I am back again. To answer a guest. byDer Ami, I have done 3 chamber castings[10 days ago] to try to determ. JR orJRS. My final cast with cerrosafe meas..3605dia neck. At 1" from rim of case bore meas..314 to .322,this is a false reading as rifling is such that calipers are not totally on lands or grooves at the same time. Bore cast meas. .309 to.322 ,[ same condition with calipers] I have S &B 8/57jr and jrs factory loads. The JR load without issue however the Jrs insert 3/8" short of chambering. I can chamber it if i use some pressure. I smoked it and it is hanging up on the bullet at about 3/8" ahead of cart. rim. It did not distort in any way after having to force cart into chamber. I am totally confused as cast suggests JRS but chamber say NO. Proofmark states steel jacket bullet
