What's the secret for PB success?

[Marlin Junky]

What is the secret to plain base success? Is it possible to do about 1500fps using a BN case and no filler? With my M77 .350, I've tried bullets in the 28 to 30 BHN range with small doses of pistol and shotgun powder using bullets from about .0005" to .002" over groove diameter and all I get are bad groups and leading near the chamber. Lube is LBT Soft Blue. I have been heat treating bullets to way over the point of obturation (I know this from QuickLoad) and launching them over bore diameter thinking the gas seal with the powders I've been using is sufficient. Where am I going wrong? Is it just that the edge of a PB's base is too fragile (no matter what the BHN) to withstand any significant pressure? With the powders I have on hand, I've gone down to about 15K... any lower and I start to get large extreme spreads in velocity.

MJ

[45 2.1]

What is the secret to plain base success? The correct alloy for the intended purpose. Is it possible to do about 1500fps using a BN case and no filler? With my M77 .350, I've tried bullets in the 28 to 30 BHN range This is way too hard. Try 50%Pb/50%WW and use a low viscousity lube. NRA and LBT are not low viscousity lubes. You might try Lyman Black Powder Gold..........or make the old NRA lube. with small doses of pistol and shotgun powder using bullets from about .0005" to .002" over groove diameter Throat diameter - 0.0005" is a good place to start for body diameter. Use a boolit which nose engraves. and all I get are bad groups and leading near the chamber. Lube is LBT Soft Blue. I have been heat treating bullets to way over the point of obturation (I know this from QuickLoad) and launching them over bore diameter thinking the gas seal with the powders I've been using is sufficient. Where am I going wrong? Is it just that the edge of a PB's base is too fragile (no matter what the BHN) to withstand any significant pressure? Its not with the right alloy, but you might try Freechecs also, they will give about 1900 fps with PB boolits with excellent accuracy. Fit needs to be good for this. With the powders I have on hand, I've gone down to about 15K... any lower and I start to get large extreme spreads in velocity.

[Marlin Junky]

.45 2.1,

Can you explain the mechanics behind "not the right alloy"? Is some obturation necessary when using PB bullets? If I understand the mechanics, then perhaps I can put QuickLoad's pressure data to good use when concocting handloads.

Not completely on the subject but nevertheless still a concern:
I don't want to use bullets that are so soft they are downsized when seating into case necks. By comparing the diameters before and after seating (of a pulled bullet), I've noticed that necks on several types of cartridge cases (e.g., '06 and belted magnums) can downsize BHN 10-11 bullets when seating into the cases. I suppose the combination of a little harder bullet and maybe a little bigger custom made expander would probably cure this but I've already got a drawer full of Lyman M-dies so it's not like I'm using all the wrong tools!

Thanks,
MJ

[pdawg_shooter]

Try paper patching. If you can do it with jacketed you can do it with paper.

[docone31]

I second paper patching!
I get better with paper, than jacketeds.

[mpmarty]

My best results are with straight WW and some added tin to fill out mold air cooled.
Pistol powders such as 700X, Red Dot, and even Unique don't work well for me at all with PB over about 1200fps. 2400 and 4198 seem better able to "softly" accelerate the projectile down the barrel. I believe leading at breech end is indicative of too much pressure too soon from fast pistol powders and leading at muzzle end is lube related. Contrary to some manuals I never use magnum primers with 2400.

[Marlin Junky]

My best results are with straight WW and some added tin to fill out mold air cooled.
Pistol powders such as 700X, Red Dot, and even Unique don't work well for me at all with PB over about 1200fps. 2400 and 4198 seem better able to "softly" accelerate the projectile down the barrel. I believe leading at breech end is indicative of too much pressure too soon from fast pistol powders and leading at muzzle end is lube related. Contrary to some manuals I never use magnum primers with 2400.

My worst groups so far have been with WC-820 and 2400 and I'm talking less than 14K PSI (according to QuickLoad). 45-2.1 probably has the best advice but I still need to understand the mechanics of matching plain base BHN to PSI. The rules (whatever they are) probably still pertain to GC bullets but we can get away with ignoring them somewhat when gaschecking our bullets.

Paper Patching is good but I want to be able to put together some types target/varmint ammo quickly.

MJ

[Larry Gibson]

I agree for the most part with 45 2.1's comments. Only exception being on lube and that is only a partial disagreement. I've used the standard NRA 50/50 lube (mostly Javelina but several other makes as well) and also LLA with true PB bullets(Those with flat bases designed as PB'd bullets).

I'll also suggest that your selection of powders is not correct, they are both too slow burning. Suggest a switch to Unique, Universal or Power Pistol for loads from 1200 up through 15-1600 fps if the bullet is a normal for caliber weight. I mostly use Unique for such loads and haven't found a need for a filler or wad.

If you are using 160 gr or less weight revolver bullets then I'll suggest Bullseye. Start with 4 gr and work up. Again, no filler or wad necessary.

Larry Gibson

[rhead]

.45 2.1,

Can you explain the mechanics behind "not the right alloy"? Is some obturation necessary when using PB bullets? If I understand the mechanics, then perhaps I can put QuickLoad's pressure data to good use when concocting handloads.

Not completely on the subject but nevertheless still a concern:
I don't want to use bullets that are so soft they are downsized when seating into case necks. By comparing the diameters before and after seating (of a pulled bullet), I've noticed that necks on several types of cartridge cases (e.g., '06 and belted magnums) can downsize BHN 10-11 bullets when seating into the cases. I suppose the combination of a little harder bullet and maybe a little bigger custom made expander would probably cure this but I've already got a drawer full of Lyman M-dies so it's not like I'm using all the wrong tools!

Thanks,
MJ
You are right that it is the size of the bullet as it leaves the case not the size before loading. You need to fit the chamber and leade also. Have you measured the neck area of a fired, unsized case? Inside and out? You may have an oversized chamber.The bullet might be getting damage before it gets to the rifling.
You may have more success by using an expander plug that fits the bullet you need instead of trying to use a bullet that is hard enough to withstand a too small expander plug.

[Marlin Junky]

I agree for the most part with 45 2.1's comments. Only exception being on lube and that is only a partial disagreement. I've used the standard NRA 50/50 lube (mostly Javelina but several other makes as well) and also LLA with true PB bullets(Those with flat bases designed as PB'd bullets).

I'll also suggest that your selection of powders is not correct, they are both too slow burning. Suggest a switch to Unique, Universal or Power Pistol for loads from 1200 up through 15-1600 fps if the bullet is a normal for caliber weight. I mostly use Unique for such loads and haven't found a need for a filler or wad.

If you are using 160 gr or less weight revolver bullets then I'll suggest Bullseye. Start with 4 gr and work up. Again, no filler or wad necessary.

Larry Gibson

Larry,

Let's forget about lube for the time being... I need to get under 3MOA then I can tweak my lube.

I've had equally bad results with #5, 231, and Scot 453... all faster than Unique. I'm under the impression the fundamentals are matching the alloy to the pressure or maybe even the area under the pressure curve but I don't know how to do it. I'd also like to understand the physical process when a bullet too hard for the pressure, enters the throat a thou or two over groove or throat diameter.

The next time I pick a powder charge using QuickLoad that develops about 1500 fps (while burning completely) I'll divide the PSI by 1440 to determine the "proper" BHN value. For example, if I use 14 grains of 231 in QuickLoad, I get 1516 fps and 22798K PSI which is telling me to use a bullet with a BHN of 15.8. Now, what I absolutely don't know about this pressure: is it equivalent to the threshold of obturation, or at least the approximate threshold AND (assuming it produces an accurate load) why does it produce a more accurate load than one using a BHN 29 bullet? Or perhaps the better question is: why does it not lead like mad near the chamber as the load with the BHN 29 bullet does?

MJ

[Larry Gibson]

Marlin Junky

Let's forget about lube for the time being... I need to get under 3MOA then I can tweak my lube.

Okay, I'm good with that as odds are it really won't make that much difference as LBT Blue should be good at 1500 fps.

I've had equally bad results with #5, 231, and Scot 453... all faster than Unique. I'm under the impression the fundamentals are matching the alloy to the pressure or maybe even the area under the pressure curve but I don't know how to do it. I'd also like to understand the physical process when a bullet too hard for the pressure, enters the throat a thou or two over groove or throat diameter.

In my post notice I recommended Unique basically from 1200 to 1500 fps. The faster powder (Bullseye) was for accurate loads up through around 1200 fps. I disagree with the concept of matching the alloy to the pressure. I've found I can shoot some pretty soft alloys accurate at a lot higher pressures than is recommended by a couple loading authorities. What I do believe is the alloy should be matched to the acceleration or time/pressure curve. Many of us regularly shoot PB bullets to 15-1600 fps cast of pretty soft alloy like 1-20 or 1-16 tin-lead. I shot a lot of PB GB325190s out of my 8x57s and 375248s out of my .375 H&H. Most of those two bullets go out at 1450 fps loaded over Unique and accuracy is definitely sub 3 moa. I also have pushed the 375248 cast of WWs + 2% tin and WQ'd to 1600 fps before accuracy went but that was with a dacron filler also and 4759 powder.

Now I also shoot several bullets out of my 45-70 TDs in the 1350-1450 fps range with 2 moa accuracy. These are 458124 and the Rapine 460500. Those are generally cast of range lead + 5% tin. I have pushed a 413 gr commercial cast bevel based bullet to 1550 fps before accuracy went but again that was with 4895 and a dacron filler. I also shoot a 375 gr .50 cal MaxiBall cast of 1-16 tin-lead alloy out of my TC Black Mountain Magnum at 1525 fps with excellent accuracy.

Now as to .35 caliber rifles I do not have a .350 Rem Mag but I do have a M91 Mauser with a 26" Shilen barrel on it in .35 Remington. It shoots cast bullets 99% of the time and it shoots them well. I shoot two PB bullets in it. A Lee 358-120-TC and Lyman’s 358477 which goes out over a very mild load of Bullseye for 1170 fps and 2 moa accuracy. The 358477 goes out over 8.5 gr of Unique for 1440 fps and the same 2 moa accuracy. The Lee bullet is generally cast of range lead + 5% tin (BHN 12-15) and the 358477 is generally cast of WWs + 2% tin (BHN 12-14).

The next time I pick a powder charge using QuickLoad that develops about 1500 fps (while burning completely) I'll divide the PSI by 1440 to determine the "proper" BHN value. For example, if I use 14 grains of 231 in QuickLoad, I get 1516 fps and 22798K PSI which is telling me to use a bullet with a BHN of 15.8.

Regardless of the "pressure" the acceleration/time/pressure curve is too fast for a PB'd cast bullet even of that BHN. Also it's all nice to calculate and "pick" a load but the problem is the rifle is not in on that calculation and "pick". There are many things in the rifle that the computer program does not take into consideration.

Now, what I absolutely don't know about this pressure: is it equivalent to the threshold of obturation, or at least the approximate threshold AND (assuming it produces an accurate load) why does it produce a more accurate load than one using a BHN 29 bullet? Or perhaps the better question is: why does it not lead like mad near the chamber as the load with the BHN 29 bullet does?

Let's take a different tact here; take one of your cast bullets and holding it between thumb and fore finger push an open door shut with it. There will be little to no obturation to the bullet and no damage to the door. Now open the door back to the same position and place the bullet against the door. Now smack the base of the bullet with a hammer until the door is closed. You should now see some major obturation to the bullet. Both the push of the bullet with your hand and the push of the bullet by the smack of the hammer represent two different acceleration rates or different time/pressure curves. The first is with a slow steady pressure as represented by slower burning powders. The second with the hammer is the much quicker fast burning powders. The resistance of the door to both applications of pressure represents the inertia of the bullet just before it is fired. The effort to close the door remained the same but two different applications of accelerations (time/pressure curve) resulted in two different amounts of obturation to the bullet.

It is the same when the bullet is fired with equal pressure using a fast burning powder and a slow burning powder even though the same pressure is attained. The fast burning powder "smacks" the bullet harder during a shorter time causing more obturation. The slower burning powder gives a gentler "shove" to the bullet and causes less obturation even though the pressures are the same.

Now let’s say we want 1500 fps with both a faster burning powder and a slower burning powder. The faster burning powder will smack the bullet harder and have a higher pressure to achieve the 1500 fps. The slower burning powder will push the bullet slower and with less pressure to achieve the 1500 fps. Bottom line; the faster powder causes more obturation than the slower burning powder given an equal velocity.

Now there is another very important consideration here. That is the consistency of ignition. If the powder doesn't ignite evenly and burn uniformly then accuracy will also suffer. Since you don't want to use a filler then powders must be chosen that provide uniformity of ignition. As I stated earlier; Bullseye and equally fast and easily ignited powders are good up through 1150-1200 fps with PB bullets. Unique and powders of equal burning rate and easy ignition qualities can take you from 1150 up through 1500 fps without the use of filler.

One question; exactly which PB cast bullet are you trying to get sub 3 moa accuracy at 1500 fps with?

Larry Gibson

[Marlin Junky]

Larry,

None of these PB loads I have tried in the .350 should have created any obturation. I have been shooting alloy hardnesses that are not supposed to obturate until 38.8K to 41.8K PSI. The whole thing is, why am I leading near the chamber with these BHN values while generating less than 24K PSI with bullets up to .0015"-.0020" over groove? The only thing I can come up with is there's a gas leak happening upon the initial engraving that wouldn't occur with a much softer bullet (say 15 to 16 BHN). The bullet in question is Lyman 358430 with all three grooves filled with LBT SOFT Blue. Also, the .359" bullets seated to the same COL as .3580-.3585" bullets rub against the throat slightly on the forward driving band; i.e., I think my sizing of about .3585" is just about optimum for this chamber.

BTW, put a gascheck on a similar weight bullet (SAECO 356) just a hair over groove diameter, with less bearing surface and use the same lube and the results are one hole groups at 75 yards (up to 10 rounds) at 1900 fps. Load specs are 26 grains WC-820 with 450F HT'd clip-on WW metal. The BHN is approx. 21 which is definitely above the hardness required to limit (or avoid, not sure which) obturation; i.e., 25.0K PSI/1440 = BHN 17.4.

Please don't even bring up powder ignition... every round I fire runs over the chronograph and I'm very particular about my chronograph stats.

MJ

[runfiverun]

m.j. you shoot p/b cast in your revolvers right?
i know that the 44 mag makes up to 40k and they shoot fine with ww's +2% or 1% tin right?
the major difference here is you are basically shooting a revolver round but with a huge case.
you might have to use a filler, just because, even if you are using a powder that is not position sensitive.
you might wanna look at something like aa 5744 or trailboss for this application.
a fluffy,goofy type of powder.

[Marlin Junky]

m.j. you shoot p/b cast in your revolvers right?
i know that the 44 mag makes up to 40k and they shoot fine with ww's +2% or 1% tin right?
the major difference here is you are basically shooting a revolver round but with a huge case.
you might have to use a filler, just because, even if you are using a powder that is not position sensitive.
you might wanna look at something like aa 5744 or trailboss for this application.
a fluffy,goofy type of powder.

runfiverun,

I haven't shot a revolver (which is a different animal) in years BUT, like 45-2.1 stated above..."The correct alloy for the intended purpose". BTW, for whatever reason, be it pressure or bullet friction, I was never able to do 1500 fps from a revolver without a gascheck. About 1200-1250 fps was all I could do accurately with a PB boolit but I've learned quite a bit since then.

MJ

[45 2.1]

Can you explain the mechanics behind "not the right alloy"? Is some obturation necessary when using PB bullets? This business of "obturation" is very missleading to everyone. Your alloy should be near the "yield" point for the alloy to be right. The mention of "tensile strength" is incorrect in the technical writings. If I understand the mechanics, then perhaps I can put QuickLoad's pressure data to good use when concocting handloads. Forget Quickload, the older Lyman manuals have a lot of good data to lead you as to a load that will do what you want. Accuracy with any cast boolit is a combination of things, correct alloy, load, boolit fit, lube, the way its put together etc. Following someone else or the crowd usually gets you no farther than that person or crowd participant. Choose wisely........

Not completely on the subject but nevertheless still a concern:
I don't want to use bullets that are so soft they are downsized when seating into case necks. If your boolits downsize, your case necks are to small....... Use a expander that is 0.001" smaller than boolit size, which may be quite a bit larger than what you've got. By comparing the diameters before and after seating (of a pulled bullet), I've noticed that necks on several types of cartridge cases (e.g., '06 and belted magnums) can downsize BHN 10-11 bullets when seating into the cases. I use a lot of 8 BHN boolits at higher velocities than you've stated and mine don't downsize at all, but I use an expander correct for the boolit size. I suppose the combination of a little harder bullet and maybe a little bigger custom made expander would probably cure this but I've already got a drawer full of Lyman M-dies so it's not like I'm using all the wrong tools! Are you sure, considering your not getting results?

[Bret4207]

I don't think Bhn is the be all/end all of this problem, or any problem for that matter. I'd listen to the advice given, play around with my Bhn (straight WW to start) and my sizing, especially my sizing. The other guys give the tech answers, I'll go to a more meta physical answer- you need to make the gun happy and match your load to it's wants. Keep looking. In the end it's possible that boolit my just be a stinker in your rifle. It happens.

[44man]

Obturate means "TO SEAL", not to expand. You do not obturate a boolit, you expand it to make it obturate.
Starting with an oversize boolit gives you obturation without a need to expand. In some cases you do not want the boolit base to expand at all to maintain it's integrity in an as cast condition.
But Larry says a lot of right things about the time/pressure curve. You need to spread it out so the peak is down the bore instead of punching the boolit while still in the brass.
You do not want the boolit to skid or as some say "strip" the rifling as it enters the barrel. You need to keep the rifling marks on the base of the boolit the same size as the rifling in the barrel.
That means a slower, more gentle powder and a hot but low pressure primer. Start the powder at the bottom, not all through the powder column.
You really need to watch powders with cast. I tried 4198 in my 45-70 and it works with jacketed but I got extreme pressure and velocity excursions with cast.
I tried 4227 and accuracy was totally gone.
I went to 4759 and it is working perfect with any weight or type boolit. I have taken my PB boolit to near 1800 fps without a problem but groups get larger over about 1650 fps in my gun.
Recovered boolits from the wrong powders showed very wide rifling marks the full length of the boolit, even those at 30 BHN.
The wrong powder also did the same to gas checked boolits, the check is not strong enough to prevent damage when the boolit is started too fast.
Turn the case into a rocket launcher instead of a firecracker!

[243winxb]

From Lyman-
While antimony is used to harden the bullet, the mixture of tin is critical, for while antimony mixes with lead in its molten state, it will not remain mixed when it solidifies. If tin were not added, we would have pure antimony crystals surrounded by pure lead. A bullet of this type , while it feels hard , would certainly lead the bore and eliminate all potential for accuracy. In a lead-tin-antimony mixture, the antimony crystals will be present just the same, but they will be imbedded in a lead-tin mixutre. As the bullet cools the tin will form around the antimony-lead keeping your bullets from leading the bore. Use #2 alloy. Air cool. Make sure the bullets do NOT obturate. Use 50/50 alox lube. Click photo for larger. http://i338.photobucket.com/albums/n420/joe1944usa/th_Alloy_20090610_1.jpg (http://i338.photobucket.com/albums/n420/joe1944usa/Alloy_20090610_1.jpg)

[TREERAT]

marlin junky; I am using a .358 win in a ruger frontier. when I started casting for this gun I was water dropping the plain base, thinking I needed harder, I could only go to 8g red dot or 10g unique before I got leading. each time I posted someone always said QUIT water dropping, well I finally listened. they were right!!! I can now push them hard with no leading, but at about 1500 fps accuracy goes away.

check out my post in the pp forum ( FIRST TIME: pp .358 win)

[44man]

From Lyman- Use #2 alloy. Air cool. Make sure the bullets do NOT obturate. Use 50/50 alox lube. Click photo for larger. http://i338.photobucket.com/albums/n420/joe1944usa/th_Alloy_20090610_1.jpg (http://i338.photobucket.com/albums/n420/joe1944usa/Alloy_20090610_1.jpg)
OH, OH, you did it! The boolit MUST obturate "SEAL" but it should NOT expand.
We need to say it correctly.
If you take a boolit and put it on the bench and hit it with a hammer, it "EXPANDS", it did not "OBTURATE."

[Larry Gibson]

Marlin Junky

None of these PB loads I have tried in the .350 should have created any obturation. I have been shooting alloy hardnesses that are not supposed to obturate until 38.8K to 41.8K PSI.

As mentioned in another post; "obturation" actually means to seal. Perhaps your bullets are not sized to fit the throat as well as you think. Also if your bullets are "sized down" during seating then you really need to address the neck expander as 45 2.1 mentions. If sized down then a lot of gas is working on the undersize part of the bullet before it enters the throat, especially on a harder alloy that does not obturate.

The whole thing is, why am I leading near the chamber with these BHN values while generating less than 24K PSI with bullets up to .0015"-.0020" over groove? The only thing I can come up with is there's a gas leak happening upon the initial engraving that wouldn't occur with a much softer bullet (say 15 to 16 BHN). The bullet in question is Lyman 358430 with all three grooves filled with LBT SOFT Blue. Also, the .359" bullets seated to the same COL as .3580-.3585" bullets rub against the throat slightly on the forward driving band; i.e., I think my sizing of about .3585" is just about optimum for this chamber.

BTW, put a gascheck on a similar weight bullet (SAECO 356) just a hair over groove diameter, with less bearing surface and use the same lube and the results are one hole groups at 75 yards (up to 10 rounds) at 1900 fps. Load specs are 26 grains WC-820 with 450F HT'd clip-on WW metal. The BHN is approx. 21 which is definitely above the hardness required to limit (or avoid, not sure which) obturation; i.e., 25.0K PSI/1440 = BHN 17.4.

If your case's neck tension does not size down PB bullets cast of WWs then cast some of that alloy and hand lube 10 of them with the LBT Blue soft and test them with the 820 load "as cast". I know you said you didn't want to discuss lube but since you/we are let me also suggest another 10 of the same "as cast" bullets cast of WWs only this time lube them with LLA. With that bullet I'd dab the grooves full with some on my finger instead of tumbling them. Load them over your 820 load and test also. The test is for accuracy and no leading in the throat. In the case of the GC'd bullet the harder GC expands the case neck and the cast bullet is not sized down by the case neck tension.

Please don't even bring up powder ignition... every round I fire runs over the chronograph and I'm very particular about my chronograph stats.

Let's eliminate the leading problem and then tackle the accuracy problem if then necessary. Uniform chronograph stats are no indication of how fast a time pressure curve is. A very fast powder like Bullseye can have very good "chronograph stats" and yet still have too fast of a time pressure curve. Conversly, your load of 820 may have very good "chronograph stats" and yet still be too slow of a time pressure curve. There is a balance of ignition and time pressure curve that must be met. In the case of PB bullets pushed to the max (1500+ fps) with very good accuracy the width of that balance band is narrow.

Let's eliminate the leading problem and then tackle the load and accuracy problem if then necessary

Larry Gibson

[TREERAT]

with your lyman 358430 pb, same bullet I started with in my .358 win ruger, if you will just try this I beleive you will learn many things an a light will suddenly come on, it sure did for me.

#1- size your 358430 to .360 diameter
#2- load the the bullet jamed against the lands
#3- make sure your cases are long enough for your chamber, do not trim to book, measure and trim to YOUR chamber!
#4- flair cases as large as possible and still chamber an empty case
#5- DO NOT crimp, leave the flare, you will see why when you try it!
start with 10g unique and work up, NO FILLERS!

[44man]

marlin junky; I am using a .358 win in a ruger frontier. when I started casting for this gun I was water dropping the plain base, thinking I needed harder, I could only go to 8g red dot or 10g unique before I got leading. each time I posted someone always said QUIT water dropping, well I finally listened. they were right!!! I can now push them hard with no leading, but at about 1500 fps accuracy goes away.

check out my post in the pp forum ( FIRST TIME: pp .358 win)
Picture what happens! Softer lead is in a putty form when slammed with tons of pressure. When it enters the rifling it is "flowing" and can expand to obturate in the rifling which is good to a point. Eventually, you exceed it's ability to seal and it skids farther down the bore where the lead stops "flowing" and is harder again. Now the rifling marks will not fill themselves and you have gas leakage.
Pressure has a larger effect then heat, the boolit will never get hot enough to melt but hot gas will cut the sides from it's pressure.
They are cutting steel with water jets. No heat needed.
The problem is when slammed with tons of pressure, you no longer have the boolit shape you started with. I do not like to swage my boolits when I shoot them. The only change I want to see on a recovered boolit are the rifling marks.

[44man]

with your lyman 358430 pb, same bullet I started with in my .358 win ruger, if you will just try this I beleive you will learn many things an a light will suddenly come on, it sure did for me.

#1- size your 358430 to .360 diameter
#2- load the the bullet jamed against the lands
#3- make sure your cases are long enough for your chamber, do not trim to book, measure and trim to YOUR chamber!
#4- flair cases as large as possible and still chamber an empty case
#5- DO NOT crimp, leave the flare, you will see why when you try it!
start with 10g unique and work up, NO FILLERS!
Exactly what I do with my 45-70 rifle. I leave the flare to center the case. Unless using BP for the boolit to stop against, you need just enough case tension to prevent boolit movement. If using a magazine or tube, then you need to change things.

[Junior1942]

Size & lube a few bullets like normal, then give them a coat of Lee Liquid Alox. I'm betting your groups and leading will both shrink drastically.

[243winxb]

OH, OH, you did it! The boolit MUST obturate "SEAL" but it should NOT expand.
We need to say it correctly.
If you take a boolit and put it on the bench and hit it with a hammer, it "EXPANDS", it did not "OBTURATE." The bullet takes the rifling in a process called swaging when it is .001" to .002" over groove diameter, just like a jacketed bullet. If a bullet obturates, it is deformed in some manor and is to be avoided. simply following "Lee's" instruction works in most cases. IMR 4895 would be my powder of choice here.

[243winxb]

150gr or 195gr in the Lyman #358430? If using the shorter 150gr, there might be gas cutting. The nose of the bullet(bearing surface) must seal the bore before the base of the bullet exits the case mouth to avoid gas cutting. All depends on how you chambers leade is throated into the rifling.

[44man]

The bullet takes the rifling in a process called swaging when it is .001" to .002" over groove diameter, just like a jacketed bullet. If a bullet obturates, it is deformed in some manor and is to be avoided. simply following Lymans instruction works in most cases. IMR 4895 would be my powder of choice here.
Swaging into the rifling or expanding a too small boolit or an under size hollow base one into the rifling will make it obturate. If Lyman is using the word to describe deforming a boolit, they are wrong.
If a boolit does NOT obturate, gas will blow past it.
Different meanings.
Obturate = seal.
Expand = deform. Include setback (slump) here with expand.
Swage = obturate if the boolit is larger then the bore.
Hard, under size boolits will not obturate unless deformed or slumped by pressure.
Soft, under size boolits CAN obturate until pressure is too high and they skid, then they do NOT obturate. Either way, the boolit is damaged.
Soft boolits of the right size will obturate until pressure gets too high and they skid too far. Even slump will not help here.
Soft boolits OF THE RIGHT FIT shoot great if started gently.
Hard boolits can stand a higher starting pressure.
Hard gas check boolits can take even higher starting pressure.
But there is nothing wrong with starting a hard, gas check boolit gently, in fact it will increase accuracy.
On the average, the faster a given case reaches max pressure from a fast powder, the harder the boolit needs to be.
If you shoot a bullet in the 45-70, say, with a moderate load of 3031 and it shoots great, why go to Unique, Red Dot, 4227 or God forbid, Bullseye with cast? That is the opposite of what you want!
In fact, go to Varget in the 45-70 with cast. Go to BP and you can shoot pure lead! :Fire:
Who in the world said you need fast powder with cast? :confused: Is it to save money?

[Marlin Junky]

When shooting a bullet .0015"-.0020" (measured around the bullet's circumference) over groove diameter, that slightly rubs the throat all the way around on its forward driving band and while using an alloy way too hard for obturation to occur, where does the gas leak occur? Along the land/groove junction; i.e., in the corners? Or, is the pressure great enough (even at a measly 15K PSI... and it's not 15K until the bullet is 1/3 the way down the barrel!) that the lead alloy/steel seal is broken all the way around the bullet? The latter situation isn't very intuitive especially for a bullet approx. .0015" over groove diameter that's snugged up tight into the throat just before the primer's lit.

Here's another question: Since obturation is caused by pressure on the base of the bullet, how can we be guaranteed the base will be square when leaving the muzzle? This is why I'm wondering if the threshold of obturation isn't the point where our best accuracy occurs.

MJ

P.S. If I could catch these bullets (200 grains in my alloy) by shooting them into a big tank of water, maybe I could acquire some evidence explaining the gas leaking action; i.e., where along the bullet's shank it is taking place. When my neighbor goes on vacation this summer, maybe I'll borrow his swimming pool. [smilie=1:

[felix]

You can only get a flat exit base if the gun is concentric and the ignition keeps the boolit centered before it obturates. Tough to do without a tight neck situation which keeps the boolit straight on for its entire length through the leade. You can help matters considerably with faster ignition, but then you can over pressurise the boolit base. Therefore, there is a load with enough patience with any boolit, with any gun within reason. ... felix

[Larry Gibson]

Marlin Junky

When shooting a bullet .0015"-.0020" (measured around the bullet's circumference) over groove diameter, that slightly rubs the throat all the way around on its forward driving band and while using an alloy way too hard for obturation to occur, where does the gas leak occur? Along the land/groove junction; i.e., in the corners? Or, is the pressure great enough (even at a measly 15K PSI... and it's not 15K until the bullet is 1/3 the way down the barrel!) that the lead alloy/steel seal is broken all the way around the bullet? The latter situation isn't very intuitive especially for a bullet approx. .0015" over groove diameter that's snugged up tight into the throat just before the primer's lit.

Leading in the throat isn't only caused by gas leakage/cutting. It is also caused by and inadequate lube for the job. While I've not used LBT Blue Soft at that low of velocity it may just not be doing the trick. Try the LLA and find out.

Here's another question: Since obturation is caused by pressure on the base of the bullet, how can we be guaranteed the base will be square when leaving the muzzle?

Inaccuracy with such cast bullet loads is a good indication that the base isn't flat on exit. What you have to do is slow the time pressure curve down. Get the bullet moving slower and there is less obturation (damage) even if the velocity or pressure are the same. Didn't you read my "door" explanation of this?

This is why I'm wondering if the threshold of obturation isn't the point where our best accuracy occurs.

You can look at it that way or you can slow down the obturation and the damage to the bullet caused from it and achieve accuracy at a higher velocity.

MJ

P.S. If I could catch these bullets (200 grains in my alloy) by shooting them into a big tank of water, maybe I could acquire some evidence explaining the gas leaking action; i.e., where along the bullet's shank it is taking place. When my neighbor goes on vacation this summer, maybe I'll borrow his swimming pool. [smilie=1:

Heard of a guy who tested some bullets shooting strait down into the water. Cracked the bottom of the pool.....pretty expensive test! Again, the leading probably is not from gas leakage but from the lube. Try the LLA.

Larry Gibson

[44man]

When shooting a bullet .0015"-.0020" (measured around the bullet's circumference) over groove diameter, that slightly rubs the throat all the way around on its forward driving band and while using an alloy way too hard for obturation to occur, where does the gas leak occur? Along the land/groove junction; i.e., in the corners? Or, is the pressure great enough (even at a measly 15K PSI... and it's not 15K until the bullet is 1/3 the way down the barrel!) that the lead alloy/steel seal is broken all the way around the bullet? The latter situation isn't very intuitive especially for a bullet approx. .0015" over groove diameter that's snugged up tight into the throat just before the primer's lit.

Here's another question: Since obturation is caused by pressure on the base of the bullet, how can we be guaranteed the base will be square when leaving the muzzle? This is why I'm wondering if the threshold of obturation isn't the point where our best accuracy occurs.

MJ

P.S. If I could catch these bullets (200 grains in my alloy) by shooting them into a big tank of water, maybe I could acquire some evidence explaining the gas leaking action; i.e., where along the bullet's shank it is taking place. When my neighbor goes on vacation this summer, maybe I'll borrow his swimming pool. [smilie=1:
I hate to beat on you but you are still confusing expansion and boolit damage with obturation.
Obturation is NOT caused by pressure on the base of a boolit if the boolit is a good fit or oversize to the bore.
Once a boolit takes the rifling without skidding past the base and is spinning while pressure builds it will be fine all the way out. It will not suddenly strip the rifling at pressure peak somewhere down the barrel. This is where you lose it! :!: As long as the boolit is engaged and spinning it will just speed up and spin faster as pressure builds and it does not matter how far down the bore that occurs or even if the boolit leaves the barrel before the powder is done burning.
The major problem occurs at the time the boolit enters the rifling. THAT is where you need a seal---OBTURATION, SEAL, SEAL, SEAL, how much can it be explained?
THAT is where gas leakage starts, NOT down the bore but it will continue because OBTURATION is lost.
Start a boolit nose in the rifling gently, put a rod on the base and smack it with a 20# sledge as hard as you can swing it. What will you have????
Now do the same but add pressure slowly by putting weight on the rod until the boolit moves into the rifling.
Can you even picture the difference?

[44mag1]

I just learned more about cast bullets in this thread than I have in the last 2 years of study, Thanks

[Bret4207]

As 44mag1 says, good thread.

MJ- beyond the obturation/seal/lube issue- is it possible you have a loose spot or rough spot in your barrel? I don't know what Rugers barrels are like these days, but there was a time they were none too hot.

You say the forward band in large enough to rub the throat, what is the nose doing? Is it contacting the lands at all?

[Marlin Junky]

As 44mag1 says, good thread.

MJ- beyond the obturation/seal/lube issue- is it possible you have a loose spot or rough spot in your barrel? I don't know what Rugers barrels are like these days, but there was a time they were none too hot.

You say the forward band in large enough to rub the throat, what is the nose doing? Is it contacting the lands at all?

Bret,

Barrel's been fire lapped with a Tubb's kit and it shoots GC bullets very well to 2000 fps. It provides a smooth, consistent feel when cleaning with a tight patch too. It's definitely not a HV gun due to the fast twist and 6 relatively shallow grooves.

I'm going to try to repeat the whole experiment next week with bullets from the same batch drawn back to "match" the pressure. I was fiddling around with annealing last night and I may have gone a bit too far. 300F for 20 minutes yielded about 12.5-13 BHN which I think is too soft for 14.4 grains of Scot 453 in the .350. I think I need to be right around 15-16 BHN. I'll try 275F for 20 minutes tonight and see what I get.

MJ

P.S. One thing I should probably mentioned is that upon inspecting my brass, I've noticed traces of alloy from the shoulder/neck junction to the mouth.

[Marlin Junky]

You say the forward band in large enough to rub the throat, what is the nose doing? Is it contacting the lands at all?

Are you familiar with 358430? I picked this design because it's mostly bearing surface with a rounded point. It's kind of like a round SWC which doesn't touch the top of the lands forward of the leading driving band (IIRC, it measures about .346" on the very short nose section). There was a group buy here not to long ago so maybe if you do a search, you can locate some pics. My mold is a Lyman (in case there are some differences) because I like ferrous molds.

MJ

[Doc Highwall]

Take a look at Richard Lees article in his 2nd reloading manual about hardness and loading to 90% of the compressive strength of the alloy to prevent distorting the base of the boolit. I have been using this in my loads and it made me a believer.

[badgeredd]

I believe that this is the first thread I've seen that really gave a good description of obturation vs. upset/"damage"/expansion. Thank you guys. It helped me to understand the theory of the plain base boolit loading.

BTW, I shoot a modified 311291 in a SKS that is plain based without leading and decent accuracy (< 2 MOA) at 1500-1600 fps (depending on powder. Alloy is running approximately 16 BHN.

Edd

[runfiverun]

m.j.
take a real close look at how long your cases are compared to how long the end of your chambers neck area is.
if your cases are short and well it creates an area for gas and boolit base to collide this could well explain the lead blown back on your case neck shoulder area especially if you are getting some lube there too.

[Bret4207]

Are you familiar with 358430? I picked this design because it's mostly bearing surface with a rounded point. It's kind of like a round SWC which doesn't touch the top of the lands forward of the leading driving band (IIRC, it measures about .346" on the very short nose section). There was a group buy here not to long ago so maybe if you do a search, you can locate some pics. My mold is a Lyman (in case there are some differences) because I like ferrous molds.

MJ

Yup, got one. Is the nose section supported at all? It may have nothing to do with it. Sounds to me like you;re making the right moves, I just wouldn't discount the softer alloys. It might work.

[TREERAT]

(m.j.
take a real close look at how long your cases are compared to how long the end of your chambers neck area is.
if your cases are short and well it creates an area for gas and boolit base to collide this could well explain the lead blown back on your case neck shoulder area especially if you are getting some lube there too.)

this is what I tryed to tell you, but runfiverun said it better!!!
TRIM TO YOUR MAX CHAMBER LENGTH, not what some load book says. and leave the flare, do not crimp. and I bet it solves your problem!

[Frank]

I just learned more about cast bullets in this thread than I have in the last 2 years of study, Thanks

Yeah, 44man is pretty good. I don't waste my time. I go right to the source. :coffee: