Sizing on projectiles?

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Sizing on projectiles?

Postby benny on Mon Aug 21, 2017 10:33 pm

I see some of the pistol projectiles are sized .001 to .002 larger than others in the same caliber. IE : .45 comes in .451 and .452 the 44 cal comes in .429 and .430,
Why is this and does it matter which size you use I any given recipe?

Beny
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Re: Sizing on projectiles?

Postby 870TC on Tue Aug 22, 2017 6:45 am

Lead bullets are usually sized larger so they will obturate in the bore (seal so no gas gets around the side of the bullet to create leading)
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Re: Sizing on projectiles?

Postby aprilian on Tue Aug 22, 2017 8:10 am

For best accuracy, some competitors slug their barrel and then go .001 over with bullet size. Not all barrels are the same internal diameter.

In my limited experience, softer bullets can also not obturate because of being sized down by insufficient case diameter (from the expander die). Remember, lead is softer than brass. I had some swaged bullets that were reduced by .001 diameter just in seating. Swapping the expander die has cured that problem. Also, I find that many lead bullets tend to run closer to .453 and the jacketed run a more consistent .451.

That's the long way of answering your question on which size you should use; "It depends" on a lot of different factors. Luckily very few bullets are available in both sizes (i.e. .451 and .452) so picking the type of bullet usually gives you the diameter you will be using.
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Re: Sizing on projectiles?

Postby noylj on Tue Aug 22, 2017 9:50 am

No, it really makes no difference from what I can see if the bullet is even 0.002" over the nominal size.
I find that 0.356-0.357" jacketed bullets give better accuracy in 9x19 and 9x21 and lead bullets do much better if they are 0.357-0.358".
I always start at the start load and work up and have never seen any problems.
If you don't know the groove diameter of the barrel, any barrel, you are just guessing about what bullet diameter to use.
.223 Rem has a groove diameter specification of 0.224-0.226". If my .223 has a 0.225" groove diameter, I will certainly test 0.225" bullets. SAAMI spec for .223 Rem bullets for use by the industry in ALL guns is 0.2215-0.2245", but I don't load for ALL guns.
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