Gas gun neck tension?

Sgt_Jamez

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Dec 24, 2009
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Carmichael, CA
Specifically I am loading Grendel rounds. I am going to order the Redding Type S FL sizer and needing a shove in the right direction. Reading the Redding website, they state that a bushing selection of .001" - .002" less than the neck OD of a loaded round is recommended. Then other sources state .002" - .003". So my question is what is the proper neck tension for an AR-platorm gas gun with focus on the 6.5mm Grendel (if that matters). Thanks!
 

ChadTRG42

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Jan 22, 2007
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Re: Gas gun neck tension?

Most standard FL dies will put about .004 to .006 neck tension. This works fine. When measuring for neck tension, if you go with only .002" tension, some cases will have less tension on them. This can cause issues with the bullet sliding in or out during recoil or just handling the ammo. I ran .002" tension for my 300WM ammo, and increased it wo .004" for this reason.
 

Sgt_Jamez

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Re: Gas gun neck tension?

I currently have a Forster FL sizer and after chambering a round, the bullet slips several thousandths. If forget the exact number. Could this be solved by polishing the expander? Or would I be best off just moving to the Redding Type S?
 

Fuzzball

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Jan 19, 2009
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Re: Gas gun neck tension?

"Gas gun neck tension?"

No matter how small the hole in a case neck is, the "tension" (it's actually an interference fit) is limited to about .0015". Making the hole smaller only increases the seating effort and, usually, bullet run-out. The bullet will simply act as an expander for a smaller hole because the elasticity limits of brass will not retain any more "tension" than that.

Measure the diameter of a loaded neck, then pull the bullet and measure it again. You will find the actual amount of elasticity your cases can allow. It may vary a half thou one way or the other from around .0015" but I've never seen any more than 2 thou, and only rarely that much.