To crimp or not to crimp, that is the question.

[thermaler]

short barrel AR's are hard on case heads, not case necks. They're hard on case heads because the gas system is shorter than it should be when you start with a chopped down barrel length. We still have to keep the gas system in play and the gas port has to be before the barrel ends so it ends up moving closer to the chamber in short barrel models where the pressures are much higher and viola, you have early opening of the bolt and all the evil that comes with it. The early opening (compared to a proper rifle length AR with a rifle length gas system) causes the bolt to rotate such that it tries to spin the case inside the chamber while there's still pressure in the tube holding the brass against the chamber walls. The brass doesn't want to move (inertia + friction) and is forced to. This stretches and works the brass and eventually will cause a failure. EVENTUALLY either it'll rip a case head off (leaving a case body in the chamber and causing the biggest headache of failure types) or just damage a case so that it splits down the side or succumbs to incipient case head separation. You see this issue a lot with the really short AR-15's that are so popular lately but the problem exists any time you try to shorten an AR gas system and gets worse the shorter the barrel gets and the nearer to the chamber the gas port gets.

I went through months of issues with AR's. I was not taught to reload for them, I learned the hard way, by having one idiot problem after another and then sitting down and reasoning out the "why" of each failure until I got a pretty solid idea of what was going on. Wait till you start working with powders that are great in a bolt gun but wretched failures in a gas gun. Then it gets interesting.

Hmmmm interesting stuff since I haven't reloaded for an AR yet. I have a 16" 5.56 carbine that I recently bought a Stag 16" 6.8 spc upper for with the specific intent of reloading for it to fine tune the ideal load for. I also have an LRT SASS with 18" bull barrel--would the mid-length system be less prone to this type of failure?

BTW--just got back from my LGS and the reload guy (says he's been doing it for over 51 years,he's kinda like Levon Helm in "The Shooter") tells me of a guy who just bought a Bushmaster AR and stuck his reloads in without resizing the brass--apparently blew it to pieces--but Bushie for some reason agreed to give him a new rifle no charge.