don't want to be cleaning lead out of my barrels:groner: if I can avoid it. And if I can avoid an extra cost (drop the gc) I want to do that. So far I have avoided leading. Maybe it's because I followed some of the same "rules of thumb" found in this thread. Maybe I was lucky. Time and trial will tell. I am to the point now where I am going to start pushing the envelope on PB bullets (I almost wrote boolits).

What I have gathered so far - Have a goal, know your firearm (it's variables and limits), create a bullet and a load that works in your gun to reach the goal. If need be, adjust and try again until you get it where you want it. Keep good notes.

I see great things for you in your cast boolit future!

[Hanshi]

FWIW, I've used GC boolits without the GC with very good success as long as I kept velocities down. If the (boolit) alloy is too hard, and it usually is in commercial cast boolits, they won't obturate and gas blow-by will solder lead lumps inside the forcing cone and first inch or so of the barrel. This is in revolvers mostly and is not so much of a problem in autos. Plain base boolits are much better at the higher velocities, of course, but I don't hesitate to use GC designs without the GC.

With the GC attached I've found I can easily surpass jacketed velocities with minimal 'flash" leading and NO buildup. On examination of fired GC boolits I usually find the GC still on and very well obturated, this, even with cast GC rifle boolits at 1600 -1899fps. :drinks:

[Slow Elk 45/70]

Bret4207 , I agree, and yes the GC has to enter the barrel to help stop skidding and all else. I'm with you. Like you say , there are way to many variables for any one thing to be a cure.[smilie=1: One needs to develop his plan for his own needs and guns, they are all different. We have all the basics and know what works, most of the time, the rest is trial and error.

If there is a "Magic Fix" out there, please send it along:drinks:

[Hanshi]

In my experience plain based boolits do well in rifles as long as velocities are kept in check. Never had a problem with GC styles at deer killing velocities, either. Revolvers can be quite picky as to what they like since there are so many variables to consider. I know of no overriding rule that would apply, either.

[Old Ironsights]

OK, let's take this one step further.

Assuming a standard mould (358156) being used for general plinking, running up to maybe 1500 out of a carbine.

Would it make sense to, assuming the same 3/1 alloy and if you have 2 moulds, have one mold releived of the GC shank to make it a PB, or will it really matter all that much shooting with the shanks bare?

[uncowboy]

Gas Ck and accuracy. The gas ck is not so much sealing the bore better what it is doing is handling the ROTATIONAL FORCE of the bullet better than lead. This along with NOT alowing the rear of the bullet to deform increases accuracy. Heavy pressure on the back of a lead bullet causes it to spin out of the lands and groves giving you the 2 foot groops we have all had. This also is why we have leading. When we make lead HARDER we also make it more Brittal This gives the same poor performance for the same reason. Think rotational force when thinking gas cks. J.Michael

[LqChrome]

I'm with OI. What happens when you shoot GC Boolits without GCs at low velocities?

[runfiverun]

i'd rather have the plain base boolit over the checkless one if i am gonna push it.
i think the role of a gas check is just that, a barrier between the gas and the boolit.
it helps stabilize the boolit from further stripping remember in the beginning the boolit is moving forward then it is being turned.
the g/c helps with the engagement stability.
i think without it you could conceivably push the boolit straight down the bbl.
this is how i think about leading in parts of the bbl, pressure letting off further down the bbl can contribute to leading as much [or more than] lube failure by allowing the unchecked boolit to relax. the check don't relax. you might also see lube/powder fouling in parts of the bbl from this, even though there is no leading. with a g/c

[windrider919]

For years I have salvaged range lead to recycle into more bullets. And being the curious cat that I am I collected many examples of different style and caliber of bullets. If you examine just about any bullet, jacketed or not you will see that for a fraction of an inch the rifling engraved on the bullet is wider. It is obvious that the bullet, going straight forward starts engaging the rifling yet inertia / momentum keeps it from instantly starting to turn. then the twist of the rifling overpowers, so to speak, the inertia and the bullet starts to turn. On bullet after bullet this happens in .050 to .075 of an inch. By then the rifling twist and bullet are in sync. The width of engraving into the surface of the bullet is parallel down the length of the bullet. If the bullet were to "skid' then the groove engraved into the bullets side would NOT be parallel but would be non-parallel. Wider at the nose and tapering to the base. And it would be wider than the rifle bores lands. So, real world: examining thousands of bullets fired from hundreds of rifles in numerous calibers I never found one that had skidded all the way to the base. I did find some that had skidded 1/3 of the contact length but never more than that. So I hate to disagree but the theory that the gas check, at the base of the bullet, stops the skidding of the bullet is shown to be mistaken. However, I should say that I have seen pure lead swaged bullets that were under size [.301 instead of .309], and loaded to max pressure / velocity strip out completely in a 30-06 firing a 165 grain gas checked bullet. Leaving a long curl of lead on the edge of each lands leading edge. The key here is that the bullet was UNDERSIZE and could not really get full engagement of the rifling, and lots of gas could blast past the bullet.

Match shooters worried that the distortion of their bullets as they entered the rifling have tried progressive twist barrels to 'slowly, gentilly ' start the bullets spin. And since the proof is in what we shoot, it must not work very well because we all still shoot consistent twist barrels. If it made a difference we would make the manufactures give us what we want and pay the extra cost.

My belief, because that is what we are all putting forth here is our beliefs, is that the gas check acts as both a seal and a scraper. Going down the barrel the high pressure gas is trying to push past the bullet. If that bullet is groove size or less then the gas has a better chance of pushing past, gas cutting the side of the bullet and the vaporized lead depositing on the 'cold' bore. Following shots bullets sides then gall and tear off material from the bullet. The same mechanism of galling happens with many metals such as stainless bolts in a stainless piece. So the leading gets worse and worse. By the way, high speed photography of jacketed bullets has shown that there is frequently a puff of propellant gas exiting the bore ahead of the bullet along with the displaced air in the bore that the bullet pushes ahead of it. That means that there is blow-by around the jacketed bullet but it is so small an amount and it does no harm (like leading does) that it is ignored. If a lead bullet is undersize or distorts for some reason (cocked in the chamber?) or is too hard to obturate than the high pressure gas is given a path to slip past the bullet and damage it. The gas check, assuming a proper size to the bore {traditionally .001 over groove} then swages down to fit the barrel, preventing blow-by. And, if there is lead or fowling present it acts as a scraper to push it ahead and ..well, scrape the barrel clean(er).

Today I shoot Paper Patch because I will not pay the price for trick expanding J-bullets. I went to cast bullets but objected to the cost of GC too. Looking for a way around that and still desiring to shoot higher velocities than 1400 I found I can shoot up to 2200 with a PPed lead bullet. That also proved to me that no lead was vaporizing off the base of lead bullets because the paper exposed on the base does not burn. If the paper does not burn up than the lead d**** well is not either! But what about gas cutting you might ask in rebutal? The answer is that it is an apple and orange question. They are different because the gas cutting effect is not a function of heat, but a function of gas velocity.

I have and do shoot regular grease grooved, gas check shanked bullets but withOUT GC that I PPed and shot at various velocities between 1600 to 2000 FPS. No leading and pretty fair accuracy too. My proof is in the pudding so to speak, I have proven to myself that high(er) velocity cast bullets do not have to have a GC to shoot well.

[windrider919]

I should to my post above

PS: I stated that blow-by around a jacketed bullet does no damage but then I remembered that in 1987 I bought a Springfield Arms M1A1 which some of you might know as a simi-auto/ civilian M14. Paid for the match barrel and everything since I was shooting NRA High Power Rifle at the time. Well, about a year later I ran across a 1000 rounds of Chinese 7.62/.308 ammo. I was told it was not reloadable (different primer type) but it was REAL cheap!!! Now I had shot that rifle in 16 matches and about 40 practice sessions and I had an excellent reload. The barrel still had a glass smooth finish. I took my cheap ammo to the range and started to practice. I was disappointed because where I usually shot 1 1/2" or less groups at 100 yards this ammo was giving me 20" to 24"! I had only shot 20 rounds and when I picked up the brass I saw that there was powder soot around the primers. And when I looked at my bolt face I found it all carboned up. Yes, I should have thrown that cheep ammo away but it had cost something, right? So the next week some friends and I went out to west Texas and had a day of rapid fire fun. Imagine my horror that night when I found my bolt face had a circle etched in it the size of a LR primer from gas cutting. And it turned into a nightmare when I looked down the bore at the pitted and ruined bore. 600 rounds had literally, totally destroyed the barrel. Later I pulled some bullets and found they miked .3065. And yes, I did finally throw the rest of that Chinese ammunition away. Like the old saying, "You get what you pay for." The undersize bullets had let high pressure gas past and cut and etched the barrel steel. Same way we use high pressure water to cut steel in the shipyards nowdays. A perfect example how gas cutting can ruin your day. I tested the remaining accuracy with my 1" handload and got 1 foot groups at 100yds. I had to replace the barrel which cost about half of what the original rifle cost.

[David2011]

Really interesting thread, guys! I just finished a rifle I built in gunsmithing school, chambered in 6.5x55 Swede. I have a large quantity of 120 gr soft point jacketed commercial bullets but still want to try some boolits in it. Now I'm confused. My standard handgun alloy for years has been 20 lb. wheelweight to 1/2 lb monotype. It works for anything from .38 wadcutters with 2.3 of Bullseye to .45ACP at all velocities to .40 S&W making IPSC major. I've hot tens of thousands of these boolits, no GC, since 1982.

I have thought for years that straight lino with a gas check was the way to go with rifle boolits. This info makes me think that anything from straight mag wheelweight Pb to pure Monotype might be the right alloy. I assume I would need a GC at 6.5mm, thinking that around 1700-1800 fps would be a good target velocity. I have never cast or shot a cast rifle boolit. Actually, I haven't owned an appropriate rifle until I built the on in 6.5x55. Any suggestions?

A friend gave me a long Mauser action already modified to large magnum, bolt face opened to H&H Mag size along with a .375 barrel, .375 H&H reamer and go gauge. I thougt it might be fun to shoot at around 1700 fps with cast boolits. Anyone have any experience there? With or without GC?

David2011

[willyboy]

Sounds more like corrosive primer caused damage than gas cutting to me...

[leftiye]

David, FWIW the Swede is a topic of much interest here - in the vein of it being a hard caliber to load cast for if heavy boolits are used due to the loooong boolits and fast twist. But read up on it, it is a fairly popular old military caliber and can be loaded, just you've gotta work at it. As for the .375 H&H, it may be an overlooked caliber on this board (here), but maybe THE BEST CAST CALIBER GOING! IMHO. An excellent compromise in boolit diameter and boolit weight for good velocity (due to large case), moderate recoil, and good killing power. I luv the .35 Whelen, but the edge is undisputably for the .375. Good wabbit medicine too! (unbelieveable - hits like a high velocity .22).

[badgeredd]

I luv the .35 Whelen, but the edge is undisputably for the .375.

leftiye,

Please explain this statement. I love my 35 Whelen and my 358 Norma Mag. How is the 375 so much better?

Edd

[6.5 mike]

Correct me if I'm wrong, but doesn't using a g/ced mold without a g/c set us up by allowing a path for gas to work on the smaller dia base unlike a true p/b mold? Iv'e not tried this execpt with pistol boolits, but, with a rifle boolit at a higher vel, it seems that
would happen.
I haven't been doing this near as long as ya'll , but I think all have valid points. Is it a combination of factors that cause leading, or only one incorrect factor? Maybe someone one day will figure it out, until then we'll plug along trial & error. just my .02

[leftiye]

Badger, Mainly bigger case capacity. Allows use of slower powders for lower pressure higher velocity cast loads without early high pressure spike (you hafta find the right powder still).

Just as importantly larger bore. Larger bore equals better killing power, especially if you don't use expanding boolits. Heavier boolits in the 300 to 350 grain range also.

[XWrench3]

i am certainly no expert, in fact, this post will certainly show how little i really understand about these. but i always thought that gas checks should be doubled up. like welded together, back to back. one side crimped on like they do, the other side facing backwards so they would act like a bevel base bullet. sealing all of the gas pressure behind the bullet. kind of like this.... ><bullet

[BOOM BOOM]

HI,
I would bet that the 375 could be loaded to 2,400-2,500 w/ cast w/ good acc.
seems to me the bigger dia. slugs are also more forgiving of my mistakes.[smilie=s:

[a.squibload]

i am certainly no expert, in fact, this post will certainly show how little i really understand about these. but i always thought that gas checks should be doubled up. like welded together, back to back. one side crimped on like they do, the other side facing backwards so they would act like a bevel base bullet. sealing all of the gas pressure behind the bullet. kind of like this.... ><bullet

Dang, that sounds good. Like the leather gasket/skirt in the pump for a
Coleman stove, only the other way around. I'm thinking short tube to align
the checks as you spot-weld them together. Do a few then test in the sizer
to see if it squishes the open GC. Loading into a case shouldn't hurt 'em.
First check is the scraper, second is the seal. Would it work better? Who
cares? We'll sell a million of 'em! Have your people call my people...

[Fire_stick]

...........

Today I shoot Paper Patch because I will not pay the price for trick expanding J-bullets. I went to cast bullets but objected to the cost of GC too. Looking for a way around that and still desiring to shoot higher velocities than 1400 I found I can shoot up to 2200 with a PPed lead bullet. That also proved to me that no lead was vaporizing off the base of lead bullets because the paper exposed on the base does not burn. If the paper does not burn up than the lead d**** well is not either! But what about gas cutting you might ask in rebutal? The answer is that it is an apple and orange question. They are different because the gas cutting effect is not a function of heat, but a function of gas velocity.

I have and do shoot regular grease grooved, gas check shanked bullets but withOUT GC that I PPed and shot at various velocities between 1600 to 2000 FPS. No leading and pretty fair accuracy too. My proof is in the pudding so to speak, I have proven to myself that high(er) velocity cast bullets do not have to have a GC to shoot well.

windrider,

I have tried paper patching regular gc 357 and 44 cal pb bullets with excellent results so far, up to 1950 fps.

I did finally spend some money on gc's so I can run some comparison tests with proven pp loads I have developed for my guns.

Thanks again to all for the good content in this thread.

[Oyeboten]

So...what ever happened to progressive Rifleing?


I heard the Colt Dragoons had it...various Rifles of course did back when.


What about now?


All these 'skidding' woes could become a thing of the ( recent) past!

[Artful]

Oyeboten see these links
http://www.riflebarrels.com/articles/barrel_making/twist_machine.htm
http://www.riflebarrels.com/articles/barrel_making/details_of_accuracy.htm

[hunter2]

Bartlein barrels are making progressive twist. Not long ago Toby won a championship with one in 22 cal.. There is a fellow in Canada who has done a lot of work in this design. Do they work? Yes. Are they better than fixed twist? Yes No Sometimes!!!! But are they any good for cb's? If they gain even an inch over the length of the barrel, my gut says this can't be good. But! I would happily try out a couple if they are donated....Getting back - Veral says that if his lube is used ( and I shoot under 1050 ) there will be little to no leading and the next bullet will clean it out, and barrel will never need cleaned..... Going to give it a try....Would too hard be the reason the 80's marlin 444 will not shoot comercial bullets worth a darn?

[Papa Jack]

Sorry, I didn't read all the posts here....

I just loaded 150 rounds of Lee 180 grn GC ( without the GC) lubed with Tamarack 50/50, loaded with 12 grns of Red Dot and a little TP wad, cast of home made Lyman #2, sized .309"..
So far I have only fired 50 rounds, all at the same sitting (slow fire) and I have NO LEADING at all.
Using a O3-A3 Rem. with 2 groove barrel, issue sights.
Accuracy was "Pie Plate" at a measured 100 yards, not really trying as I was fire Forming the brass ( I set the shoulders back when I sized em years ago )..... "Papa Jack"

[BackWoods Billy]

1st off,let me say this is a great site.Came over here for a GB on a mold.Now it's hard to stay away. I'm pretty sure that this goes along with this thread.If some one could tell me what may cause this on this Barns .429 XPB 225gr. Looks to me as if it didn't grab the rifling right. This was put through a SBH 7.5" barrel with 21grs. H110.
http://img600.imageshack.us/img600/7237/barnsxtp.jpg (http://img600.imageshack.us/i/barnsxtp.jpg/)

Uploaded with ImageShack.us (http://imageshack.us)

[SwampYankee]

This was a excellent read. I've only been here a short time, but I'm sure impressed with the knowledge shared so freely. I'm on a lot of forms for different hobbies, but this one has taken up the last week. Great thread for sure.

SwampYankee

[hunter2]

Have a 357 Handi Rifle that does the same thing. Long throat and shallow rifeling. My SWAG is- the bullet does not always enter the bore straight. Most are heavier on one side. Have slugged the bore and they are shallow but straight. Almost as the slug enters at a few degrees of angle. Could the bore not be fully concentric with the chamber?

[windrider919]

Back when I trained as a gunsmith under Ron Freshour in the 80's we ran across multiple rifles including factory Rems, Wins, etc where the chamber was not concentric with the bore. This was especially disturbing when the rifle had come from some famous high priced gunsmith after re-barreling and would not shoot so was brought to us to check out. If the person running the chamber operation is not paying attention is is easy for the reamer to cut more on one side than the other. Once this starts the reamer will NOT re-center itself. The gun will shoot but it will never be as accurate as it could have been if the chamber was in line with the barrel bore. The only solution is to cut off the bad chamber and start again. We did try the bore out the chamber and press in an insert which was re-chambered on some valuable rifles for which no replacement barrel was wanted or available. It works with 'standard hunting accuracy' but will never give that 'tack driving

Also, some reamers leave an oversize throat that let the bullet slightly cock as it moves forward into the rifling at firing. The bullet then is swedged lopsided which destroys its potential accuracy. Its Center of Gravity will not be the same as its Center of Rotation which causes larger groups or even a 'flyer'. One of the joys of Paper Patching is that you can have a bullet that is a few thousands under barrel size and use the PP to fill up the oversize throat and keep the bullet centered and aligned. When it fires, the paper is compressible and does not generate the extra dangerous high pressure a 'hard' bullet like an oversize jacketed or regular {similarly oversize} grease groove cast bullet would. Tailoring the bullet to fit the chamber can lead to some amazing accuracy from what were considered 'poor shooters'.

[Scramjet]

Excellent question:
I've been dealing with this preparing first time load development for two new Ruger revolvers this winter.

One being a 44spcl load from suggested starting loads to 7.5gr Unique under a 240gr cast boolit that is a gas check design not gas checking them (what a pain cleaning lube from gas check recess once sized and lubed prior to loading).

The other a 44 mag loading Accurate#9
from suggested starting load to under max using a 250gr non-gas checked boolit design both traveling under 2000fps.

Plan is to paper punch until comfortable with both firearms, from there start into max loads gas checking.

If wrong helpful suggestions welcomed.

Thanks,
Tom

[windrider919]

Scramjet, here is a suggestion for shooting cast bullets with gas check shank in revolvers.

Get or fabricate a punch for .010 (ten thousands) more that the bore. Then go to the Dollar store and buy one of the cheap dough rolling sheets {for a buck!}. They are made of Polyethylene ( PE ) about .020 to .035 thick and are 24" X 24". You can make a few thousand wads from one. So when you have the powder in the case, use a dowel to push the wad into the case just below the mouth. then load the gas checkless bullets to dept and crimp if thats what it needs. The wad should be against the bullet base (may be slightly bowed away in the center due to oversize wad dia. I found in my Ruger Speed-Sixes I got better groups without gas checks but WITH the PE wads. The same in my Super Blackhawk.

It's a cheap experiment to try and cheaper than copper gas checks to shoot!

[badbob454]

I'll give you my understanding, it'll be in simple terms and is only my opinion.

Yes, there is a need for gas checks once you pass a certain point. That point varies from load to load and gun to gun, even ambient temp can affect it so your summer load might need it and your winter load not.

Obturation is an iffy thing, sometimes it happens and good results follow, other times it happens and bad things follow. Same for when there is no obturation. In a perfect world the would be no obturation- the boolit wild precisely fit the throat area and the powder would gently start the boolit down the barrel without distortion. That's why Harry Pope and Zischang and Schoyen and all the other old time lead boolit shooters used a false muzzle and muzzle loaded their guns. Most of us won't do that. We prefer fixed ammunition, so we try and hit a happy medium.

Different powders, primers, case shapes, throat shapes, seating depth, alloy, boolit design and size , rifling type and condition, even ambient air pressure can cause variations in the burn rate and pressure curve of a given load. SOME plain based boolits in SOME guns will be extremely forgiving of all those variables and will tend to shoot good up to somewhere around 2000 fps. At least those are the claims that have been made. You will occasionally hear of someone who gets 22-2300 fps for 5 shots or so. If this is true, these guys shouldn't even bother picking up a lottery ticket, they've used all their luck up!

In an average rifle those variables will stack up in a seemingly random order and usually limit your plain base shooting to under 1600 in general no matter how good a fit you have. That 1600 fps can be 1200 in some guns, 1700-1800 in others, larger calibers tend to be more forgiving. If, IF you go to a slower powder, a harder alloy, maybe a little larger boolit and a super lube and a filler you can up the speed. Maybe. It might work one day and not the next.

In handguns the PB generally works up to 11-1300 fps given good fit, etc as with rifles. Cartridges like the 45ACP can be used at factory velocity with PB with little problem, same for the 32 ACP and 380 ACP. Low pressure! Take a 9mm and you're good to a certain point and then it's lead city. Same for the 38, 357, 40S+W, 44 Special and Mag and of course the any of the other hotter rounds. Pressure seems to be the bad guy here and to me at least, it seems to work a little differently in handguns than in rifles.

A gas check just makes achieving higher velocity at a higher pressure easier. IMO boolit bases do not, and have never "melted". There isn't time enough , even under the pressures involved, for the heat transfer to take place. IMO what happens at the base is that the pressure pushes the lead around and like a rock thrown in mud there is some splashing. The rougher and weaker the base and alloy the more splash. Lead alloy is ductile and if you've ever hit an ingot with a hammer you can see that you don't get a smooth surface when you've hit it. I believe this takes place and the "splashed" particles are minute, maybe microscopic in size even.

The same general theory goes for the sides of the boolit once it's moving- only now you have hot gases trying to rush past the boolit through any gap between boolit and barrel. The alloy doesn't "melt", the gases abrade the boolit surface (and of course a rough barrel can help this happen too) and the particles of alloy are blown onto the barrel surface and pressed on by pressure. At least that's my understanding. There can also be the instance of lube failure where the alloy is actually rubbed into the barrel surface. I call it lube failure, but it may actually be something else.

So what does the GC do?

1- Provides a scraping action to the barrel. The edge of the check theoretically scrapes lead from the boolit ahead of it away from the barrel.

2- Provides a seal of sorts in a properly sized gas check/barrel interface. An undersized gas check is a waste of money. What the tolerance is depends on the gun and load, but as a general rule I want my checks at least bore size and preferably closer to groove size. If the check is under bore size it's effect is drastically reduced, may not work at all and is wasted money.

3- Provides a much stronger base to the boolit and one that remains square throughout the boolits journey up the barrel. This I've seen- seat a check crooked and shoot several groups with crooked checks and square checks. It don't take a genius to see the difference.

4- Makes achieving higher velocities at higher pressures EASIER. That doesn't mean the sky is the limit. There comes a point where the alloy can't take the pressure/velocity/rifling anymore and you get leading and wild shooting. But the GC makes it easier to go faster using pressure to boost speed.

That's my understanding at this point. 10 years ago I had a different opinion, 20 years ago it was different than that! I used to think hard, hard, hard!!! I thought that would solve all the problems. Not so. A GC won't solve it all either, but it does reduce the variables in most cases.

i agree completely with this good post..... couldn't have said it better myself:drinks:

[Scramjet]

I ran into a real time consuming situation this winter trying to reload lubed (powder sticking to lube) 240gr Lee gas check designed cast boolits that I did not gas check wanting to load from start to mid-range velocities.
Reason for not gas checking was I have a new 44 special & 44 mag that I want to start with slow load development stages and get used to prior to full strenght loads.
I ended up hand cleaning the lube from all the Lee cast non-gas checked bootlit bands by hand prior to loading. I've since looked into Lee Alox Lube push through sizing and lube set-up possibly their cast boolit design to follow.

[3006guns]

I'm just starting to play with 200 gr. GC boolits and no checks. The gun is a Japanese type 99 and my alloy is 2/1 lino to WW. Like many others here, I'm cheap! Gas check cost is getting way out of line.

I have yet to actually go out and shoot as our weather is barely getting to the tolerable stage, but I've been wondering......

When you think about it, exactly WHAT is the difference between a GC boolit without the check....and a standard .22 with a heeled boolit? Not much really, yet we expect to pick up a box of .22 rimfire and immediately pop squirrels out of the tree with little effort. Assuming the right alloy is used in our cast boolit and the velocity within reasonable limits, you should be able to do the same with your home brew loads.

Just theory.........................

[Tallyman]

I put a dab of lithium (automobile wheel bearing) grease on the base of each lead rifle bullet. I keep my velocities under 1800FPS, but have read where higher velocities can be achieved.

I use bullets lubed with liquid ALOX and add the lithium grease just before I seat the bullet in the case.

Extended shooting is no problem. I clean the barrel with a few patches soaked in Hoppes No. 9 and the barrel wipes out clean.

AND NO LEADING!!

[BulletFactory]

It is my understanding, that there should never be any oil or grease in the case, as it will damage the powder.

[Tallyman]

Anyone who loads reduced velocity cast bullet RIFLE loads KNOWS to top off the powder with a tuft of polyester balled up and pressed in over the powder. This keeps the powder packed against the primer for consistent ignition and acts as a contamination insulator. It burns up 100% in the combustion process.

Lithium grease remains a solid until it reaches a very high temperature. If you store your ammo in an environment hot enough to melt the lithium grease, powder contamination will be the least of your problems!

If you are really concerned, store your loaded ammo in a refrigerator with the bullets facing down.

Please note. . .I use lithium grease only in cast bullet rifle loads - have never tried it in handgun loads.

Try a few loads. . .you will be amazed at the results.

[BulletFactory]

Thanks for the tip I haven't gotten to reload rifles yet.

[GREENCOUNTYPETE]

I'm just starting to play with 200 gr. GC boolits and no checks. The gun is a Japanese type 99 and my alloy is 2/1 lino to WW. Like many others here, I'm cheap! Gas check cost is getting way out of line.

I have yet to actually go out and shoot as our weather is barely getting to the tolerable stage, but I've been wondering......

When you think about it, exactly WHAT is the difference between a GC boolit without the check....and a standard .22 with a heeled boolit? Not much really, yet we expect to pick up a box of .22 rimfire and immediately pop squirrels out of the tree with little effort. Assuming the right alloy is used in our cast boolit and the velocity within reasonable limits, you should be able to do the same with your home brew loads.

Just theory.........................

to expound on that theory , we stuff a soft lead conical over a pile of powder and drive 400gr conicals 1600-1800 fps form 50 cal muzzle loaders all the time

some 45 cal conicals leave the bore nearing 2200 still no leading

some are hollow base some are plain base

some get better accuracy with a filler of cream of wheat over the powder

but in general good fit , some lube , slower powder , and we do get the added benefit of putting the rifling on the boolit during loading

i even shot some Lee R.E.A.L's rifling engraved at loading with no lube on them this last winter , i had a pocket of them i intended to lube as i shot but alternating patched round ball then lee real i had no problem loading them or any leading , i even broke all the "rules" and cast them from strait air cooled wheel weight.

now i didn't put many of these on paper , several into the gong but not any extensive accuracy testing and all were fired off hand

[GREENCOUNTYPETE]

The bullet.
http://i388.photobucket.com/albums/oo327/303Guy/MVC-503F.jpg

I should stress that this is still early days!

wow no lube grooves at all very interesting

[Maven]

All, I primarily shoot homemade CB's with GC's in all of my rifle calibers except the .45-70. However, I've also been experimenting with PB CB's, e.g. the group buy Lee 30-150-TL as well as a few GC designs minus the GC. What I've learned thus far is that bullet fit, powder charge, pressure, and velocity have major effects on accuracy. E.g., with the .30cal. Lee TL CB, 7.5gr. Hodgdon Clays or 8.7gr. Alliant Unique will produce excellent accuracy and virtually no leading @ 50yd. (CB's lubed with Lee Liq. Alox). Btw, those CB's shoot as well "as cast," but sorted to remove obviously flawed ones, as they do if "sized" to .314" and lubed with Felix Lube.

As for shooting GC CB's naked, I've tried it, but wasn't satisfied with the lack of accuracy that ensued. That may have been my fault because I may have driven them too fast and because I gave up after a few unsatisfying tests. I.e., I don't want generalize based on a small sample. In spite of that failed experiment, I recently tried testing 3 different CB designs without GC's with generally favorable results.* The CB's were Lee #311291, Lee C-309-180-R, and Saeco #315. However, I didn't load and shoot them "as cast," but tapered them in a Hanned (Ed Wosika) Die.** Said die will expand the noses to .302", bodies to .3095", and entirely remove the GC shank, leaving a perfectly flat base. The Lee and Saeco CB's, especially the latter, performed very well with light powder charges, but not the Lyman. E.g., 19 out of 20 (1 flyer, entirely my fault) of the tapered Saeco 315's went into 1" x 1 3/8" @ 50yd. using 8.7gr. Unique and no filler of any kind. Although these were not strictly unchecked GC CB's, they were astoundingly accurate and something I'll certainly try again.


*Rifle was a Win. Mod. 70 Westerner (blind magazine), .30-06.

**I bought the tapering die, custom tailored to my rifle's throat because neither the Lee C-309-180R nor the Lyman #311291 fit my rifle. The Lee cast too small in both the body and nose (.299") while the Lyman had an undersized nose (.2985"). Gas checked and tapered via the Hanned Die, both designs shot into 1 moa, whereas before the dispersion was 2x - 4x as large.

[GREENCOUNTYPETE]

I was driving some c309-170rf at 1700-1800 today with 7 grains of grits filler and 25 gr h4895
but it did open up, however no leading

[Bulltipper]

OK, so I have to ask. If I am dedicated to shooting a subsonic .30 cal rifle boolit, and it is a gas check design- and I don't put a gas check on... At 1100 fps or lower, will I have an excessive cutting or leading issue or will this boolit behave like a boat tail and perform as such? I ask as I am shooting thru a suppressor and am looking for a boolit that will perform properly and expand without having to semi jacket swage up some custom stuff...

[windrider919]

I have seen leading at velocities as low as 700FPS.

But the bullet was .347 in a .355 bore.

And I have shot lead bullets, NO lube and NO gas check as fast as 1800FPS...20 shots and had no leading. The alloy was WW + 2%tin and water quenched. the bullets were sized .460 and shot in a .458 barrel.

Note that the .460 bullets also had a .040 PE wad under them.

Velocity is not the primary factor in leading, bullet fit is.

[barrabruce]

Bull tipper
My plinker load for me 30-30 is a lee 170fp.Gc with no GC
Leemented so the nose engraves on my gun which is a big big in the bore.
I use 3.5 4 grains dunno a 22 mag shell cut down of bulleye and a tuft of darcon.
tumble lubed with alox and seated til the bullet engraves the lands.
Has been chrono-ed to 950 fps.

I regularly get 1" groups at 100yrds and a hand span at 300
Less if I use premium cast and pay attention to the wind....on a good day.
I have used bees wax and lithium greese but it is messy to play with.

I most use me duds for this load with rounded bases or not filled out necks.

My twist is 1:12 it does show signs of wobbling but shoots good enough.

I fit it to my bore and +1-2 thou over groove.

When I get frustrated I'll hit the 300 mtre gong most the time. Flight time is about 1.5 seconds.
Bang ..wait for it..ting :bigsmyl2::redneck:
Gong is a 18" disk in a tire.

I think cast would be the ticket.

A teardrop shape is the sub sonic shape to persue.
I 've heard of loading backwards for long range but never tried it.

Haven't shot anything with it but paper effigies of critters cans and clays with it but.

[Bulltipper]

Barrabruce, sounds like fun, wish I could join you for a couple beers and some gong shooting!http://castboolits.gunloads.com/imagehosting/thum_113974e0cd14ebad4c.jpg ('http://castboolits.gunloads.com/vbimghost.php?do=displayimg&imgid=1339')

[scattershot]

barrabruce, thanks for the info. I have always wondered if my 311291 would work in a 30/30 without the gas check at low plinking velocities. I'll give it a try.

[Lead Freak]

I've been buying Lee molds, however they don't offer a boolit mold with a gas check base. Is there a way to use checks on boolits that dont' have gas check bases cast in? I'm specifically looking for a way to gas check a 9mm boolit.

[wiljen]

Welcome to the board.

With it being your first post, I have to ask, Do you cast for anything other than 9mm?

The 9mm is one of the most difficult handgun rounds to get to shoot well with cast because of the pressures involved. It can require tinkering with Alloy, size, hardness, lube, and powder charge to get a load that functions to the desired level.

If you have a 45 ACP or a 38 Spec, I would work with those first and take what I learned as I moved on to the 9.

The general wisdom is that a 9mm doesn't need a GC and Lee is not alone in only making plain base designs for the round. A quick check of RCBS, Saeco, NEI, and Lyman shows that none catalog a standard 9mm with a check.

There have been some attempts at making checks for non-GC designed bullets with varying degrees of success. You can try one of the designs that makes checks from coke can material and then size the bullet/check combo back down.

I would advise some tinkering with alloy and fit though.

The BHP I used to own preferred the 358345 sized to 358 cast of linotype or heat treated WW alloy.

[Joe504]

Lead Freak, me, Wiljen, and probably everybody else, is assuming you are asking about 9mm Luger. I only say this because Im tinkering around with 9mm Largo right now. If you are casting something other than Luger, you might have better luck with casting success. I am certainly not an expert, but from everything I have read, and from advice from a commercial re-loader friend of mine, Luger is very difficult to cast for.

[windrider919]

+ on all the comments on either the difficulty of cast with 9MM and with it not working well with a gas check.

However, if you simply MUST try it, I have used this method to modify a mould.

Mount the blocks in a mill... true and plumb... and cut the mould down between 0.090 and 0.100 so the bullet would be 'shorter'. Then make a pair of plates 0.100 thick ( most GC are 0.080 to 0.092 'high' so this leaves a slight gap between the top of the GC and the full dia bullet /shank which fills with grease like an intended groove, the first plates I made were too thin to work, warping and such) and just a little oversize to the mould block tops. Mount the set of blocks in the mill vise and establish edges and center over the bullet. Mount the plates with small pins and countersunk machine screws to the top of the mould blocks. Then, with the center of the quill shaft centered over the covered/hidden bullet cavity, drill a 0.340 hole...debur and try it. If you got everything centered you will have a shank for the gas check to mount on...the bullet weight will be lower.

Remember to index and drill any holes for sprue plates and stops that were originally there in the mould so it all goes back together correctly.

I have also done this with molds that were not cut down to get a heavier bullet, as long as you get it all centered so the new shank on the bullet is not lopsided/off center you can get as good of accuracy as from the unmodified mould.


Getting REAL crazy, if your machining skills are up to it, I experimented by using the cheap Lee moulds and used a 45ACP round nose tumble lube mould and combined it with a 45ACP SWC tumble lube mould...joined to each other base to base [ignore the outside block dimensions, getting the cavity edges true to each other within 0.0005 was the hard part. I then cut down the SWC end block until the meplat point of the SWC became the pour hole for the cavity. Installed one of the old sprue plates on the new cut surface and I ended up with a 415 grain Round Nose Boat Tail .45 rifle bullet for paper patching. It actually shoots pretty good considering what a B-astard kludge it is, with average groups being 1" @ 100 yds out of a .458 Winchester Mag at 2100 FPS.

Of course, using Pam for release spray and making glue gun sabots to protect the boat tail in firing that would still cleanly separate was a engineering TASK! It works but is just TOO MUCH trouble for the slight-ly better BC of the boat tail.

[Dthunter]

Hi guys!
Awsome thread!
Allot!, and I mean "ALLOT" of food/info for thought here!

I have an observation though.
(Great! More variables!) lOl!

Sorry for going a little off topic, but i would like to know your thoughts on this.

With the large variation of velocity with rifle cast shooting(1000-2500ish), that has to play heck with a given bullets ability to deliver top knotch accuracy.

By this, I mean, how can a rifle with a fixed rifling twist deliver top knotch accuracy over such a broad range? At some point there has to be a trade off.
I know for ranges past 1000 yards (with j-bullets), twist & velocity come into play "big time".
I wonder if going with a bullet more appropriate for the twist/velocity should be a cast shooters first concidreation. Then bore fit, and lube, etc.
Just some food for thought guys.

I hope my Rem700 Varmint .308win, will shoot MOA out to at least 4-500.
but that might be a bit much! Lol!

Push the envelope, thats where it gets interesting!

Have fun and straight shootin guys!

[jukar]

If your bullet is sized properly for your gun,
and if the pressure is sufficient to obturate the bullet per the bullet hardness.

Is there a need for a gas check? Even at elevated velocities?

From what I have been reading, I suspect the answer is, or could be no.

Although I also suspect powder burn rates may play a role in determining whether a GC is needed. Maybe it is simpler to use a GC and not worry with all the variables.

Please help me understand.

I have had good results making my owne 30 cal. bullets out of a mold that is ment to make gas check bullets.Then i liquid alox the bullets and load them up as to keep them under 2000 feet per second.I dont know what other guns it will work good in but mine works well.

[Bret4207]

Hi guys!
Awsome thread!
Allot!, and I mean "ALLOT" of food/info for thought here!

I have an observation though.
(Great! More variables!) lOl!

Sorry for going a little off topic, but i would like to know your thoughts on this.

With the large variation of velocity with rifle cast shooting(1000-2500ish), that has to play heck with a given bullets ability to deliver top knotch accuracy.

By this, I mean, how can a rifle with a fixed rifling twist deliver top knotch accuracy over such a broad range? At some point there has to be a trade off.
I know for ranges past 1000 yards (with j-bullets), twist & velocity come into play "big time".
I wonder if going with a bullet more appropriate for the twist/velocity should be a cast shooters first concidreation. Then bore fit, and lube, etc.
Just some food for thought guys.

I hope my Rem700 Varmint .308win, will shoot MOA out to at least 4-500.
but that might be a bit much! Lol!

Push the envelope, thats where it gets interesting!

Have fun and straight shootin guys!

There are several people that choose a twist based on boolit and velocity area. Most of us just don't have the option of choosing a particular twist and work with what we have. Regardless, twist is part of your fit, so fit always comes first int hat sense. There are multiple threads here about choosing a good candidate for a particular twist/velocity range.

Hope that helps answer your question.

[Tallyman]

I have found that a 1:12" twist in .30 caliber works best for me accuracy wise. My Remington Model 700 Varmint rifle has a 1:12" twist although most .308s and 30-06s come with a 10" twist. I also prefer a heavy .30 caliber lead bullet of 170 to 200 grains. I do not gas check my bullets, but lube with Lee liquid ALOX. After the lube dries I add a dab of lithium grease to the base of the bullet as I load it into the case. I keep my velocities under 1800FPS and my shooting range under 150 yards.

[nanuk]

I have to wonder if the reason GCs are needed above a certain velocity, with GC designed boolits or ANY boolit is that after a certain pressure, the base is deformed enough to not provide a similtaneous exit from the bore.

a damaged base will allow one side of the base to exit before another, and that is the same as having a predamaged base.

a GC is much harder, and the base edge simply can withstand much greater pressures.

one good experiment is someone needs to file a notch in a GC and see how accurate those are. it would support my SWAG

[a.squibload]

I was going to reveal my new adjustable-twist barrel
but not sure this is the right time...

[Westerner]

I was going to reveal my new adjustable-twist barrel
but not sure this is the right time...

I will stick with the tried and true "adjustable RPM" Barrel on my Pedersoli 1874 Quigley Sharps. Case in point; a 405 grain cast flat base flat point molly coated and lubed hard lead bore diameter boolit pushed at 1,100 fps in front of a max Unique load held in by dacron keyholed half the time. A minimum load of H322 left a dirty tube on the first shot and entered the target 3" high and 6" to the right of a 3 shot 3/4" group @ 100 yards. 1,600 fps = the magical 64,000 rpm. Never thought I would love a dirty powder. Never thought it could be done with iron sights either so I tried it all over and had the same results except it opened up a bit, to 7/8". This man loves a hair set trigger and a very long barrel with Soel long range sights.
[smilie=w:

[Larry Gibson]

I have to wonder if the reason GCs are needed above a certain velocity, with GC designed boolits or ANY boolit is that after a certain pressure, the base is deformed enough to not provide a similtaneous exit from the bore.

a damaged base will allow one side of the base to exit before another, and that is the same as having a predamaged base.

a GC is much harder, and the base edge simply can withstand much greater pressures.

one good experiment is someone needs to file a notch in a GC and see how accurate those are. it would support my SWAG

Sound reasoning and has a basis in fact. If the base of the bullet is below the case neck or there is a great amount of case neck expansion then the base of the bullet can "rivet" and not be square to the axis of the bore on exit. This can happen with PB and GC'd bullets. With the pressure pushing forward on the base of the bullet if the bottom driving band is not thich or strong enough it can be deformed as the edge is pushed forward in the lube groove above it.

Larry Gibson

[Larry Gibson]

10 and 12" twists in .30 cal allow a broad range of cast bullet weights to be adequately stabilized for accuracy over a large velocity variation, especially at the lower 300 - 2000 fps range. However, if you are entering the velocity range of 2000 - 2800 fps with medium weight .30 cal cast bullets then a 12 - 16" twist is better with the 14" twist being a good "median" choice.

If building a .30 cal rifle or rebarreling with HV cast bullet shooting in mind the 14" twist is my 1st choice.

On the other hand Bret is correct that "Most of us just don't have the option of choosing a particular twist and work with what we have." Understanding the rate of twist we have with a specific rifle and what is needed for accuracy at all spectrums of it's velocity range with a specific cast bullet is essential for best accuracy.

Larry Gibson

[ombesb]

Food for thought or comment. last summer I started shooting lead bullets from a revolver for the first time in my life. This was for low speed paper punching. Being new to this and having bricks for brains I made most every mistake one could think of. Soft bullets, very fast powder, undersized , loaded too light....... and painfully more. I was cleaning out lead with a hammer and chisel, jack hammers and various explosives. SLOWLY some thoughts , with lots of reading started me thinking. One of the first things I did that made a stunning reduction in leading was to long seat my bullets so they just barely started into the cylinder. I believe that is from the cartridge sitting on the bottom of the chamber and the bullet having to scrape up over the chamber end to start into the throat. Then I switched to a slower powder, from Titegroup, things got better. Finially, after months , I began to up my charges a little at a time. I had been trying to hold down low for reduced recoil. I got 2 results from bumping speeds up a little . Cases are now clean, no more burnt black sides and accuracy improved. Recoil went up a little but after a little while it made no difference at all. I am as slow and inaccurate as I ever was but the gun can now shoot 200 rounds with just barely a haze of fouling in the barrel.

[ShooterOnTheLine]

I guess we agree to disagree...

[NMLRA Guy]

Does anyone KNOW when you need to use gas checks and when not, what it REALLY does? My mentor Elmer Keith din't use them. Why do I need them??

[sixpointfive]

What about using gas checked typed bullets without the gas check for low velocity plinking?

[badbob454]

What about using gas checked typed bullets without the gas check for low velocity plinking?
this is what i do up to 16-1800 fps without , and above 1800 i use a check , however i have driven many a boolit in plain base near 2,000 fps with good accuracy my sks shoots a 175 gr boolit in plain base very accuratly @ 1800-1850 fps in a .314 diam boolit ...

[MT Chambers]

When IDEAL (Lyman) came out with gas checks, they and most everyone else tested them an awful lot, and the results are for us to enjoy not necessarily reprove. Results of their use can be seen in the record books, of course plain base bullets set records too, but are mostly breech seated and at lower velocity.

[PS Paul]

Does anyone KNOW when you need to use gas checks and when not, what it REALLY does? My mentor Elmer Keith din't use them. Why do I need them??

I know this an old thread, but I believe lasc.us had about the best explanation for using gas checks that I had ever read: to the effect...... gas checks are required when high SPEED and high PRESSURE are BOTH in play. Speed alone is not necessarily THE deciding factor.

[Lead]

Huh I've checked an if hard enough no cgi needed but softer needs gc

[stephen m weiss]

This is a good read. Bret comes closest to my view on this. I am new to cb and reloading in general, but did metal failure analysis in extreme environments and motion for 30 years. All of these issues show up elsewhere in machinery failure, manufacture or assembly.

Please forgive my nerd-speak and understand that I am just excited with this really fun topic. I do not intend to imply that ed-ja-ma-cation is in anyway a substitute for experience, especially in a topic like this one. These are musings, written like I write for fun, and I prolly sound like a pedant or some other horrid ting.

So, first my explanation of what is happening. Then my explanation of why it is so unpredictable.

The overall mode of failure is one of my favorite styles: kinematic instability with load and time dependent geometry and material properties. The radical inaccuracy comes from the bullet jack-knifing in the barrel as the sides overstress from pressure, heat, rifling friction force, and supersonic superheated gas errosion of material near the rifling contact line on the bullet. The still solid bullet is then wedged tightly cocked as hard as the gas pressure can get it, with the barrel itself eggshaped elastically from the load. As the bullet leaves the barrel, the last contact point catapults the bullet sideways with considerable spring energy that the barrel and bullet material have stored in the cocking. After that, the wind drag affects the bullet sideways according to the square of the speed and linearly with its cocking angle.

The situation is very similar to trying to do a hard press fit of a short dowel pin into a softer steel hole. The pin wants to go sideways, gouging the wall of the hole, and the more sideways it gets, the more off center loading it gets. The situation is worsened as the pin swells and fails due to heavy compressive stress.

With the lead bullet, the situation is so much more complicated. The lead is already very close to its melting point so addition of heat from gas and rifling friction interact with the above-yield stress state at the rifling to push the total lattice energy above the melt enthalpy.So the contact point lead leaves the area, allowing cocking.

It is so unpredictable because all these exponential effects are combining to eat away at the tiny remaining lattice stability of the lead. And when pushing a rod from the back it is always hard to predict when it will go sideways. The driving force, the powder explosion, is an instability in itself, and varies a lot from shot to shot, day to day, powder to powder. Finally, while we get to hear about the caliber, length and rifling of our barrel, we usually get no information on the surface roughness or actual dimensions of the land and non-land geometry. The non-lands are the flow paths for the superheated gas and grit to rush past the bullet surface adding heat and stress.

The good thing is that all of these factors do not involve chaos, relativity, atmospheric corrosion, or radiation. That aside, mixed phase flow, contact stress and friction, dynamic thermal material property change, phase change, three dimensional stress state, and deformation dependent loading are all some of the most challenging stress analysis modelling that can be accomplished, one at a time, let alone combined.

The tools to prevent cocking are packing, lube, fit, bullet engagement length, bullet strength and bullet melting point. Packing blocks high temperature gas from rushing past the bullet, adding their heat to the lead at its highest stress location. Gas checks are thermal and dimensionally stable packing, also acting as a 'hard point' for high contact stresses. Dacron polyester is a lubricious packing that blocks gas flow in the rifling non-lands. Paper wrap is packing. Really great fit means enough screw thread strength but not too much friction or compressive stress. Lube works as packing and reducing friction and wear. Longer bullet engagement reduces contact force on the rifling and minimizes the ability of the bullet to cock. Hard lead improves the strength and melt point but the best lead is still a dismal failure as a structural material especially around heat.

All of these solutions are in competition based on cost and effect. At one end the 22lr delivers 130ft-lbs at about 1.5 moa with an annoying pop for $.06. At the other end a 30 cal deer rifle with fmj reloads delivers 3000 ft-lbs at about 1 moa with an ear damaging boom for $.30.

Gas checks are $.03 and take less than 10 seconds to install. Polymer packing is nearly free and takes about the same time to install. The lead costs about $.04 per 150 gr round, and the best recycling systems are 50-90% effective, due to bullet destruction. The primer is $.03 and the powder is $.07-$.15. We all love making stuff, so labor is free.

As long as the lead rifling does not fail bad enough to make cocking cause accuracy loss, additional gas checks, packing, lube and bullet sizing are wasted.

Just my 2 cents on the really cool issue.

smw

[StratsMan]

This is a good read. Bret comes closest to my view on this. I am new to cb and reloading in general, but did metal failure analysis in extreme environments and motion for 30 years. All of these issues show up elsewhere in machinery failure, manufacture or assembly.

<<snipped for brevity>>

As long as the lead rifling does not fail bad enough to make cocking cause accuracy loss, additional gas checks, packing, lube and bullet sizing are wasted.

Just my 2 cents on the really cool issue.

smw

What a refreshing perspective, and I think I understood about 1/3 of it!! I don't agree with your conclusions 100%... At the very least, I like sizing for uniformity. Boolits from the same mold will drop and age to different diameters, depending on how well I do my part (consistent alloys, closing pressure, temperatures, etc...) One of my 30 cals shoots .309 boolits just fine, so if I stuff a .312 in there then the pressures will be higher, which will affect other things as well... Also, if I'm not careful about the diameter at the bore ride and make it too big, and it wedges in the bore, then I can't extract the live round... Forcing the bolt open sometimes results in the boolit staying in the barrel while the brass is removed... So, at the very least, I'm a fan of sizing when the boolit drops large...

[stephen m weiss]

I wanted to think carefully before replying. So, agreed, if there is gross mis-fit resizing is going to be possibly more important than any of the other factors.

There is this little equation I always remember: Ee=o, well little e is epsilon and o is little sigma.

E is the modulus of elasticity of the material. Lead and its alloys are about 2e6 psi.
e is the strain, diameter over diameter
o is the stress caused by the strain, in psi (pounds per square inch)

So in your case, that is 2e6 x (.312/.308-1)= 26ksi (1000 psi) well that squashes all lead. So, sending your bullet down the barrel with gas at 1500 atmospheres and god knows what temperature blasting up its shorts when it is already grossly squashed and failing would definately mean cocking. Fixing the fit with resizing would be the first order of business, as you have observed.

So, if any of the 'tools' are really badly wrong, fixing them first would be most important.

smw

[MT Gianni]

This is a good read. Bret comes closest to my view on this. I am new to cb and reloading in general, but did metal failure analysis in extreme environments and motion for 30 years. All of these issues show up elsewhere in machinery failure, manufacture or assembly.

Please forgive my nerd-speak and understand that I am just excited with this really fun topic. I do not intend to imply that ed-ja-ma-cation is in anyway a substitute for experience, especially in a topic like this one. These are musings, written like I write for fun, and I prolly sound like a pedant or some other horrid ting.


With the lead bullet, the situation is so much more complicated. The lead is already very close to its melting point so addition of heat from gas and rifling friction interact with the above-yield stress state at the rifling to push the total lattice energy above the melt enthalpy.So the contact point lead leaves the area, allowing cocking.

It is so unpredictable because all these exponential effects are combining to eat away at the tiny remaining lattice stability of the lead. And when pushing a rod from the back it is always hard to predict when it will go sideways. The driving force, the powder explosion, is an instability in itself, and varies a lot from shot to shot, day to day, powder to powder. Finally, while we get to hear about the caliber, length and rifling of our barrel, we usually get no information on the surface roughness or actual dimensions of the land and non-land geometry. The non-lands are the flow paths for the superheated gas and grit to rush past the bullet surface adding heat and stress.

The good thing is that all of these factors do not involve chaos, relativity, atmospheric corrosion, or radiation. That aside, mixed phase flow, contact stress and friction, dynamic thermal material property change, phase change, three dimensional stress state, and deformation dependent loading are all some of the most challenging stress analysis modelling that can be accomplished, one at a time, let alone combined.


Just my 2 cents on the really cool issue.

smw
Very interesting explanation.I have examined many hundreds of range pick up bullets, my own, others and commercial. I have never seen evidence of a melted base. The milliseconds that the temperature is there is not enough to melt them or most commercial lubes. Nor will the powder flame melt lead fouling.
Thanks for your insight on the equations of a booits stress.

[stephen m weiss]

I would expect you are right that it would not look like what we think as 'melting'. What would be occuring is the lead metal at the tail of the bullet that is squished by the rifling lands is at the highest stress. The heavier the squeeze, the larger this zone of material that is above yield stress. As the edges of this zone heat from the superheated gas, primarily at the back of the bullet, the rifling indents at the back would simply deepen as the bullet became more cocked. This would increase the stress concentration to just the corner, and deflection would increase. So, its not so much melting away globally, as losing the last little bit of strength in an overstressed contact point allowing worse cocking.

If the lead is smeared on the gun barrel, the barrel with act as a heat sink and protect it. Loose sharp edge shavings may melt in flight a bit. I have recovered melt globs of wax lube in from my barrel looking to see if there was leading. I guess the wax doesnt stick to the powder residue very well.

thx again!

smw

It is like shearing off the hot sprue just after pouring the mold is easier than waiting for the mold to cool completely. It's still shearing a solid metal not wiping away molten metal, its just easy and moves with little effort because there is little strain energy left in the metal, being so close to melt.

Thanks for adding your insights. Observations make the theory match much better.

I have recovered some heavy slow bullets that showed what I thought might be tail skidding (not melting) but since I shot into soft oil-sand, it's a bit hard to be sure what was done in the barrel and what was done in the sand. But I know I shot the heavy bullet kinda hot with no packing and it was starting to get inaccurate at a very short range (18 yrds) so I had trouble believing a low in flight stability could push it off course so far so fast. It seemed more like it never was going truly in the right direction. Then i shot some 223 50 grains at 2200 fps with no packing and many just plain came apart, and were 2 foot off course. This was obviously in-barrel damage. I expect those little bits were pieces of the tail that the rifling had filed away and spit out.

[stephen m weiss]

Oh, more anciliary evidence that tail rifling heating is important. If it were not, then it would take a tail gas check and a nose band to increase accuracy. But as we see, only .03 or so of rear gas check on an engagement length of .625 is enough to get very close to fmj speeds. Right? A gas check 30 cal cb can go 2600 fps where the mil spec fmjs of that weight are 2800 fps or so? Sure that fmj can go even faster, but full magnum bullets need a little tougher construction get smokin to 4000ish fps right?

I bet if you made up some copper wire spring rings and stuck em in grooves fore and aft on a cb, you could get all the way to fmj speed. Kind of like an ic engine piston. If i had a bullet sizer, i would make up some on a regular cb and size em into grooves shortly after casting and before oven water drop hardening. Its easy to make soft copper springs by winding around a drill bit shank 1/32 smaller than the bullet. Wind them long then nip to 2 turns or so. Turn in the nipped ends a bit to grip the lead so they cant spin.

Ha a test for a different day!

smw

[popper]

S.W. - I had thoughts of a 'plastic ring' for the base or wrapping the base in wire. Then I realized the hard ring (in your case Cu) would act just like the barrel. Gas cuts between ring & boolit. Time in barrel is microseconds, not milliseconds. No way you can get thermally applied heat to the lead. Pressure generated energy that is converted to heat, yes. I've shot 308W to > 1800 sans checks (PC so no leading) accuracy suffers from (IMHO) shank riviting. Same boolit > 2400 with accuracy when checked. GC also prevents base 'twist' damage. Lots of torsional force along the length of the boolit when pushed to twist. Once the GC is in the grooves, torsional force on the boolit is changed to compressive force.

[stephen m weiss]

Hmm, metal yield gas seals are some of the best. The copper will seal to the lead up to the compressive strength of the lead, and there may be some self energizing component. Even if there is leak because the gas pressure is so high, the flow rate will be very low because the gap is near zero. The gaps in the riflings are much larger. It's true the gc has the gas pressure to energize it to stick to the back of the bullet, at least until the bullet leaves the barrel.

[stephen m weiss]

mm time in the barrel is about twice of 2'/2000fps =.002 sec = 2 millisec. Doesnt really matter, until i dig out my time constant material notes, I dont remember off the top of my head what the time constant for little bits of stuff would be. Its in that order of time though. I think the corners of the steel rifling would heat first because steel is lower density, the corners stick out, and high strength steel has **** for thermal conductivity. Unfortuneately, those corners are yield strenght pressed into the lead bullet right at its highest stress location. So that would put the heat right into the lead.

I really need to test some of this. Unfortuneately, my bullet casting skill is still low, with lots of flaws. I dont have temp control or bottom pour, and there are visible flaws which cant help. LOl I am still using paper towels as flux. Worked good till the smoke alarm went off. haah

I am still doing most of the calculations in my head and havent developed my own spreadsheets yet. I developed simple hardness testing techniques in industry, but havent applied the better stuff to bullets yet, no jigs or fixtures yet.

Good to see you thought of the bullet rings also. Merits a test at least then. A bullet sizer is just one more Amazon purchase away! lol

smw

[MT Gianni]

Great thoughts. I had an old gun digest where someone modified a .375" mold to take 0.100" copper bands cut from 3/8 tubing. I don't know how fast you could drive them even in an H&H. That is an interesting concept.
I like the explanation of heat stressing the bullets rear rifling marks. Always something more to understand from our boolits.

[popper]

S. W. correct on barrel time, I incorrectly stated that. Time for high pressure is generally 1/2 mSec, depending on the load & powder speed. High pressure/small nozzle = high velocity which is the culprit for gas cutting, not the heat. Like a water cutter/plasma cutter. Mass & velocity do the work.

[stephen m weiss]

Y'up Popper. mass and velocity means energy aka work so agreed energy means moving material. The more I read of your views and expanations, the more i get the feeling we are using different words for the same concept. Just as gas solid liquid have no use at teh eutectic point, there is not much point in debating material failure so close to the strain-melt point. It is an energy controlled process.. so cutting off the energy causing failure is one method, ie packing while another is raising the energy required to fail, ie fmj is another. A method that does both at once is golden, ie gas checks.

This of course does not mean that there are not more cost efficient methods. Also different methods have secondary advantages. Toilet paper versus Dacron (polyester) packing is one such issue. They are nearly identical materials. However, since polyester is basically chemically immune, toilet paper packing will be gone from my land many years before teh poly-fuzz would be.

I cant wait to test copper rings. I have a bunch of 18 ga wire.....

smw

[popper]

post the results, I'm interested. I use dacron, the TP is a fire hazard here in drought stricken country.

[rsrocket1]

Very good estimation smw,
Looks like total muzzle time is around 1.8 milliseconds:
117392

[Metroxfi]

I had a thought on leading due to the bullet skidding/smearing on the rifling... A while ago I had read about guys making soft nosed cast bullets for hunting by casting with wheelweight alloy and water dropping, then put the bullets nose up in a pan and fill the pan with water until it came up to the nose section. They would then take a torch and heat up the noses to undo the heat treating from the water dropping on the nose section only, so you have a hard base/driving bands and a softer/expanding nose section. What if you did it the other way around and heat treated the bullet then softened the rear driving band? That way you'd have a solid front band that wouldn't skid as much and you could also benefit from obturation, a sort of 'best of both worlds'. Or is that too much trouble for little to no reward?

[stephen m weiss]

I think the rear driving band, just where the gas check would sit, is the most critical for keeping the bullet stable in the barrel, and you want that hard and slippery, like copper.

[rsrocket1]

Here is a picture of my last outing with cast 30 cal boolits. 36 shot and a clean shiny barrel. I have to admit that 10 shots were with a gas check (the 800X loads) so that may have cleared any leading, but the last 12 shots were at subsonic velocities with the 200g bare based bullet with 6.5g Red Dot. Max velocities was in the mid 1600's with the 113g bare based bullets.

I have a bunch more loaded with Dacron tufts to see if MV's change. 10g Unique seems to be pretty position insensitive however. After that I will work up to 2k fps to see how the 113g bullets hold up with bare bases.
118006

[stephen m weiss]

Very nicely done rsrocket! So, if I am seeing correctly, you are getting 2-4 moa with bare base bullets using unique and 800x.

I shot over the weekend and my cast bullets were hitting 8 moa at about the same speeds using TP packing and wax lube with 2495 powder. The bullets are not sized and have a lot of visible flaws because my process is still pretty bad. But higher than 1600 fps and the accuracy began to drop off sharply. A flawed bullet will of course be much more prone to canting in the barrel from eccentric center of gravity and missing material at the driving band.

I would be quite happy with 2-4 moa by comparison! So, I think I need a bullet sizer and single press, bottom pour temperature regulated pot, proper flux, and need to water drop from the mold.

Thx again, smw

[stephen m weiss]

Oh, when I did not use TP packing, i got very aberant speeds, like 0-20%, and some muzzle flashes.

[stephen m weiss]

I finally got a round to calc'ing the time constant for lead. I ran this years ago for the condition of a plate beginning heating at time zero on one side, what does the temp on the other side do? For a cylinder its gonna be much faster, or about the same if heated from one end like a bullet with perfect seal in the barrel. The equation is:

Time Constant = (4 x specific heat x density x thickness^2)/(pi^2 x thermal conductivity) = .18 sec/m^2 for lead.

The values can be found in wiki for common elements. Alloying changes the value. 6% Sb is about 16% slower, or larger. Time constant means the time to change 63% toward the surface heating temperature. Note that this may well be limited in practice by the convection doing the heating, especially in gas heating systems, like just-cast bullets cooling on the bench.

Some example thicknesses> for a 223 heating on the diameter, with no packing, time constant is about 2 msec. That means the 2 msec in the barrel combined with the thousands of degrees of gas temperature means that some surface lead heating at the rifling definately occurs. More justification for using good packing.

For a 308, that number is about 5 msec, so much less subject to in-barrel heating.

This also shows that cooling during water dropping is convection limited, or else water dropping would never work, the bullet would be cool before it hit the water. In this case, it is surface area to mass ratio that limits cooling, so a 223 will cool faster by 308/223 = 38%. So water dropping is gonna work, ya just gotta have them hit the water quicker by 38%.

If anyone wants to geek out on how much cooling occurs in the air, cooling power = 7 Watts/m^2/C for still air. You can get the density and specific heat from wiki. The surface area of bullets is pretty simple.

[popper]

convection limited Nope, conduction. Convection is due to moving heat absorber. Thermal resistance of air is much greater than water. 308 needs to be dropped into colder water (I'll accept your 38% number) to get same effect as 223, delta F controls the heat removal RATE, which is what makes W.D. work. I will agree, get then from the mould or oven as quickly as you can. Takes me ~ 5 sec max to dump the tray from the oven.

[stephen m weiss]

I guess i spoke unclearly. It seems we agree, just not on the wording. :)

In order for water dropping to help, the bullets need to be still hot when they hit the water. If the cooling in air was conduction limited, air quenching would be faster than the time to get them to the bucket. I was just speaking of the air phase. Clearly in the water, at 1000x the convection rate, conduction is doing the limiting. If the bullets were small enough, they would air quench just fine. If they were big enough, even the water would be unable to quench them fast enough. It would only require the 2nd or 3rd root of 1000 times bigger, so maybe 3 inches diameter. In that case, only surface hardening would occur.

Let me dig out the time constant equation for convective cooling. I can determine roughly how long is ok to take from teh oven to the water. They actually solved that problem in my book and I did not have to derive it myself. ahahah

Say popper, I have been using my 10x steroscopic microscope to inspect my 223 bullets. What size in cubic mills visible flaws do you reject for? I am just sort of using a general 70% rejection at this point. My 223 mold has lots of issues, like slipping alignment pins, wave washers dont hold down the sprue plate well, wood handles slip off the metal part...It's like herding cats to get good casts. lol

[popper]

I have never seen evidence of a melted base

That means the 2 msec in the barrel combined with the thousands of degrees of gas temperature means that some surface lead heating at the rifling definitely occurs
Not much. Joule content of a 150 gr boolit is ~1J @ 60F. Joule gain from a 2000F source for 1/2 millisec is ~6.8e-5 (sorry, bad number 1.7e-11). Multiply by 4 for 2 millisec time still is VERY SMALL. Temp rise of boolit & barrel is mostly pressure related. Boolit is compressed and barrel is expanded. There is a frictional component.
I inspect for any 'smiley face' wrinkles, sharp corners (fillout) & pits. Any visible(bifocals) surface defect. I did some weight sampling, most shot the same.

[LuckyDog]

Being a geek myself, I was sad to see stephen and popper stop posting in this thread......

[P Flados]

I have not seen much discussion of systematic approach to "no-check" shooting with PC to get decent velocities without the check.

This year, I started PC and now have 3 gas check molds



C358-200-RF

C309-150-F

C309-170-F

​
I have been working the 308 stuff up for 30 Herret (10" TC & 14" TC), the 357 will be for 357 Maximum (8" DW & 10" TC).

All without checks. Most with straight wheelweights.

Just started on the 358-200-RF. Pushed it pretty hard and it seems shoots as good as any flat base has.

I have done quite a bit with the 30H. So far, if I push too hard the accuracy goes out the door. With moderate loads, accuracy is as good as I have been able to get with cast bullets. I probably could do better on velocity with some babbit mixed in (for Cu) but have not been willing to buy the babbit. Velocities look good enough for for my goa (I hope to get back into IHMSA some day).

Any pushing the "no check" option with PC?

[popper]

I I'd test a couple years age, GC/sans GC in 30/30. With the alloy I was using and 2400, unique and LeverE, no check limit seems to be 1600 or so. ESPC of course. I've gotten to 1800 modified PB, PC before accuracy losses. I've got an alloy now with ~34 BHN to test, I'll try sans GC in 308. It's 2% tin by weight, replaced by Cu so 2% Cu, heat treated, ~4% Sb. Results in copper thread.
Edit: Larry G's XCB tests, where GC fell off during firing, provide evidence it is the pressure related heat/weakening of the alloy, not flame temp that destroys the base. As I commented earlier, it means the shank gets rivited on firing that destroys accuracy. Additional evidence from my modified PB boolit ( really short GC shank) the pressure related soft alloy base deforms at the crown and accuracy suffers. Got to cast some for the BO with this hard alloy to see if the accuracy improves past 1800 fps. Of course it doesn't 'bump up' to seal very well so I get to try with various sizings also.

[Doggonekid]

I just got in a new boolit mold from RCBS. It is a 300 GR SWC .452 GC. I casted up a few rounds tonight. I want to run them through my .460 Mag. I will run them with GC and with out. I also will PC with GC and with out. Once I have some results that work for me I will post again on this tread. I'm not expecting a huge difference either way. I do expect some difference I'm just not sure how much. All of my other guns GC or not does not seam to make a difference. I just plink at soda cans from 25 to 50 yards. I like the option of having a GC mold. I can put one on or not. Non GC molds I have no option. The faster the boolit the more I try to get GC molds.

[SniderBoomer]

So...what ever happened to progressive Rifleing?


I heard the Colt Dragoons had it...various Rifles of course did back when.


What about now?


All these 'skidding' woes could become a thing of the ( recent) past!


Damn, that's a good question, worthy of reply from some barrel makers.

[P Flados]

I finally reached "happy" with my PC coated Lee C358-200-RF as checkless. Sub 3 MOA and around 1500 fps from a TC 10" 357 maximum barrel.


http://castboolits.gunloads.com/showthread.php?283606-New-LEE-design-358-200-RF&p=3459027#post3459027

[natty bumpo]

i am certainly no expert, in fact, this post will certainly show how little i really understand about these. but i always thought that gas checks should be doubled up. like welded together, back to back. one side crimped on like they do, the other side facing backwards so they would act like a bevel base bullet. sealing all of the gas pressure behind the bullet. kind of like this.... ><bullet

GENIUS !!!! (bear in mind that I am a complete moron when it comes to these things) BUT GENIUS !!

[nitro-express]

If your bullet is sized properly for your gun,
and if the pressure is sufficient to obturate the bullet per the bullet hardness.

Is there a need for a gas check? Even at elevated velocities?

From what I have been reading, I suspect the answer is, or could be no.

Although I also suspect powder burn rates may play a role in determining whether a GC is needed. Maybe it is simpler to use a GC and not worry with all the variables.

Please help me understand.

I have somewhat limited experience shooting gas checked bullets, and still have a lot to learn. I've used 1000 of each in 44 and in 35, plus several hundred in 38-55.

Using a gas checked bullet can increase the flexibility of a load. I had 3 Vaqueros in 44 mag and a '92 SRC in it as well. Typical for production revolvers, the throats and groove diameters varied considerably. Rather than load 3 or perhaps 4 different loads, I found a load, with a gas checked bullet, that would work in all of them. Actually, one of the Vaqueros was not close in size to the other 2, so rather than facing the challenge, I sold it.

Almost the same story with my 2 357 Magnums, rather than having 2 different batches of ammo, I use a 358156 load that works in both. One of the guns, a New BlackHawk will shoot well with any decent load. However, the other, a Colt New Frontier, Gen II, doesn't seem to like anything but a 358156 gas checked bullet.

I've found hat a gas checked bullet will still work well even if it is undersize for the throats of the cylinder. Whereas a plain base one appears to work best at or larger than the throat.

Playing with hardness and pressure is almost a "Mug's Game" IMO. Lead alloy bullets mostly harden with age, some soften. Powders burn at different rates, and the pressure curves can vary, and sometimes a higher "peak" pressure load, may not obturate enough to seal the throats, but a lower "peak" pressure load will. Alliant 2400 is about the most forgiving powder I have used, in the 44 and 357 Mags. If given half a chance it will work well with plain base bullets. Ideally a load, to be considered a good load, should work well within a range of powder charges, bullet hardness and size.

I've concluded that gas checks are useful, especially for a beginner, as good results can be obtained easier and sooner with gas checked bullet than with a plain base design. The same can be said for PC (Powder Coated) bullets. Different theory, similar results. A gas check limits the effect of blow-by, less spray welding of the forcing cone, helps the bullet follow the rifling and tends to clean the bore of lead. Hardening, heat treating, cast bullets works as well, another useful tool.

I think you already have a good understanding of what is required, "sized properly", "pressure is sufficient", and "powder burn rate" are all important factors. And "Maybe it is simpler to use a GC and not worry with all the variables." is precisely what my experience tells me.

Using a gas checked bullet allows me to use the same bullet for revolver and rifle, in a range of velocities from 900 to 1600 fps, and in revolvers with 430 > 432 throats and 428 > 4295 grooves, and in a rifle with a bore/groove that I haven't bothered to check.

I still experiment, with different loads, with different gas checked and plain based bullets, with some success. But I do have one load that will work well in all. BTW, the bullet that I use is a Lyman 429434, a mold designed for the 44-40 rifle.

[nitro-express]

Very interesting explanation.I have examined many hundreds of range pick up bullets, my own, others and commercial. I have never seen evidence of a melted base. The milliseconds that the temperature is there is not enough to melt them or most commercial lubes. Nor will the powder flame melt lead fouling.
Thanks for your insight on the equations of a booits stress.

I have picked up quite a few bullets that had lead missing from the base. Blow-by will melt lead. Blow-by will melt as the velocity significantly increases the temperature of the powder flame. That is why sealing is so important. I have an automotive engine background, poorly sealing piston rings will lead to blow-by, and although combustion temperature is below 1200 deg F, blow-by will melt aluminum pistons and burn moly and stainless rings.

Something to try, Take a deep breath, now blow it out with your lips sealed as tight as you can, when your breath rushes out it will burn your lips. Yet your breath is not of hot enough to do that. The wings and the airplane flying at Mach will get hot, even in near freezing air. A meteorite will burn up when entering the atmosphere, and Hornady discovered that ordinary plastic tiped bullets with melt with velocity. All physical facts.

And unfortunately, powder flame doesn't seem to melt lead fouling, it just seems to solder on more lead.

[BAGTIC]

That seems strange as the laws of physics tell us that as gas expands it cools. Likewise as gas is compressed it heats as when it strikes the wings of an airplane.

[AKholicBubba]

At the moment, i don't shoot at really high velocities. But this is good for when ido

[Alferd Packer]

The first thing at any and all velocities is the fit of the bullet to the bore. After that the variables increase with pressure and velocity. Out to fifteen yards for instance, a smoothbore can shoot small groups or scatter the bullets like a shotgun. It all goes back to the fact that each individual firearm id a law unto itself and shooters whorealize that fact also know that shooting naked lead with or without gas checks or paper patching are embarking on a quest or adventure or heartbreak when trying for ? Accuracy, velocity, or a properly musroomed hunting bullet or not.The Holy Grail in the case of each firearm. The right alloy, matched to the right powder, matched to the right velocity or pressure.
The neverending story. I love it and thank my Creator for leaving this on the table for me. Now with the closing of the last US lead mine in Missouri, we rely on recycling, which has become a sometime thing. All part of life's equation I suppose making it harder to blend alloys if you are so inclined in the chase to make your firearm perform.
It's a great game but we should all accept that its varied answers when found can and may change with each pull of the trigger.

[Alferd Packer]

You shoot a lead bullet at too great a pressure and you will get jets of hot gas blowing by melting the sides of the bullet gas check irregardless.
Proper pressure for lead bullet, bullet too small, blow by again, gas check or not.
Every gun is a law unto itself.
To shoot lead bullets without leading is cause to celebrate but bragging is pitiful. What works for you is good to hear. We all know what doesn't work or will discover in short order.
But there is no magic, only guidelines that can be ignored and sometimes you get away with it.
Not because you are smarter or have discovered something new, but rather you have discovered something old that was known by the oldtimers and its just that every gun is a law unto itself.

[GONRA]

GONRA noted "fillers" (TP, Dacron) mentioned above. Remember these are dangerous / tricky in bottleneck cartridges. Safest to Just Not Use "fillers" guys...