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Rate of Headspace Change with New Barrel?

Religious Shooter

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I shot my LR308 in .308 yesterday. I used a go gauge previously and found the chamber to be on the short side. I was having closure problems at the range.

I measured the fired cases and I got an average of -1.3 with my RCBS MIC. The reloaded ammo I was using was averaging -2. I measured some unfired factory ammo with my MIC and got an average of -2.9.

I was planning to set back the shoulder of the brass for this gun to around -5. So there would be about 5-1.3=3.7 thousands of gap. I was going to load 50 or so and function fire again. If the new set-up worked I was going to load a 1000 or so rounds.

What I'm concerned with is how much the headspace would grow within the first 500 or so rounds of a new barrel. I don't want to have loaded a 1000 rds only to find out that the headspace changed significantly before I had shot the 1000 rds.

Should I shoot 200? 300? or ? before I load up the 1000 rounds?

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I do not have nearly as much experiance with 308 as I do with 223 but what stands out to me in your post is that your re loads miced bigger than the factory rounds and you already know the chamber is tight. I personally would make adjustments to mirror the factory rounds and try it again. I doubt headspace of the rifle will change much in only 500 rds. It did not change at all that I could measure in my Tac-20 after several thousand rounds.

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It's common to check used/old rifles for excessive headspace. I would think that old/used rifles are checked because of wear?

I don't know for sure. But the replies I'm getting on the other boards are saying that the chamber headspace area doesn't grow/erode. They are contending the change can happen with bolt area (lugs and maybe face). Wear there can change the headspace.

But... as you shoot a gun the chamber gets hot. You are shoving the cartridge into the chamber... the brass is expanding and is smacking the chamber...

You take any piece of metal... you heat it up and you tap it hundreds/thousands of times. Sometime it retains its shape. Sometimes it doesn't.

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agree'ed, but like others have said, I guess on other forums, the headspace issue will be because of bolt locking lug issues/wear or even breechface erosion.

I say while you have the press set up, crank out maybe 50 rounds at where/whatever shoulder set back you feel you need, take them to the range to test them out. if they function Okay and print acceptable enough groups, go back home and crank out the other 950 rounds.

your "leades" will be the thing that erodes first.

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