checks that don't get crimped on

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mtngun
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checks that don't get crimped on

Postby mtngun » Sun Mar 23, 2008 5:38 pm

from the old forum:

M95 Styr 8x56R bullet???

I have an 8x56R carbine with a bore diameter of .3175" and a land diameter of .332". I would like to design a bore rider of .333" diameter that uses an 8mm gas check, but your program apparently only allows a .332" diameter with an 8mm gas check. To go to .333 do I need to go to the .338 gc, or can I somehow design a .333" diameter bullet with an 8mm gas check?

Reply: My gas checks are packed at the moment so I don't have a 8mm check handy for measurement, but it seems like I once made a oversize bullet for the 8 x 56 or something similar, with an 8mm check, and the check would not crimp on tight since it was not even being touched by the sizing die. Of course, it was all my fault. Henceforth, the policy was changed to discourage undersize checks.

Question: Dan, you lost me there. Don't you control the size of the gas check recess, diameter and depth, when you cut the mould? You even offer them stepped.

Maybe I don't understand how this works. Please remember, I am a psychologist, not a mechanic of any type. Those of us in the social sciences need physical things explained in simple and complete terms! If you don't believe me, ask LOML, she's a geologist.

I'm asking the question about the 8mm checks simply because I have 2000 of them and nothing, currently, in which to use them!

Reply: Crimp-on gas checks are normally made with an OD about 0.005" - 0.010" larger than the sizing diameter. That way, the sizing die squeezes the gas check and crimps it onto the shank.

However, if the check OD is smaller than the sizing die, then the check never gets crimped.

A common example is the Hornady 45 pistol gas check when used on 0.458"+ rifle bullets. The undersize pistol checks don't get crimped by the typical 0.460" die. It's not a huge problem, and most of the time they shoot just fine even if they are a little loose. But apparently, some folks lay awake at night tossing and turning because they are worried about their gas checks being too loose.

The 8mm check is not big enough to be crimped by a 0.333" die. That means I cannot guarantee a good check fit, and I don't want to go there.

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