Armscorp receiver, like new USGI H&R barrel, new spring, everything is clean.
I had a local gunsmith install and headspace the barrel. He does a fair amount of M14 work and is familiar with them. I gave him four bolts. He said 2 headspaced OK, the other 2 were dangerous to use.
I assembled the rifle myself. The op rod was tight when going into battery, so I stoned it a little. The rifle then passed the "tilt test."
With no ammo in the gun, the gun cycles manually just as it should.
The only thing I am not satisfied with is the stacking of the op rod spring I feel as I draw the charging handle all the way back.
FWIW, when I received the receiver, I screwed the barrel in by hand and it had too much "draw" according to Kuhnhausen's manual. I didn't say anything to the gunsmith, but they told me they had to remove a bit from the barrel shoulder to get the barrel to headspace correctly. That seemed correct to me. The barrel is indexed very straight; with the rear sight in the middle, and the front sight centered, I am an inch to the right at 100 yds.
When I dropped off the barrel and receiver, I asked where he would headspace it, and he said at the lower end of SAAMI 0.308 specs, and that mil surp would not work. I told him I intended to shoot mil surp, and he said he could set the headspace at the lower end of NATO specs and the higher end of SAAMI specs, IOW close on the SAMMI no go, but not on the NATO no go gauge, and that all ammo would thus work.
I don't know if the barrel is set too far back or not, as the bolt still has a little fore-and-aft movement when in battery (and unloaded); the bolt is not being held back by the breech. However, the other bolt that headspaces correctly, while it will go into battery with light finger pressure(op rod removed, bolt disassembled) there is no perceptible fore-and-aft play. That seems a bit tight to me.
because the rifle ran right through a box of Fed AE without a hitch, but hangs up with Aussie and Port, I suspect it is a headspace issue. Again, the rifle is meticulously clean, and lightly greased all over (except the chamber and areas that would foul the chamber) with plastilube, but certainly not slathered with goop. The rifle locks open on the last round, and it's not much of a bump needed to get it all the way into battery with mil surp, in fact, the hammer will do it (though the rifle will not fire, as it should not).
I don't have headspace gauges for 0.308.
I guess I'll have to improvise as suggested - strip the bolt, and feed in various types of ammo to see which chamber fully without too much effort, and which don't.
That and/or find another gunsmith with the right gauges and the time. The guy who barreled my action has a two-week waiting list....
Thanks all, and keep the info coming!