Question and intro - Do barrel extensions ever fail?
First, an introduction...I am pretty new to the AR game, but long enough to have learned a lesson or two. I bought a Bushy as my first AR and soon discovered it had a .223 chamber instead of .556. Pressures were so high I could feel the gas escaping with my left hand from under the FSB. Robb Jensen and his Christiansen reamer took care of that. But I eventually sold that and ended up buying an LMT. I also have a Colt 6920 and a BCM M4 MOD2; so I have learned a lot by just lurking here for a while. Buy top tier stuff and you won't regret it, although I admit it is a sometimes a source of amusement for me to watch someone try and justify their choice of inferior products. I have always believed the gun-ammo combination is a system and as such I use only high quality ammo (IMI M855 almost exclusively) whenever possible. All the guns have Aimpoint M4S sights, which to me are outstanding sights.
I am not a police officer, service member, operator, or anything like that...and will never pretend to be. I work for the US Army as a materials scientist (civilian) and between that and kids I don't have much time for much else. I shoot when I can, just for fun. One day I hope to take a carbine course though. Until then, my plan when visiting here is to keep my ears open and my mouth shut for the most part. By the way my handle/avatar is named after the giant Carboniferous-era dragonfly with the 3 foot wingspan, in case anyone wondered.
Now for my question - I know from an email query to BCM that at least their barrel extensions are type 8620 steel. The barrel extension has plenty of stress placed on it during firing. The lugs on the barrel extension seem to be vulnerable just by virtue of their geometry. How is it that those never break, whereas bolts breaking seems to be a regular occurrence?