Who says that cast bullets need to fit the throat?

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  • Last Post 20 September 2017
R. Dupraz posted this 27 June 2017

Some thing interesting happened at the range the other day while fiddling with a 94-30 Venezuelan 7x57 short rifle. This rifle has a .288" throat and .280 bore as per throat slug and the only 7mm bullet mold that I have right now is the RCBS 7mm-145-Sil that drops an as cast bullet that measures .287" base and ..279" nose. 

I got the rifle from a club member who bought it while a college student back in the sixties,the heyday of the surplus military rifles, and then had it sporterized. Stock cut down,drilled & tapped for a scope and bold handle. 

So, I have been dinging around with this combination, just to see if it's worth the time to go further with this rifle. First at fifty yds and then 100.

The other day, advancing out to 100 yds, I loaded some loads with IMR 4227, Alliant 2400 and ten grns. of  Unique. As at fifty, I thought that the Unique loads would be best because of it being a faster powder with the undersized bullet. was true at fifty. 

I had twenty Unique loads among others that were with 2400 and 4227, Ten with the above GC'd bullet run through an NOE push up sizing die of .287". Basically as cast

The other ten had the same load except that the GC'd bullet was sized with a .288" bushing. So that the bullet bands were still .287" but the GC only was sized 288". 

All of the 2400, 4227 and Unique loads with the bullet sized to .287" were pretty much shotgun patterns at 100 yds. Not unexpected. However, the interesting part of this circus was the target shown below. Which was six shots fired after the bullet was run through a .288" sizing bushing. Where the bullet was .287" but the gas check was sized .288", throat diameter.

The only conclusion that I can draw from this is that even though the bullet was undersized the GC was not at .288" Coupled with a fast powder. 

 

Flashback to the 155mm howitzer shooting a 97lb steel bore riding projectile with a very narrow copper-bronze driving band that engraved the rifling. Shot ok. Managed to perforate a corrugated steel latrine that was located on the edge of the impact area once. At about five miles or so. Thought that was pretty interesting. 

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R. Dupraz posted this 27 June 2017

Forgot to mention that the hole in upper left of the target was the poor knave at the bench. Had his finger on the trigger while aligning for the final shot. The above results are consistant with what I got a fifty yds. So, as soon as I get the rifle back from my Smith, who is working some of his magic, I'll give it another go and see what happens.

Still trying to put those "03" shooters in their place with my Mauser's at the military matches.

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Ken Campbell Iowa posted this 27 June 2017

RD ... like to see those 7mm efforts ..  interesting on the gas checks... could it be that easy ??

i have an oversize old west mold for 7mm if you would like to play with it ... might even still have some bullets i cast with it ... hardball tho ...  let me know.

ken

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R. Dupraz posted this 28 June 2017

Thanks for the offer Ken. But think that I'll wait until I get the rifle back and see if I can get a repeat performance. Then, if so, I'll continue to march, if not, guess it will go into the "thought it was a good idea at the time" file. I did come back from the Nat. CBA military tournament with  an any mold in stock NOE gift certificate. So, might use it. Maybe. Got it at the after match drawing. All I go for anyway.

Conventional wisdom, scary thought, says no, it can't be that easy. Do enjoy giving them snooty Springfield shooters a kick in the toosh once in a while with my 98"s. Guess I've never been much of a team player anyway.

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Dirtybore posted this 17 September 2017

R. Dupraz, I loved reading your above posts.  I really appreciate when a sleeper, well you know, one of those odd-balls such as one using a Mauser in the predominately Springfield matches manages to out shine them.  I've done similar at a number of muzzleloader matches.  Anyway, getting back to your 7mm Mauser with it's .288 bore.  You were lucky to get an RCBS mould that would accommodate it.  I worked with a 7mm Spanish Mauser that had .292 grooves and believe me, I never did get that kind of accuracy.  Coupled with that, the rifle didn't have a scope, the lands were worn to nothing at the bore,  and that pharaoh's pyramid shaped front sight  wasn't much help either.  

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RicinYakima posted this 17 September 2017

RD, Missed this post, it was while I was driving around the country after the Military Nationals. Anyway, my friend Joe Gifford was very successful with his 1891 Argentine Mauser with that system. A .313" bullet with gas check seated in a .314" die. Cases just sized about 1/4" of the neck and gas check and the lube space above it in the case. The bullets would wiggle when you touched them. Shot them in a throat that had about an inch of free bore so just the very nose would touch the top of the lands. Powder was 12.0 grains of Unique. He shot a lot of 100's on the old .22LR 100 yard targets. Ric p.s. The bore on the rifle was beautifully smooth and consistent in size.

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358156hp posted this 17 September 2017

I read Joes article in TFS about this, but didn't fully comprehend what he was trying to tell us, he tried to explain it in email as well but I must have been particularly dense at that time. No wonder Joe thinks so highly of that rifle.

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onondaga posted this 17 September 2017

Nobody has to believe anyone that bullets need to fit the throat for accuracy. I offer some logic to support fit:

1) If you have undersized cast bullets they may bump up on firing, that allows bullets to wobble til they fit and decreases accuracy potential from decreased stability at their start down the barrel.

2) Cast bullets of a size that verify in ink a sliding fit of the driving bands on chambering and a bullet engagement of the throat taper to the rifling are held still at the start of charge ignition and have a stable start. This minimizes wobble down the bore and maximizes accuracy potential  of cast bullets.

If you choose to ignore this and other basics like alloy selection to load level relationship, don't be surprised when your cast bullets shoot all over the place. You deserve it for ignoring basics. There are friendlier ways to explain this, but I give up on you beating a dead horse and doing dozens of things that try to compensate for poor cast bullet fit. Blaming throat dimensions and taper angles is meaningless if your bullets don't fit the throat and engage the taper...it is you and a lack of effort to fit cast bullets that shoots your bullets all over the place.

Gary

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R. Dupraz posted this 17 September 2017

Hey Rick. 

Thanks for that information. This is the first that I have heard of that sort of thing with the rifles that we shoot. It sounds like there are some similarities between what Gifford did and how I used to load for my 45x2.4 Sharps. Would make an interesting experiment some time.

The 7x57   barrel that is now on this FN 98 military action also has Belgian proof stamps and was advertised as large ring "new old stock" by a vender on Gun Broker. I don't know about the "new old stock" but is sure looks like it. Perfect unworn shinny throat and bore. Straight and uniform from breach to muzzle. Surprisingly, it screwed right on the action and head spaced perfectly.

The target posted was shot with the barrel at it original length of 29". I have since shortened it to 23 1/2, for various reasons but  it will still hold an inch and a half for ten at 100. Some times less.

The targets that I use at 100 yds for this kind of stuff are left over from my pistol shooting days and are for indoor 50 ft. slow fire pistol.   

 

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Paul Pollard posted this 19 September 2017

Gary,

I have a 6mm barrel which has a worn throat. My mold casts a bore riding nose which measures .236 to .2365, depending on alloy used. The rear bands fit reasonably well, but the nose shows no marks whatsoever. Do you think I should hone out the nose of the mold to fit the nose section of the throat? By doing a chamber slug, it shows that the nose section of the throat is .239. Would this help accuracy or are there other problems with enlarging the nose? 

Thanks

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John Alexander posted this 19 September 2017

Paul, I don't want to butt in on a private conversation but am wondering if this is the barrel and bullet you were using at Pioneer?

John

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Paul Pollard posted this 19 September 2017

Same barrel. The bullet is different. The bullet in question is the Eagan MX2-243 which has always seemed to have a nose too small. Mike Mohler wouldn't use it because of the nose size. It is semi-retired until I figure out what to do with it.

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argie1891 posted this 20 September 2017

Just to add a bitt to what Ric said , when loading for the argie I sometimes had a bullet or 2 pop out of the case on the way to the range. I did my best to seat the bullet just enough so this didn't happen often. From what I have seen most Mauser rifles are a crap shoot on quality, some were made by craftsman others were made just as fast as they could turn them out. Many were made with slave labor during the war. if they went bang they were good enough. I am speaking about those made after ww11 started. those made pre war are mostly good quality rifles, that said most were refinished and the barrels made later just were not of the same quality. I have shot some really great groups with a yougo 8mm with the Lyman 323378 and now N O E is making a copy of it. 

if you think you have it figured out then you just dont understand

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