In that case, is it a timing situation caused by overgassing?
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In that case, is it a timing situation caused by overgassing?
I thought about that. I have no idea what buffer is in the gun or what the gas hole size is.
I assembled an AR for a customer with a custom barrel in 300blk. The barrel was a well known name.
On test firing, it would not cycle. After finally tearing it apart, the gas hole was far undersized- I never checked it before assembly.
In this case, I believe that ammo is .223 not 5.56. It is not particularly hot so unless there is a very oversize gas hole and buffer mismatch it's likely a soft, uncrimped federal primer.
I appreciate all the responses. I rechecked headspace with 2 different bolts, and it seemed to be good. Ammo was factory Hornady Varmint 55 grain V-Max. I’ll have to recheck with 5.56 and see what happens.
I didn't think ar's needed headspacing. Just install barrel and tighten.
They normally do not. What you think of as a barrel is usually a barrel and barrel extension- they're assembled by the manufacturer.
You just stick it in your upper and tighten the barrel nut.
I have been assembling AR's for 30 years and I can only recall a handful that have had headspace issues.
Pretty amazing considering all the various manufacturers that have come and gone over the years.
I've had and seen far more failures in factory ammo than AR headspace issues.
Within the last week I opened a box of Federal .308M 168gn match. One of the rounds has the primer seated backwards, anvil out.
I have to agree with cdi. Primers "Back out" for all kinds of reasons, and I thought that was what the OP was referring to until I saw the photos. That primer looks seated and has nice round edges. The only thing I ever saw that caused something like that was an oversize firing pin hole. Probably bad primers.