bullet bases

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Ross Smith posted this 10 December 2019

After reading a little by Dr. Mann and Harry Pope about bullet bases it brought back some of my worries about bullet bases. Not just Pope and Mann, but several experts have stated the bullets base to be the most important part. They were even arguing that the small amount of lead displaced by the lands causing small fins on the edge of the bullets base to alter the point of impact. Now these guys were probably concerned about .01" or less which is enough to win some matches. But how does that effect us mortals?

I've often wondered about gas checks that don't go on straight. Not just the really ugly ones but also the ones you need a small square to see the the bullet tip when stood on its base. While I was lube sizing several hundred noe 165gr fp bullets and not really trying for match quality bullets , I was getting quite a few crooked gas checks, some would not even stay on the bullet. So the light bulb flashed on. I sorted out 10 really bad ones, the ones you recycle into the pot. Some of these would not even stand up. Very crooked. Then I got out my small machinist square and sorted thru the bullets to come up with 10 that were very square to the world. These 2 groups were loaded over 20 gr R7(my load my fingers) in 30-06 mixed headstamp cases. I also took 10 30-06 cases loaded the same but with noe xcb bullets, my normal load. The xcb were my control and the other 2 groups were the experiment. The xcb went inot 2" out of a cold barrel. ED's red wiped thru the barrel then shot my 10 good 30-30 fn bullets. 4". I didn't expect much and was actually pleased with 4", after all no load developement. Next came the really bad bullets, 4". No effect, at leasdt in this under funded experiment. So ther goes my excuse for those wild fliers that miss the whole target.

What say you all?

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Tom G posted this 11 December 2019

Ross, 

Out of square bullet base will definitely cause fliers. But not fliers that will miss the target. About 6 or 8 yrs. ago I decided to find a good cast bullet load that would shoot in my AR-15 house and bug-out gun. I shot hard water dropped bullets and had a load that shot an average of 1.25" at a hundred yards.  I tested it against a load made up of jacketed FMJ bullet that were just blasting quality and fairly cheap. The cast load beat out the jacketed load. by a small amount. 

Later, my brother decided to work up a cast load for his AR and eventually sent me some bullets he had cast and shot in his gun. I shot them in my gun and got unexplained fliers. They maybe doubled or tripled the group size. They were in the range of 4 inch groups.  I got to looking at his bullets and when sitting them up on their bases, I could see the gas checks were  on slightly crooked. They definitely caused fliers.  

Perhaps your groups are so large at 4" that the fliers don't make them any larger than the groups without fliers. Maybe if you worked up a load that was accurate, you would see the difference. Following Dr, Mann's lead, you might try taking the crooked gas check bullets and orienting them in the chamber so that the out of squareness was in the same direction for all the bullets. Maybe they would shoot to a group!! Seems to me that Mann did the same type test with plain base bullets.   

When I was shooting CBA benchrest, I always bumped my bullets in a bump press. This was for two reasons. First to make the bullet the exact same shape as the tapered chamber throat in the gun and make the rear driving band a couple of tenths larger so I would have slight interferance fit when I chambered them. This also formed the gas check flat and square on the bullet. Having a friend who was a tool and die maker, I had him take a couple to work with him and measure the base squareness on an optical comparator. He reported back that the samples that I had bumped were "dead nuts Square". These bullets would routinely shoot around  a half inch at 2500 fps. Knowing that the edge of the gas check was a critical factor to accuracy, I bumped them just hard enough to flatten the base but not remove the round edge of the gas check. These were tapered bullets seated into a tapered throat. 

My bump press was adjustable for the amount of bump and had an ejector built into it. The bump die was made from the same throater reamer that I used to throat the chamber throat in the gun. I purposely designed the throater to make a .309 throat diameter into a half degree per side taper on the lands. Thus the bullet fit the throat like a morse taper. It also sealed in the back end to stop any gas from flowing past the bullet and damaging the bullet or knocking the lube off the bullet. Bumped bullets were .3093" into a .3090" throat. and were seated way long with just the base of the bullet in the case neck. This allowed the bullets to be oriented straight to the rifling because the chamber throat held the bullet straight and hot the case neck. 

One of my deceased prairie dog shooting buddies was a retired scientific type. His I Q was measured over 165. At one time he worked on and off a bunch of government projects. One was to develop a nuculear artilliary shell. The shell had a nuclear warhead and had a rocket motor attached to the base of the projectile. The rocket motor was timed to fire off near the top of the trajectory curve and propel it about 5 times further than normal. This shell had serious accuracy problems. As a result they determined that the edge of the base of the shell was being eroded by the rocket blast. The fix was to implant a ceramic ring to form the edge of the base of the bullet and hold up to the heat generated by the rocket blast. It shot accurately when they did that. 

Tom G. 

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Squid Boy posted this 11 December 2019

I use a lot of M198 duplex ammo and even some experimental quad bullet stuff while in the Army. Both had angles built into the last bullet in the stack. I believe the angle was 4% and it opened that last bullet so as to hit about 10 inches off center. It seemed like a good idea but the individual bullets were pretty light and easily deflected. I would say your results are unusual and there could be other factors at play. My experience is the better the base, the better the shooting. Thanks, Squid Boy

"Squid Pro Quo"

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Ross Smith posted this 11 December 2019

I agree and like  the posts. I purposely made sure that I was not trying for "match" ammo. Just wanted run of the mill plinker stuff and I will see if I can refine this load for my '03. It doesn't like the xcb but did shoot "ok" with the flat nose. The other thing being that the flat nose mould is a 4 chamber mold and can spit out a lot of bullets. From now on for my plinkers I won't worry about sorta off kilter gc's but the ugly ones will still go back in the pot. 

If I remember right it was Mann or someone like him that said the gap in front of the gc collected the displaced lead and increased accurracy over pb's. However the pb breach seaters sure do shoot small groups. Which brings me back to long slow bullets in slow twist barrels........my other bug-a-boo....rifling twist rate.

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John Alexander posted this 11 December 2019

Ross asks -- "What say you all?

I say congratulations on running a nifty, although limed, experiment challenging one of the hoary old cast bullet axioms that most cast bullets shooters swallow whole with never a doubt.  Being skeptical is the only way we will ever learn anything.

You found that even with horrendously crooked bases (some wouldn't stand on their bases) the groups were the same as the bullets with good bases.  This isn't what we have been told to expect. True, the test was small and the results doesn't say much about what the results would have been if the perfect bases had shot much smaller groups.  I assume you were shooting at 100 yards and that level of accuracy, or larger, is often mentioned in TFS articles and not unreasonable for many uses. 

I have run a lot of comparison test between "perfect" base bullets and bullet with base defects and have been surprised at the lack of dramatic accuracy loss easily seen defects or slightly skewed based cause. 

So far I have not been able to show that gas checked bullets with rounded bases or small wrinkles in the base reduce accuracy at all in five shot groups that average 1" 

I have also found bases skewed up to 2 degrees (easily seen) increased my groups from average of .96" to 1.28".  1.28" not good to win many CBA matches but still good enough for any practical use. This test was written up in Fouling Shot 212, July/August 2011. I would be happy to send a copy to anybody curious enough to send me their email address.

Keep on experimenting Ross.

John

 

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RicinYakima posted this 11 December 2019

John wrote; "I have also found bases skewed up to 2 degrees (easily seen) increased my groups from average of .96" to 1.28".  1.28" not good to win many CBA matches but still good enough for any practical use."

And that is the crux of the issue, for me. When I am prepping for a 120 round match I make about 200 bullets. When all finished the VISUAL best 120 go into the match boxes, but the others are foulers (well barrel warmers) and sighters. Foulers go into the dirt, but the sighters will almost always go into the group so are used for sight changes.

Making bullets for the 30/40 for walks in the sage brush to shoot varmints, vermin and rock buffaloes, don't get much of an inspection, because it is hit or miss. Part of the adventure is having bullets I made myself to shoot, but another is making the "best" that it is possible to make. John has convinced me that much of the OCD things I do for match bullets is just to make me feel good, and is seldom seen on the targets.

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BigMan54 posted this 12 December 2019

Before the Saeco Lubi-Sizer with swing out gas check seater. And the Lyman attachment for their's and RCBS.

My Dad used a "coin slug" over the top of the size die to seat gas Checks on straight. 

Don't need the slug these days but I've always seated my gaschecks on straight with the gascheck seater.

If the straight on gaschecks worked for Dad, that's good enough for me. 

And It's proved itself to me shot after shot. 

I REALLY HATE AUTO-CORRECT 

 

Long time Caster/Reloader, Getting back into it after almost 10yrs. Life Member NRA 40+yrs, Life S.A.S.S. #375. Does this mean a description of me as a fumble-fingered knuckle-draggin' baboon. I also drool in my sleep. I firmly believe that true happiness is a warm gun. Did I mention how much I HATE auto-correct on this blasted tablet.

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Squid Boy posted this 12 December 2019

I think one of the more interesting aspects of Mann's tests was that purposely damaged bullets shot well when oriented to exit the muzzle in the same position on every shot. That is, bullets with the same obliqueness or off balance condition shot well. Mixed problems produced fliers regardless of orientation. I find in my own testing that once you get down to very small groups, everything makes a difference down to what seems like an immaterial thing when striving for the absolute minimum group size. You will occasionally shoot a fantastic group with mediocre bullets due to a happy coincidence but it won't happen often. Kicking new ideas around and challenging the old ones is what makes cast bullets so interesting to me and I am a new comer to this. My humble opinion only. Thanks, Squid 

"Squid Pro Quo"

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Dale53 posted this 12 December 2019

Due to vision problems, I no longer compete in cast bullet matches. However, since it is relatively easy to produce near perfect bullets, why would I want to cast imperfect ones? When using gas checks, I simply used a gas check seater to make sure they were seated perfectly. Easy-peasy!

These comments can be taken as confrontational. That is not intended at all. What I would like to do is to simply encourage anyone who is casting bullets to set high standards for themselves, and often with a change in attitude, comes near perfection!

The act of positive thinking...

FWIW

Dale53

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Ken Campbell Iowa posted this 12 December 2019

about " square " bases ...  back when i was trying to get my sporter rifles under 2 moa with cast, ..... having tortured my way through Mann's book a couple times ...  and read a few articles on Pope and even got to,play with a Pope 32-40 muzzle starter system ( with Pope mold )  , remembering the trouble he took to have a fitted bullet and his comments on bases ...

having determined that the first rule ( bullet snug in the throat ) was to be obeyed first thing ...

i fantasized that the base was the magic key to the last 1 moa ... so i dedicated ~800 rounds of pretty good castings with and without lathe collet turning the bases .. the idea was that would be the only difference in fit and basic form ..... Joeb is right,  ::  800 ain't enough cool ... but there was a strong hint that better bases shoot better ...  normalized bases gave me the only 10 shot groups under 1 moa with sporter rifles.   but the magic trick failed to turn my pretty good castings into under-1.5 moa consistently ...   btw, i used commercial all Taracorp Magnum alloy, not hardened.  great stuff.

interesting that half the bases were turned 90 degrees flat ... and half were turned with a large bevel base ... both shot the same ...   yes, all used the old lyman checks ... even the bevel based ones ... you would think those would distort unevenly and groups would enlarge... but they didn't seem to be worse.

also through those guns with the same starter castings, i made several swagers ... mainly to square the base y checks ..  and they also showed slight improvement .. but of course the whole bullet was re-formed during the swaging, so several variables were changed.

the above was through factory sporter barrels, even 2 moa  cast groups required some load development, and a bit of luck.   those factory sporters would shoot under 1 moa with mj bullets.

and yes lathe turning bases is tedious ... but you can try different cuts on different bullets.   the squisher tool is a better answer once you determine what works. 

*************

so today for my plinking level loads, i cast scrap, obey rule 1 ( snug in the throat ) and visibly check and remelt any terrible base castings ... the nose is much less critical   ...  no gas check and about 1100-1300 fps... i expect a max of 3 moa for plinking and can usually get there ... eventually . 

if i were shooting group competition, i would definitely normalize the bases.

ken

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Ross Smith posted this 12 December 2019

Next I'm gonna load up some of the wrinkled pitted ugly poured to cold dirty mold bullets. Of course I'll use 10 just so I have a statistical sample.

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max503 posted this 13 December 2019

I've often wondered if the pressure of firing would seat a crooked gas check.

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RicinYakima posted this 13 December 2019

max503, me too. I would think it would an Ideal slip on, but wonder about crimp on ones?

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45 2.1 posted this 13 December 2019

I've often wondered if the pressure of firing would seat a crooked gas check.
Indeed it does. Tests involving intentionally crooked seated Hornady gas checks show a raised portion of lead above the gas check on the part that isn't fully seated on the bullet shank. All recovered bullets in the tests showed this and all gas checks were flat on the bullet base.

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John Alexander posted this 13 December 2019

Ric,

Remember that Dan Lynch showed either in a Fouling Shot article or in a post to the forum that the thickened rim in advertisement for Hornady gas checks doesn't exist on his sectioned gas check.  So maybe it doesn't crimp as solidly and thus 45 2.1,s observations.

This may be the reason why the skewed gas checks shoot better than they outa.

John

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RicinYakima posted this 13 December 2019

John, After I saw that, I looked a lot of about 10 Hornady .30 gas checks. They are not like the illustrations, but appear to be the sheared metal from the punching process. But I have no guess as to how strong they would be. I am glad 45 2.1 added his experience on this topic. Ric

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45 2.1 posted this 13 December 2019

.  So maybe it doesn't crimp as solidly and thus 45 2.1,s observations.
Once ran thru the sizer in a tilted condition, those Hornady checks take excessive force to move using the lubrisizer. Try taking one off and it's a job. The starting force from the primer is about 2,000 PSI and it does move a tilted GC... of course you usually have to knock the bullet out of the rifling to see that. In all my testing it seems the GC is seated flat before it reaches the rifling.

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Ross Smith posted this 13 December 2019

HMMMMMMMMMMMMM

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Tom Acheson posted this 13 December 2019

Unless I missed it, this discussion is focused on bullets that will eventually have gas checks applied to them.

The guys who shoot Black Powder Cartridge Rifles, typically use single cavity molds for large—dia. and weight—-bullets. These are plain base bullets, the match rules exclude the use of gas checks. The first step of bullet quality evaluation is squareness of the base. You can see it after swinging the spruce plate over and before you open the mold halves. Mold fill-out can be immediately seen. If there is any “roundness” to the edge of the base, the bullet is rejected. 

Has there been extensive testing to explore the benefits of square vs. unsquare plain base bullets? Maybe but so far I’ve not seen reports of this kind.

Admiitedly the muzzle velocity of these rounds are quite a bit slower than the benchrest match loads being discussed here.

It would be interesting to see what the CBA match shooters in the PBB (Plain Base Bullet) Gun category/class think about the need for absolute square bases. Since they cannot use gas checks, they need to limit their muzzle velocity. Is an absolutely square base a must for accuracy?

Tom Gray got me hooked on the use of a bump die/press (back in 1997) and everything I’ve loaded over the years since for CBA match use, has been cycled through a bump die. I agree with the benefits of bumping that Tom outlines here.

Tom

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BudHyett posted this 13 December 2019

Tom Acheson's question concerning Plain Base Bullets has intrigued me for the last decade, Visual check out of the mold for base sharpness. weigh, then lubricate gently in a .320 die to assure there is no oversize band or slump in the body. Then select the bullets that simply look good. 

With the breech seat tool, in theory the tool pushes the bullet base square if the tool is a tight fit in the chamber. Any slight irregularities in the soft bullet body will be pushed straight into the leade and the bullet will start as true as possible.

I have a new tool shed coming for casting and reloading in the next week. Adding shelving and electricity, then moving in will take through Christmas. A structured test for both the .32-20 CPA and the .25-20 WCF barrels to prepare for next year's competition. The testing will include powder choice, powder charge, lubricant choice and Pb/Sn ratios. Once these are established, then work on the questions of base alignment and seating depth. 

Tex Johnston, the Boeing pilot who barrel rolled the new 707 at Sea Fair without anyone knowing he was going to do this said, "One test is worth a thousand expert opinions.”

Farm boy from Western Illinois, living in the Magical Pacific Northwest

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Shopdog posted this 14 December 2019

It only matters,if it matters.

If the load and rig are in tune,and you have better than average,very clean bases, along with a good "driver" you may not see much gain in obsessing over it. But go outside "normal" for cast boundaries and it can turn a load around. I mill bases on a BP in fixturing that does 5 bullets at a time,in.... and with less effort than it takes to write this post. Again,depending on the rig/load/tune.... it can turn a 1 moa load into bugholes. My work is centered around killing varmints. 3 and 5 shot,DAILY.....rain or shine ragged hole groups at starting JB velocity is what I not only strive for but,honestly is what it takes in the field if you really want to "get after it". I'm not into reans of statistical data which is why I don't post more. Good luck with your project.

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