Safe Barrel Spec.


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25cschaefer
February 13, 2014, 08:32 PM
I am building a 50BMG bolt gun in school an am trying to build it correctly, i.e. safely, but for little cost. I am using only 4140 steel for the receiver and barrel accessories and am having it professionally heat treated.

My question is: does anyone know what the US military does/did use for bore and rifling specifications? I know that 50 BMG barrels are supposed to be .500 lands and .510 bore but what are the Mil-spec tolerances?

I have the opportunity to buy a factory second barrel from a very good barrel manufacturer that is .0005 small on both dimensions. I am wondering if the military would have found this acceptable.

I am not building a benchrest rifle. I am not building a benchrest rifle.

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rcmodel
February 13, 2014, 09:02 PM
I don't know what the +\- mil-spec tolerance is.
But rest assured it is more then that.

But 5/10,000" is so small you could lap it out with bore paste on a lead slug in 30 minutes.

And I don't believe it would make any difference if you didn't.

IMO: .005" would truly be a deal breaker, but .0005" isn't.

rc

25cschaefer
February 13, 2014, 11:39 PM
Thanks RC, that's what I was thinking, I wouldn't have even known if the maker hadn't told me.

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