headspace

[valsport05]

Could be, but shouldn't be...
Thread crush is minimal when threads (internal and external) are within spec and barrel shoulder and receiver ring are perfectly concentric. There's usually only .001-.0015 crush.

When spinning the receiver onto the barrel, it should spin on smoothly then come to an abrupt and solid "stop" when the shoulder contacts the receiver ring- you can feel it when it's correct. If you have a barrel shoulder or receiver face (or both) that aren't concentric only a small portion of the barrel contacts the receiver face initially- then torque forces the rest into contact. This results in a lot more rotation, and decreasing headspace.

This is why getting fitment correct is critical if trying to get minimal (go +.001 max) headspace.

Very helpful and thorough description, now I'm less concerned understanding it's not necessarily degrees of torque rather proper squaring and fitment of the factory parts to create that solid seating at stop point.

 

[tobnpr]

For peace of mind (never too much of that) do what we all do- punch a witness mark at the barrel/receiver (across both parts like you'd do if staking them) ahead of the recoil lug.
I use a sharpened piece of 1/4" HSS, lay it on and smack it with a hammer. Can't be anything but right when the two marks line up.

 

[valsport05]

For peace of mind (never too much of that) do what we all do- punch a witness mark at the barrel/receiver (across both parts like you'd do if staking them) ahead of the recoil lug.
I use a sharpened piece of 1/4" HSS, lay it on and smack it with a hammer. Can't be anything but right when the two marks line up.

Do this after getting correct go/no go indications to be able to check for any movement after/during use?

 

[tobnpr]

^^^
Yessir.
With proper torque no barrel should ever vibrate loose, primarily for checking that the barrel is clocked correctly when re-installed if it's been pulled. A lot of shooters swap shouldered barrels same as others do nutted barrels, with no gauge needed- just line up the witness marks.

 

[nksmfamjp]

With proper torque no barrel should ever vibrate loose

What is proper torque?

 

[tobnpr]

^^^
No firm consensus there... like much in this discipline.
I go 60-80, some go as much as 100.

I've never felt it is a critical value (as in, I do not use a torque wrench). Others may disagree with that assessment.

 

[chav0_12]

^^^
No firm consensus there... like much in this discipline.
I go 60-80, some go as much as 100.

I've never felt it is a critical value (as in, I do not use a torque wrench). Others may disagree with that assessment.

I use a torque wrench and get it up to 60 but no more. It's also a very cheap torque wrench so the numbers could be way off. Also, I'm shooting a 28 Nosler and not exactly light in the loads. Tight is tight, witness marks would show it you create a dangerous situation.