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Cast bullet diameter based on alloy? (Read 1157 times)

Smoke Oldtimer Offline Posts: 755 Location: San Diego Joined: Feb 24^th, 2013	Cast bullet diameter based on alloy? Aug 16^th, 2021 at 3:08pm	Print Post
	I need to order a bullet mold for a rifle with a bore diameter of .318 and a groove diameter of .327 How much difference, and in what direction, is there between a bullet cast from 30:1 and one cast from 40:1? I want to be sure that it will cast at least a .328 bullet and want to be able to play around with alloys. I won't even care if it casts at .330 as I can always run the bullets through a Lee sizing die.

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JLouis Frequent Elocutionist Offline Posts: 10625 Joined: Apr 8^th, 2009	Re: Cast bullet diameter based on alloy? Reply #1 - Aug 16^th, 2021 at 3:24pm	Print Post
	Based on my mine own mould making experiences and all of the variables involved you might be trying to cut it to close. I would also encourage you to take the freebore diameter into serious consideration. To insure that the targeted base diameter is not smaller than the freebore diameter itself.

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rgchristensen Frequent Elocutionist Offline Posts: 1146 Joined: Jan 2^nd, 2014	Re: Cast bullet diameter based on alloy? Reply #2 - Aug 16^th, 2021 at 4:17pm	Print Post
	Start with a "big enough" bullet and size it down to where you want it. I have sized .40 cal bullets down from .412 to .3995, and they shot two consecutive 5-shot groups, bench/scope, that could almost be covered with a quarter. This with a muzzle-loading rifle. They were pre-lubed and sized nose-first, in a properly tapered die. Common "lubrisizers" can be very damaging to bullets, especially if they are used to reduce the diameter. The diameter of bullets will change with the melting point of the alloy. The bullets are formed at the freezing point, and will contract a bit as they cool to room temperature. The richer alloys (more tin or other metals) solidify at lower temperatures than pure lead, and therefore shrink a lesser amount. There are other factors, such as mould temperature, but the melting point of the alloy is the most important. CHRIS


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Jeff_Schultz ASSRA Board Member Offline Posts: 1631 Location: Ransomville, NY Joined: Apr 25^th, 2004	Re: Cast bullet diameter based on alloy? Reply #3 - Aug 16^th, 2021 at 4:33pm	Print Post
	You will not be able to measure the difference in diameter between 30-1 and 40-1; the difference in weight will be obvious, perhaps as much as 2 grains.

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Smoke Oldtimer Offline Posts: 755 Location: San Diego Joined: Feb 24^th, 2013	Re: Cast bullet diameter based on alloy? Reply #4 - Aug 16^th, 2021 at 7:03pm	Print Post
	Jeff_Schultz wrote on Aug 16^th, 2021 at 4:33pm: You will not be able to measure the difference in diameter between 30-1 and 40-1. ... That's all I really needed to know. I'll just get it at .330 and size 'em down. Thank you!

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