Success in trapping boolits to read the rifling- thanks to Jane Fonda

[oldandslow]

Casters, 6/20/13

I've been having fits trying to figure out why my 30-06 boolits keyhole (AccurateMold 31-180grain-F(gas checked). The bases are perfect, I weigh them into 0.1grain groups, size and gas check them in a Lyman or Lee push through sizer, and ice-water drop them to a BHN of 21. The bore was slugged and the boolits are sized about 0.0015" oversize and seated 0.010" off the lands. There is no leading. At speeds over 2000 ft/sec they become unstable and keyhole. I run the same boolit in my 30-30 at 1700 ft/sec with no problems.

So I wanted to recover the fired boolits to check the rifling and gas checks. I tried a 3.5 foot water column inside a 3 inch heavy walled pipe with a plate welded on the far end. The boolits were recoverable but I got doused with four gallons of water every time I fired a shot. The rifle also ended up soaked.

There were many helpful suggestions from you fellow casters in my other thread. Some helpful suggestions which didn't work out were shooting into a snow bank (I live in the tropics), shooting into someone's swimming pool, shooting wet phone books (can't find any now with the internet being so prominent), and oiled sawdust. What I do have is a Salvation Army store by me with a lot of second hand books for $0.50 each. The first one I picked out was Jane Fonda's book "My life my way." Fifty cents was still over priced for her book but it was really thick and should slow down boolits well. I picked up about twenty books, soaked them in water in square buckets for 48 hours (they swell up about twice the original size) and shot away. The 30-30 boolits went in 19 inches and had good, sharp rifling but the gas check fell off. The 30-06 boolits were tumbling at entry into the books (10 feet from muzzle to books) and the nose broke off each boolit (velocity 2200 ft/sec). The boolit base with two driving bands tumbled about 18-19 inches into the wet books, the nose broke into little pieces. The gas checks also fell off. The rifling was indistinct on the bases.

So I'm thinking that to stop the 30-06 boolit instability I either need to slow down the velocity or increase the hardness (without getting too brittle). The RPM of each boolit is 102,000 for the 30-30 (1:12 twist), the 30-06 is 159,000 with a 1:10 twist. Is my thinking right?

thanks- oldandslow

[Ben]

oldandslow

(velocity 2200 ft/sec)

My first thoughts are to slow things down.
Try that bullet with 16.5 grs. 2400 in your 30-06.

[oldandslow]

Casters,

The only powder I can get out here in the middle of the Pacific is 4064 and 3031. I've been using 4064 initially with 40 grains. I've used more powder up to 44 grains and the faster the velocity the more the tumble. I've even dropped the powder load to less than recommended (as low as 34 grains) and get fewer tumblers but still running 30-50% tumblers and keyholes. I've tried separating and shooting the individual mold cavity boolits to see if there is a mold problem but no luck. Boolits from each cavity tumbled with equal frequency.

I've ordered and received some Superhard alloy (30% antimony, 70% lead)from Rotometals and am considering increasing my antimony alloy content to 10% (presently assumed about 4% for wheel weights) and water dropping to see if I can eliminate the tumblers and then test with my Jane Fonda book to make sure it doesn't fracture by being too brittle.

thanks- oldandslow

[303Guy]

Perhaps your boolits are too hard. Perhaps it's not the hardness but too much stress on the rifling driving faces resulting in rifling skid. Maybe it's both. I've had rifling cutting half way through the broad land impressions of the Brit with a smooth sided boolit with a full length bearing surface. A GG boolit will have far less rifling engaging area so skidding could be quite possible.

I'd suggest a way slower powder and a filler that forms a wad under the boolit. The idea is to accelerate the boolit gently and to assist the rifling with the wad as well as to seal the bore. Wheat bran has been used successfully to overcome accuracy problems and is probably what I'd start with were it me. Wheat bran filler helps raise the pressure of a slow powder to burn it fully but that's probably not what you need unless the slow powder is going to produce too high a velocity in which case less powder with wheat bran filling the case (it should be lightly compressed on top of the power by the seated boolit). I'd also suggest less antimony and some tin and for toughness you could consider adding copper. See the copper alloy threads under lead and alloys. Try balancing the antimony with tin, i.e. equal amounts of each or at least reduce the antimony and add some tin.

[Larry Gibson]

Bullets are probably too hard and you are driving them too fast for the alloy and fit.

If you are presently using COWWs you there is probably less than 4% antimony in the them....that is good. There is probably less than .05% tin in them....that is bad. Add 2% tin to your COWWs and let the cast bullets AC for 7 - 10 days before sizing, lubing, GCing or loading.

Increasing the antimony content will only make the problem worse. What you want is a balanced ternary (3 part) alloy made of of lead, antimony and tin where the antimony and tin are balanced in proportion to make the antimony go into solution with the lead. Right now that isn't happening and the fact that the noses break off indicate the alloy is already too brittle.

The RPM of each boolit is 102,000 for the 30-30 (1:12 twist), the 30-06 is 159,000 with a 1:10 twist. Pushing that bullet above the RPM threshold obviously takes it's toll. Soften up and balance out the antimony/tin content of the alloy and slow it down.

I suggest you drop back to 28 gr of 4064, use a 3/4 gr dacron filler and work up to 34 gr.

Larry Gibson

[runfiverun]

i'd suggest you re-measure the rifle.
about 3"s in the muzzle and about 3"s in the chamber end.
and another down the barrel.
look and feel for inconsistences.

i'd then try a regular air cooled boolit with 26 grs of the 30-31 and a tuft of filler.
this will give you a good velocity that isn't too fast or too slow.

[popper]

I shoot Tom's 165 version of that CB, 2% Sb, AC or WD in 308, >2200, 1:10. No problems at all. Yours is 0.1" longer, shouldn't be a twist problem. Tumbling @10' indicates a stripping problem to me. Broke at the crimp groove? GC falling off? Reslug it as R5R suggests. Sure it is not casting/dropping/sizing/crimping problem?

[Iron Mike Golf]

What checks are you using?

[tomme boy]

Too hard! balance the alloy as the others have said. What is the 3006?? Has it ever had factory sights on the barrel? I had a Rem 700 that had regular sights on it in 223. The front sight was not installed right. You could see right where the screw was that held the sight on looking into the barrel. It was a dimple. I cut 2"s off the barrel and put the sight back on myself and it fixed the accuracy problems I was having.

Something to look for????

How many rounds have been shot thru this? You might have a really worn throat.

[1500FPS]

The notion that the alloy is too hard plum sounds loco to me. Isn't using a harder alloy what many tell one to use to get higher velocity with it's associated higher pressures? Wasn't this the whole idea about Badger Edd's copper alloy? To make a harder tougher bullet? Although I don't shoot real high velocities 2000 fps or little over that is not unrealistic in a 30-06. I'd love for someone to show me a cast bullet that they have stripped in a rifle. I'm not talking about gas cutting, I'm talking about stripped to the degree that it had the lands shave the bullet down and it did not spin at all going down the bore. In my opinion that cannot be done. The worse slipping, and that is not stripping to me, is in revolvers and happen because of the bullet jump to the forcing cone and barrel.

Tell us what gas checks you are using. I particularly liked runfiverun's post. Find out if you are sizing for the diameters that may be encounted in the entire length of the barrel. If there is a tight spot, particularly before the muzzle, your bullet performance is going to be terrible.

[Larry Gibson]

I this case "harder" implies too much antimony making the alloy brittle because the antimony is not in solution with the lead. It has nothing to do with "tougher", adding copper, or the BHN. The bullet (Accurate Mold 31-180-F) has a long tapered and unsupported nose with a scrape groove in front of the driving band. That is a very weak point and because of the brittle alloy the high RPM is probably causing the nose to bend and perhaps even partially break at that juncture upon exit from the muzzle. The OP does indeed need to make the alloy "tougher" and more "malleable"....that is done by adding tin, not more antimony.

And the OP needs to back down the load and work back up to where accuracy goes south again. That will be the RPM threshold for that bullet and the other components used. He can then try to push that up by going to a slower powder. With that long unsupported nose he may not see much gain in useable velocity with accuracy though. However, first thing first; correct the alloy and slow the bullet down.

Larry Gibson

[303Guy]

The idea of adding copper is to make the alloy tougher, not harder.

oldandslow, how far into the throat does that boolit drop? You can measure the boolit jump by chambering a loaded round and inserting a cleaning rod to touch the boolit and making a mark then repeat with a boolit lightly pushed into the throat. Too much jump will skid the rifling for sure.

A softer boolit will upset before it reaches the rifling and might engage it properly like in a revolver..

[1500FPS]

And the OP needs to back down the load and work back up to where accuracy goes south again. That will be the RPM threshold for that bullet and the other components used. He can then try to push that up by going to a slower powder. With that long unsupported nose he may not see much gain in useable velocity with accuracy though. However, first thing first; correct the alloy and slow the bullet down.

Larry Gibson

Larry Gibson,

No hold, hang on a minute, I'm confused here with what you said. You said to slow down and work up till the accuracy goes south again. That is the rpm threshold. Now we know that mean the rpm range of bullet. Then you go on to say you can work up with slower power to get more velocity. Now wait a minute, more rpm is more rpm no matter what speed powder pushed the bullet. Explain that. Also how can you be positive the bullet is too hard. That is why the op wants to be able to collect fired bullets undamaged to examine and maybe find out what the problem is.

[captaint]

I would soften it up as per Mr. Gibson's suggestions. Everybody gets caught up in harder, harder. Sounds like the boolit simply isn't twisting up in the rifling as it should. Might go at least half a thou bigger, also. Just my .02. Mike

[tomme boy]

He is say to just start over with what he has.

Then if he wants to go faster, start with a slower powder and maybe a filler of some sort. The slower powder will push the boolit slower at the start to not strip as it enters the rifling. The slower you can push the boolit up to max speed the better. The powder will burn all the way down the barrel instead of in the first few inches with a fast powder. The fast powder slams the boolit and it can deform the nose. This causes a instability. With the slower powder, the PSI builds slower and pushes the boolit instead of hitting it with a hammer.

Clear as mud?????

[mpmarty]

Without the tin the alloy has unabsorbed grains of antimony causing it to fracture and distort. Bring up the tin and bring down the velocity a bit and work back up.

[popper]

Gas checks falling off? I've bored a hole though 4" of pine and didn't find a check anywhere. I soot at a range with concrete slab, don't find any checks lying around. No rifling marks on the base -- I think you mean the rear bands -- too small for bore. You could add some copper to keep the nose from breaking.

[Larry Gibson]

1500FPS

No hold, hang on a minute, I'm confused here with what you said. You said to slow down and work up till the accuracy goes south again. That is the rpm threshold. Now we know that mean the rpm range of bullet. Then you go on to say you can work up with slower power to get more velocity. Now wait a minute, more rpm is more rpm no matter what speed powder pushed the bullet. Explain that.

Yes the RPM will be the same but as tomme boy explains; it's how fast in the barrel you get the bullet to velocity. A slower powder will push the easier and achieve a higher velcocity before the bullet is deformed the same as if a faster burning powder is used. It's the deformation of the bullet from accelleration that unbalances it. It is the imbalances in the bullet that the centrafugal force from the RPM act up. Keep the deformation of the bullet down at a higher velocity and it will remain accurate.

Also how can you be positive the bullet is too hard.

Note I used "hard" in quotations. mpmarty sums it up quite well. I can be positive (to a degree) based on 45 years of experience with cast bullets of all sorts in many different cartridges and firearms. And I will admit; I've been there, done that, got the T shirt.......

That is why the op wants to be able to collect fired bullets undamaged to examine and maybe find out what the problem is.

Yes the OP could certainly do that. The end result and answer however will be the same; add tin to balance the ternary alloy and slow the bullet down.

We can hypothysize all sorts of "possible" solutions but the wheel has already been invented. The OP will be a lot less frustrated, gain success quickly and enjoy casting his own and shooting them if he goes with the obvious solution. I learned the "hard way" as have many others. We're just trying to help and pass on a little of that "hard way" knowledge is all. I learn a lot on this forum as others do.

I also agree with captaint about sizing larger. I'd go with .002 - .003 larger myself.

Larry Gibson

[oldandslow]

Casters, 6/21/13

Larry and 303guy- Regarding bullet hardness- With air-cooled boolits (BHN 8) and 40 grains of 4064 (vel. 2200 ft/sec) I was getting 10" groups at 25 yards (with four shots) and 3 of 4 keyholed. When I went to a harder boolit, 70 degree tap water dropped (BHN 15) my groups shrunk to 4" and 1 of 7 keyholed. With ice-water dropped (BHN 21) the first 6 shots were less than 1" but 9 of the next 12 shots keyholed. Thus it seems like air cooled boolits worked poorly with BHN 15 and possible BHN 21 boolits better.

run5run- I slugged the barrel twice and each time it mic'd at 0.3087". My sized boolits mic at 0.3103-.3105 depending if I use the Lyman or Lee push through sizer.

popper- the boolit is breaking off forward of the driving bands leaving me with the 65 grain base (starting weight 182 grains). I can't tell what the gas checks are doing as they are stripped off when they go through the wet books. The one I did recover was too mangled to get any info.

Ironmike- I'm using Hornady 30 cal gas checks seated at the time of push through sizing.

tommeboy- I don't think it is a sight problem. I'm using a Leupold 2-8 VX3 scope set at 8 power for 25 yard shots off a bench. I followed some of the tumbling boolits with some 150grain Speer boat-tail spitzer points and the three shots were in a half-inch group. So the problem seems to be with the boolits and not the sights. As for the rifle data- it's a Howa 30-06 with 200 handloaded Speer 150 grain STBT through it at medium velocities (2600 ft/sec) so the leade should be good.

1500fps- your thought of slugging the entire barrel to make sure there are no constrictions is an idea I had not thought of (I slug the last 2-3 inches). I would think it would affect the Speer copper clad bullets as well but possibly not.

303guy- the jump from the boolit to the lands is 0.010". I'm wondering if loading the tip of the boolit right against the lands might improve things?

larry- I have some extra tin bars and adding 2% tin sounds like a logical step. Dropping the velocity and boolit rpm down to my 30/30 levels sounds like a good place to start (as the same boolit works fine in the 30/30 at 1700 ft/sec and 102,000 rpm). Since I'm already below the recommended powder charge for my 30-06 at the lowest charge I've tried (34 grains 4064 with 4 of 12 boolits tumbling) is there a certain lower limit I should avoid?

thanks- oldandslow

[bosterr]

A friend of mine just showed me a 100 yd. target he shot with a 309 JDJ 14" Contender. 4 shot group the size of a dime. He took the Lyman mold and cast some bullets, glued 600 grit sand paper to the driving bands and nose (not all at once) and made to bullets a perfect fit in the bore. The nose just gets a little marked by the riflings on chambering. These are traveling at 2300 fps plus. Gator gas checks and homemade lube. These were cast from 50/50 Lino/WW and water quenched. He's shot more groups since then, almost as good. As many a wise men on here has already said, "fit is king".

[1500FPS]

Casters, 6/21/13

Larry and 303guy- Regarding bullet hardness- With air-cooled boolits (BHN 8) and 40 grains of 4064 (vel. 2200 ft/sec) I was getting 10" groups at 25 yards (with four shots) and 3 of 4 keyholed. When I went to a harder boolit, 70 degree tap water dropped (BHN 15) my groups shrunk to 4" and 1 of 7 keyholed. With ice-water dropped (BHN 21) the first 6 shots were less than 1" but 9 of the next 12 shots keyholed. Thus it seems like air cooled boolits worked poorly with BHN 15 and possible BHN 21 boolits better.

run5run- I slugged the barrel twice and each time it mic'd at 0.3087". My sized boolits mic at 0.3103-.3105 depending if I use the Lyman or Lee push through sizer.

popper- the boolit is breaking off forward of the driving bands leaving me with the 65 grain base (starting weight 182 grains). I can't tell what the gas checks are doing as they are stripped off when they go through the wet books. The one I did recover was too mangled to get any info.

Ironmike- I'm using Hornady 30 cal gas checks seated at the time of push through sizing.

tommeboy- I don't think it is a sight problem. I'm using a Leupold 2-8 VX3 scope set at 8 power for 25 yard shots off a bench. I followed some of the tumbling boolits with some 150grain Speer boat-tail spitzer points and the three shots were in a half-inch group. So the problem seems to be with the boolits and not the sights. As for the rifle data- it's a Howa 30-06 with 200 handloaded Speer 150 grain STBT through it at medium velocities (2600 ft/sec) so the leade should be good.

1500fps- your thought of slugging the entire barrel to make sure there are no constrictions is an idea I had not thought of (I slug the last 2-3 inches). I would think it would affect the Speer copper clad bullets as well but possibly not.

303guy- the jump from the boolit to the lands is 0.010". I'm wondering if loading the tip of the boolit right against the lands might improve things?

larry- I have some extra tin bars and adding 2% tin sounds like a logical step. Dropping the velocity and boolit rpm down to my 30/30 levels sounds like a good place to start (as the same boolit works fine in the 30/30 at 1700 ft/sec and 102,000 rpm). Since I'm already below the recommended powder charge for my 30-06 at the lowest charge I've tried (34 grains 4064 with 4 of 12 boolits tumbling) is there a certain lower limit I should avoid?

thanks- oldandslow

Don't give me credit for suggesting to slug the whole barrel as, I believe, that is what Runfiverun was getting too.

One thing bad about tin, if you get too much in your alloy you're going to get leading.

[1500FPS]

[QUOTE=Larry Gibson;2270737]1500FPS



Yes the RPM will be the same but as tomme boy explains; it's how fast in the barrel you get the bullet to velocity. A slower powder will push the easier and achieve a higher velcocity before the bullet is deformed the same as if a faster burning powder is used. It's the deformation of the bullet from accelleration that unbalances it. It is the imbalances in the bullet that the centrafugal force from the RPM act up. Keep the deformation of the bullet down at a higher velocity and it will remain accurate.

Larry Gibson,

Okay, I can chew on the reply you have given. On the other hand isn't the quote above then agreeing with your opponents in the years of on going arguments with saying that all along?

[Larry Gibson]

[QUOTE=Larry Gibson;2270737]1500FPS



Yes the RPM will be the same but as tomme boy explains; it's how fast in the barrel you get the bullet to velocity. A slower powder will push the easier and achieve a higher velcocity before the bullet is deformed the same as if a faster burning powder is used. It's the deformation of the bullet from accelleration that unbalances it. It is the imbalances in the bullet that the centrafugal force from the RPM act up. Keep the deformation of the bullet down at a higher velocity and it will remain accurate.

Larry Gibson,

Okay, I can chew on the reply you have given. On the other hand isn't the quote above then agreeing with your opponents in the years of on going arguments with saying that all along?

And how is that any different than what I've been saying all along? I think you're buying into the oft said, and wrongly said BTW, that the RPM threshold is a set "limit" at a certain RPM. I have consistently said the RPM threshold for a specific bullet in a specific twist may be pushed up or down by the components used in the load, the alloy used and how they are loaded.

I have often said to use a slower burning powder to push the RPM threshold upward. What I've posted on this thread is consistent with that.

Larry Gibson

[1500FPS]

[QUOTE=1500FPS;2270880]

And how is that any different than what I've been saying all along? I think you're buying into the oft said, and wrongly said BTW, that the RPM threshold is a set "limit" at a certain RPM. I have consistently said the RPM threshold for a specific bullet in a specific twist may be pushed up or down by the components used in the load, the alloy used and how they are loaded.

I have often said to use a slower burning powder to push the RPM threshold upward. What I've posted on this thread is consistent with that.

Larry Gibson

Well from reading all the back log of stuff, more like fighting, before I signed up it appeared you said that one cannot shoot a cast bullet from a fast twist barrel with good accuracy. I've been reading so much of it that I'm not going back to look again, probably the reason it took me longer to sign lol, but someone arguing against you asked what if the bullet was near perfect and started perfect then what. At that time you just kept saying it could not be done. All I am saying is, after reading all that stuff (gasp) you have seemed to change your tune. As my handle I'm not into the high velocity stuff just yet, but I sure am reading up on it. So let's make sure I have this correct: If you have a near perfect cast bullet, and you start it into the bore straight and undamaged, that a fast twist barrel can shoot high velocity accurately. Is that correct?

[Larry Gibson]

Casters, 6/21/13

Larry and 303guy- Regarding bullet hardness- With air-cooled boolits (BHN 8) and 40 grains of 4064 (vel. 2200 ft/sec) I was getting 10" groups at 25 yards (with four shots) and 3 of 4 keyholed. When I went to a harder boolit, 70 degree tap water dropped (BHN 15) my groups shrunk to 4" and 1 of 7 keyholed. With ice-water dropped (BHN 21) the first 6 shots were less than 1" but 9 of the next 12 shots keyholed. Thus it seems like air cooled boolits worked poorly with BHN 15 and possible BHN 21 boolits better.

Your confusing the "hardness" based on BHN with the brittleness of your alloy based on too high and antimony content with too little tin. The two are not the same; apples and oranges, etc.

run5run- I slugged the barrel twice and each time it mic'd at 0.3087". My sized boolits mic at 0.3103-.3105 depending if I use the Lyman or Lee push through sizer.

Sizing at .311 would be better if the bullet drops that large. If it does drop at .311 or larger as cast then you may be fracturing the bullet during sizing, especially at the scrape groove in the Lyman pushing down on the nose.

popper- the boolit is breaking off forward of the driving bands leaving me with the 65 grain base (starting weight 182 grains). I can't tell what the gas checks are doing as they are stripped off when they go through the wet books. The one I did recover was too mangled to get any info.

This is the "evidence" that the bullet is too brittle and may be fracturing at the scrape groove during sizing. Your alloy is a combination of lead and antimony not a ternary alloy of lead, antimony and tin in solution. There is a distinct difference and you are demonstrating that difference quite well.


303guy- the jump from the boolit to the lands is 0.010". I'm wondering if loading the tip of the boolit right against the lands might improve things?

That will not help with that alloy and the same load. The alloy is wrong and the load is pushing the bullet too fast. You should be able, with that powder and reducing the load, to get excellent accuracy with that bullet in the 1850 - 1950 fps range.

larry- I have some extra tin bars and adding 2% tin sounds like a logical step. Dropping the velocity and boolit rpm down to my 30/30 levels sounds like a good place to start (as the same boolit works fine in the 30/30 at 1700 ft/sec and 102,000 rpm). Since I'm already below the recommended powder charge for my 30-06 at the lowest charge I've tried (34 grains 4064 with 4 of 12 boolits tumbling) is there a certain lower limit I should avoid?

Not sure how you came up with the "lower limit", especially for 4064 with cast bullets in the '06. That load is still pushing that bullet too fast, especially for that alloy. Add the 2% tin, drop back to my recommended load in my previous post, use the Dacron filler and work back up until accuracy goes south again. Just below accuracy going south with be the RPM threshold for that bullet, alloy, sizing and load combination. You should be able to put 10 shots into 2" or less at 100 yards doing that.

Larry Gibson

[Larry Gibson]

[QUOTE=Larry Gibson;2271005]

Well from reading all the back log of stuff, more like fighting, before I signed up it appeared you said that one cannot shoot a cast bullet from a fast twist barrel with good accuracy. I've been reading so much of it that I'm not going back to look again, probably the reason it took me longer to sign lol, but someone arguing against you asked what if the bullet was near perfect and started perfect then what. At that time you just kept saying it could not be done. All I am saying is, after reading all that stuff (gasp) you have seemed to change your tune. As my handle I'm not into the high velocity stuff just yet, but I sure am reading up on it. So let's make sure I have this correct: If you have a near perfect cast bullet, and you start it into the bore straight and undamaged, that a fast twist barrel can shoot high velocity accurately. Is that correct?

I believe I told starmetal, 45 2.1 and several others at that time that if a cast bullet was perfectly balanced to begin with and exited the barrel perfectly balanced then it would shoot accurately. The trick is to get the cast bullet to come out the end of the barrel "straight and undamaged" isn't it? How many really do that, especially at high velocity in a fast twist barrel......? Getting jacketed bullets to come out the barrel perfectly balanced is the holy grail of bench rest shooting, very difficult to do especially with cast bullets at HV in fast twist barrels. It is the less than perfect, imbalanced bullet (cast or jacketed) that is adversely affected by the centrifugal force of increased RPM while in flight that causes the inaccuracy. The greater the imbalance the less accurate the bullet will be. If you can shoot perfectly straight and balanced cast bullets at high velocity out of fast twist barrels then you are well ahead of the game.

Larry Gibson

[1500FPS]

[QUOTE=1500FPS;2271014]

I believe I told starmetal, 45 2.1 and several others at that time that if a cast bullet was perfectly balanced to begin with and exited the barrel perfectly balanced then it would shoot accurately. The trick is to get the cast bullet to come out the end of the barrel "straight and undamaged" isn't it? How many really do that, especially at high velocity in a fast twist barrel......? Getting jackete bullets to come out the barrel perfectly balanced is the holy grail of bench rest shooting, very difficult to do especially with cast bullets at HV in fast twist barrels. It is the less than perfect, imbalanced bullet (cast or jacketed) that is adversely affected by the centrifugal force of increased RPM while in flight that causes the inaccuracy. If you can shoot perfectly straight and balanced cast bullets at high velocity out of fast twist barrels then you are well ahead of the game.

Larry Gibson

Yes yes that is the guy Starmetal. Okay we're on the same page now. Yes being able to cast them near perfect, not messing them up any in sizing if you have to size, and getting them started straight is a mighty tall order.

[popper]

My GC question was if they were on tight. Evidently they are. I've shot #2, hardball, COWW, my alloy (no tin), AC or ice WD through the AR - feed ramp is a major speed bump, 1:10 twist - with no problems. All my bbls are slightly tapered at the muzzle and throat. I'm still thinking it's a casting or loading problem. You say WW, could there be a high zinc content?

[markshere2]

This thread is like the encyclopedia brittanica of applied cast boolits troubleshooting!

Many thanks to all y'all!

To the last post, Zinc contamination is not likely a problem.
Zinc contamination causes the pour to harden up at a much LOWER temperature and the boolits don't fill out.
it's a gross issue, nothing subtle about it.

In my limited experience...

[303Guy]

... is there a certain lower limit I should avoid?Yes there is - that would be the transonic zone. Way below your range.


... it's a Howa 30-06 with 200 handloaded Speer 150 grain STBT through it at medium velocities (2600 ft/sec) so the leade should be good.Yup. OK, that narrows it down a bit. So it's only the odd boolit that goes sideways. That means you're on the edge. Perhaps seating further out would help. Why not try the same load but with the boolits seated further out so bolt closing does the final seating and see what happens? Funny things with the bore like reverse taper near the muzzle or restrictions in the middle or whatever is not going to cause boolits to go sideways. Rifling stripping will do that, so will too soft an alloy in a fast twist barrel, but for different reasons. It sounds like yours are stripping the rifling. But softer alloy shot poorly - very poorly! Might I suggest adding tin to balance the antimony and using less lead to harden them boolits and reducing the brittleness at the same time? Just to see what happens. Change nothing else. That'll be for one test. Softening the alloy would be as simple as adding some lead should the need arise. OK, first step would be to try seating further out, then add some tin and try that then try a harder alloy. All with the same powder charge. Another angle would be to try the original alloy plus the suggested two, with reduced powder charges.

[oldandslow]

Casters,

So it seems that the general concensus is that the boolits are too brittle at the higher velocity and rpm's with the 30-06 causing the nose to break off above the driving bands (and they do well with the lower velocity and rpm of my 30-30). So my homework next week is to cast some alloy with 2% tin and get out the chrono and start with low velocities (like the 30-30) and see what happens. The good news about failing is that one learns some valuable lessons (but I'm tired of learning this one). Oh well- thanks to everyone and I'll update you as the testing continues.

best wishes- oldandslow

[Larry Gibson]

Failing is many times a good teacher if we pay attention to why we failed. Good lesson here in this thread. Success comes from what we learn and do after the failure. If we fail to learn we probably will fail again until we do or give up. Good thread.

Larry Gibson