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Thread: Gas Check Boolits without Gas checks ???

  1. #21
    Boolit Master crabo's Avatar
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    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?
    Crabo

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  2. #22
    Boolit Grand Master 303Guy's Avatar
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    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!

    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).

    This shows how the bullet was lubed.

    This shows how a gas check did not help in a rough bore.

    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.


    The bullet.


    I should stress that this is still early days!
    Last edited by 303Guy; 03-21-2009 at 01:45 AM.

  3. #23
    Boolit Master 243winxb's Avatar
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    Obturation is Not Wanted Or Needed

    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.
    Last edited by 243winxb; 04-04-2009 at 08:36 PM.

  4. #24
    Boolit Master 243winxb's Avatar
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    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.

  5. #25
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    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.

  6. #26
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    Quote Originally Posted by MT Gianni View Post
    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!
    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!
    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.

  7. #27
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    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.

  8. #28
    Boolit Master Slow Elk 45/70's Avatar
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    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
    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.
    Slow Elk 45/70

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  9. #29
    Boolit Buddy Fire_stick's Avatar
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    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 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.
    He who knows best knows how little he knows.
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  10. #30
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    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.

  11. #31
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    Quote Originally Posted by Fire_stick View Post
    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 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!

  12. #32
    Boolit Master Hanshi's Avatar
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    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.

  13. #33
    Boolit Master Slow Elk 45/70's Avatar
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    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. 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
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  14. #34
    Boolit Master Hanshi's Avatar
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    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.

  15. #35
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    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?
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  16. #36
    Boolit Man
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    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

  17. #37
    Boolit Bub
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    I'm with OI. What happens when you shoot GC Boolits without GCs at low velocities?

  18. #38
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    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

  19. #39
    Boolit Buddy windrider919's Avatar
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    Reality vs campfire talk

    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.

  20. #40
    Boolit Buddy windrider919's Avatar
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    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.

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Abbreviations used in Reloading

BP Bronze Point IMR Improved Military Rifle PTD Pointed
BR Bench Rest M Magnum RN Round Nose
BT Boat Tail PL Power-Lokt SP Soft Point
C Compressed Charge PR Primer SPCL Soft Point "Core-Lokt"
HP Hollow Point PSPCL Pointed Soft Point "Core Lokt" C.O.L. Cartridge Overall Length
PSP Pointed Soft Point Spz Spitzer Point SBT Spitzer Boat Tail
LRN Lead Round Nose LWC Lead Wad Cutter LSWC Lead Semi Wad Cutter
GC Gas Check