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what bullet length (Read 5678 times)

QuestionableMaynard8130 Frequent Elocutionist Offline Posts: 4144 Location: Benton Harbor MI Joined: Apr 17^th, 2004	what bullet length Jul 17^th, 2017 at 11:45pm	Print Post
	for optimum cast bullet accuracy, .375 bore, 1/12 twist probably using harder alloy than standard 20/1 oh yeah the rifle is in 375 H&H

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QuestionableMaynard8130 Frequent Elocutionist Offline Posts: 4144 Location: Benton Harbor MI Joined: Apr 17^th, 2004	Re: what bullet length Reply #1 - Jul 18^th, 2017 at 9:56pm	Print Post
	I'm a bit surprised that with all our attention and comment on cast bullet design no one has offered an opinion or advice. Just wondering with that bore and twist what bullet length will stabilize best. from the chamber cast it looks like there is nearly 3/8" from the actual case mouth to were the rifling begins to show. the factory bullets i have on hand----if seated so that they can be crimped in the bullets crimping groove would have a neck of a jump to the rifling. of course in a repeating rifle the rounds would have to have a pretty hard crimp

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bruce moulds Senior Forum Member Offline Posts: 290 Location: the antipodes Joined: Mar 14^th, 2015	Re: what bullet length Reply #2 - Jul 19^th, 2017 at 6:48am	Print Post
	in a magazine 375 h&h rifle, crimp has proven to be unnecessary with reasonable neck tension. in a double it might be more important to keep bullets in the case. keep safe, bruce.

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Cat_Whisperer Frequent Elocutionist Offline No 1, 9.3x74R Posts: 3987 Location: Mountains of Virginia Joined: Apr 17^th, 2004	Re: what bullet length Reply #3 - Jul 19^th, 2017 at 6:57am	Print Post
	bruce moulds wrote on Jul 19^th, 2017 at 6:48am: in a magazine 375 h&h rifle, crimp has proven to be unnecessary with reasonable neck tension. in a double it might be more important to keep bullets in the case. keep safe, bruce. Agree. I think that .002 or .003" tension holds the bullet MUCH more than a crimp. But then, the issue of where the bullet is placed - I usually start .010 back from the rifling with jacketed and just into the rifling with cast. Jump isn't always a bad thing for cast. I had a .357 Max barrel that wouldn't shoot with cast - but the current owner uses .357 Mag in it and it works WELL!

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QuestionableMaynard8130 Frequent Elocutionist Offline Posts: 4144 Location: Benton Harbor MI Joined: Apr 17^th, 2004	Re: what bullet length Reply #4 - Jul 19^th, 2017 at 7:36am	Print Post
	my experience (or lack there of) has me of the opinion is that "jump" from case mouth to rifled bore is OK. ------ As long as the bullet goes in straight and true with no upset, and that the bullet base is not deformed in a non-symmetrical way in the process. The bullet's shape & alloy as well as the pressure and nature of the powder would all have an impacting factor. I understand that is why we breech seat; to place the bullet as carefully aligned as possible---prior to igniting the powder. I suspect that shooting cast bullets as "fixed ammo" from the case in a "free-bore" chamber might experience issues as they slammed into the rifling.

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alex henry two Participating Member Offline Posts: 25 Joined: Mar 22^nd, 2015	Re: what bullet length Reply #5 - Jul 19^th, 2017 at 7:01pm	Print Post
	Hi, Bullet length for you would be 1.506". Using borex3 answer x itself. then x twist x .07. Then divide first answer by the second answer will give length of bullet to whatever range you wish to shoot, Works for me. Vic .


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QuestionableMaynard8130 Frequent Elocutionist Offline Posts: 4144 Location: Benton Harbor MI Joined: Apr 17^th, 2004	Re: what bullet length Reply #6 - Jul 20^th, 2017 at 6:50am	Print Post
	???????????

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alex henry two Participating Member Offline Posts: 25 Joined: Mar 22^nd, 2015	Re: what bullet length Reply #7 - Jul 20^th, 2017 at 6:56pm	Print Post
	Hi, .375x3=1.125x1.125=1.265625. 12twist x .07= .84 1.265625 divided by .84= 1.5066964. Used this method on all cal for smokeless and black powder. Vic.


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beltfed Frequent Elocutionist Offline Posts: 1826 Location: Central Wi Joined: Dec 20^th, 2007	Re: what bullet length Reply #8 - Jul 20^th, 2017 at 7:36pm	Print Post
	Vic, Can you please tell us of the source/derivation of your formula for calculating bullet length vs caliber and twist? I am familiar with and have used the Greenhill formula and also Greenhill as modified for our slow cast bullets. but do not recognize your formulae. thanks beltfed/arnie PS, I am not necessarily disputing the result of 1.50xx" for (max) bullet length for the 12 twist 375Mag.


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John Boy Ex Member	Re: what bullet length Reply #9 - Jul 20^th, 2017 at 7:40pm	Print Post
	Quote: Hi, Bullet length for you would be 1.506". Using borex3 answer x itself. then x twist x .07. Vic, am intrigued. Do you have a purchase link for the Borex3? And how is it used?


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Dellet Frequent Elocutionist Offline Posts: 1310 Joined: May 19^th, 2017	Re: what bullet length Reply #10 - Jul 20^th, 2017 at 8:21pm	Print Post
	Kind of an interesting formula. Running it for a caliber I am more familiar with, .308 and a 10 twist, comes out at 1.219". If I did the math right. A Sierra 175 SMK is 1.240" Sierra 168 SMK is 1.215" For choosing a bullet without considering velocity, it came very close to some known performers. I wonder with cast if it might be more accurate?


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alex henry two Participating Member Offline Posts: 25 Joined: Mar 22^nd, 2015	Re: what bullet length Reply #11 - Jul 20^th, 2017 at 11:44pm	Print Post
	Hi John, Typo error Bore diameter x 3. Second post sets it out, I also take groove dia instead of bore dia witch changes things a bit. Vic.


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alex henry two Participating Member Offline Posts: 25 Joined: Mar 22^nd, 2015	Re: what bullet length Reply #12 - Jul 20^th, 2017 at 11:53pm	Print Post
	Hi Dellet, I found info on webb forget where but found it works on black powder vel, some say longer bullets but they run out of puff a longer rangers without bumping up vel, Heavy and slow is the go. Vic.


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craigd Frequent Elocutionist Offline Posts: 2059 Location: midwest Joined: Feb 22^nd, 2009	Re: what bullet length Reply #13 - Jul 21^st, 2017 at 6:08pm	Print Post
	There's a group mold over at noe that was designed by Frank here to come in at 1.33" with an elliptical nose and 330 something grains. I believe it was intended for a 1 in 14 twist barrel. The 1.5" length is probably about right. You can peak at Sagebrush molds for their comments about a 1.465"/368gr. intended for the 1 in 12 twist at cast bullet velocity.


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Dellet Frequent Elocutionist Offline Posts: 1310 Joined: May 19^th, 2017	Re: what bullet length Reply #14 - Jul 21^st, 2017 at 8:05pm	Print Post
	alex henry two wrote on Jul 20^th, 2017 at 11:53pm: Hi Dellet, I found info on webb forget where but found it works on black powder vel, some say longer bullets but they run out of puff a longer rangers without bumping up vel, Heavy and slow is the go. Vic. The difference will be basically G1/G7 BC model bullet shapes.


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