Failure to chamber with magazine?

[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.