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Bullet weight and bearing surface?

 
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Old 03-21-2012, 11:38 PM
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Bullet weight and bearing surface?

When weighing out bullets and also when measuring bearing surface how much variation should I allow?

I am using .257 115gr Berger VLDS. When weighing there were a large group in 115.0 and 115.1gr with about 1/3 as many in the 114.9gr and 115.2gr

However, when measuring bearing surface they ranged from .477 to .483
Most were in the .480 and .478 cups with lesser amounts in the .477 and .481 cups then a few in the rest. Sure seemed like they were all over the scale.

Agin what should I seperate at? Thank's, Brad
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Old 03-22-2012, 04:55 AM
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Re: Bullet weight and bearing surface?

You don't say how many were measured and weighed. A weight difference of .3 grain in a lot of 100 is insignificant. That is why I no longer weigh Bergers.

Same with bearing surface. A difference of .006" is very good. First of all, your use of caliper and measuring technique must be exact each time. Even so, it will be difficult to bring the BS differential down to zero. What tools are you attaching to the calliper?

The real test is shoot them by lots at 500 and decide whether you see a difference. My guess is you will not.

You can, of course, separate after weighing or checking BS. Put them in three lots (high, low, medium). Keep the mediums for target work; cull the others and use them for sighters.
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Old 03-22-2012, 05:11 AM
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Re: Bullet weight and bearing surface?

Here is a perspective that I think should be considered: You got it all backwards.

You really should be figuring out what you need first, and then measuring to find it. Or, measuring as part of YOUR determining what you need, and then measuring to find it.

Without detailed qualifications(of your measurements) we don't even know where the variances apply toward internal or external ballistics theoretically. And we can't fire those bullets for you, in your gun, across a known good chronograph, with a fully developed load, a good target scope & properly prepped brass.
So there is no way we could tell you what to do with your actions so far other than to test for results of it, or misguide you with our anecdotal hogwash.

For that, from me, I say you won't see a bit of difference that you can prove on target -until you do.
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Old 03-22-2012, 07:54 AM
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Re: Bullet weight and bearing surface?

I'm using Hornady lock and load comparators and comming up with the deviations I told you. I seperated 200 bullets by weight and probably 50 by bearing surface.

I'm really just wanting to know how much deviation do you normally allow for your precision shooting? Expample: weight 1/10 gr either way so no 2 are more than 2/10 gr diffrence and bearing surface .001 either way so no 2 are more than .002 diffrence etc.... Thank's, Brad
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Old 03-22-2012, 09:05 AM
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Re: Bullet weight and bearing surface?

My constraints are wider than that. With bearing surface, I will accept up to .004" as keepers; any above or below that are sighters.

Weight, bullets within about .3 grs are keepers. Over or above that I use as sighters. But again, I do not think it is necessary to weigh Bergers.
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Old 03-22-2012, 04:00 PM
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Re: Bullet weight and bearing surface?

Thank's Gene. Brad
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