Failure to chamber with magazine?

[everyreggie]

I have a .264 lbc upper built by Les baer, I have fired over 3000 rounds through the rifle and have a few dificulties but nothing that was't quickly fixed once I realized that i was a moron and did somthing wrong. This time I am perplexed!

I was at the range shooting reloads ( they have all been resized and checked through a wilson gauge). The first ten or so rounds ran flawlessly, but all of a sudden CLICK! The bolt stopped just short of chambering, and was stuck. Now at first I thought this was my rounds but once i dropped the mag and hand fed the round, it fired perfectly!
So the next mag went in and the exact same thing happened, again i hand fed the rounds and they worked. This happened with all 4 mags I ran.

Now i am ok with coincidece, but all four mags failing, the odds are unreal!

Any ideas would be appreciated!! thanks

PS this is a new bolt from les baer with about 300 rounds on it!

[stokesrj]

I'm thinking you have rounds that are at or near max headspace. The reason they work if fed directly into the chamber is that the higher bolt velocity is able to force the round into the chamber. When fed from a magazine the bolt velocity is slowed down because of the added friction. If you turn your sizing die down another 1/4 turn I bet all will be well.
It is difficult to see just .001 or .002 over spec with a wilson gauge. You almost need a straight edge like a razor blade to feel it.
Take a look and see if that isn't the case.
Bob

[RStewart]

I'm thinking you have rounds that are at or near max headspace. The reason they work if fed directly into the chamber is that the higher bolt velocity is able to force the round into the chamber. When fed from a magazine the bolt velocity is slowed down because of the added friction. If you turn your sizing die down another 1/4 turn I bet all will be well.
It is difficult to see just .001 or .002 over spec with a wilson gauge. You almost need a straight edge like a razor blade to feel it.
Take a look and see if that isn't the case.
Bob

I agree. When I first started I found my Grendel was doing exactly the same thing described. Bumping back the shoulder cured the problem.

[jkingrph]

I agree. When I first started I found my Grendel was doing exactly the same thing described. Bumping back the shoulder cured the problem.

Same here, I cured my problem by slowly "lapping" a few thousands off the upper face of my case holder so the cartridge can enter the die just a little more. Don't know what the exact measurement is but I lapped it using some fairly fine w/d sandpaper on a flat plate until i just got reliable chamering and lock up. It took a while making dummy rounds to test but was worth the effort.