primer setback

primer setback

[′prīm·ər ′set‚bak]
(ordnance)
The backward movement of a primer cup in a cartridge case which occurs when the base of the cup is not properly supported by the bolt face or breechblock.
McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.
References in periodicals archive ?
The only directions were a sized brass case and standard small primer and we never had any issues with primer setback. Our backdrop was a large thick cardboard box at 7 yards to catch the bullets with a paper target taped over the open front.
I reminded him this difference would at least generate increased pressure resulting in back primer setback plus bulged brass and possibly a blown receiver or bolt face.
Before you start loading your first rounds, a little extra preparation of the brass is required to keep your revolver from locking up after each shot because of primer setback. The reason for this annoyance is somewhat complex but fortunately, simply drilling out the flash hole eliminates the problem altogether.