You need to figure out why the rounds are not chambering. What COAL are your rounds at? 1.142? Usually the max COAL is spec’s @ 1.169, so 1.142 should work in most guns. What firearm are you having the issue with? Definitely check case diameter. Perform a plunk test using a Sharpie marked case and try to figure out why the rounds aren’t chambering before shortening COAL.