Can an AR-15’s headspace change?
I was watching a video where someone was shooting an AR and it had a failure. It was not a catastrophic one though. It appears when they fired the rifle while the casing was being pulled out it tore open near the bottom of the case shooting gas out. Some people commented that the headspace became out of tolerance due to thousands upon thousands of rounds being fired through that gun over the years. Is that a thing? And if so would you just replace the bolt or the whole BCG?
- BBeanLv 72 months agoFavorite Answer
After thousands upon thousands of rounds fired...yes, the headspace could change but also the locking lugs on the bolt and barrel extension could be rounding off edges and the pressure from the case when fired is forcing the bolt out prematurely instead of the delayed action of the bolt carrier body activating the cam action to rotate the bolt. The bolt head only rotates 22 1/2 degrees to lock in and unlock so rounded edges worn to the extent of not having enough holding surface is possible. Normally, the way an AR is designed headspace increasing takes a lot of rounds fired. Heat treating of the barrel extension could be few Rockwell RC points soft and start to stretch like many bolt actions do. Also, reloaded cases that have been worked too many times could also cause what you described. The bolt does give a strong twist when extracting and a dirty chamber could cause the case to resist coming out. There are a lot of things that can contribute to the malfunction you described and without having the rifle in hand is difficult to diagnose.
As far as replacing anything it appears the barrel with extension in place and new bolt are the only two. The bolt carrier body most likely will be alright. I don`t think anyone checks the headspace on new parts because most are held to mil specs.
I have .223/5.56 GO and NO GO headspace gauges and have used them very little and having never checked one that is out of specs it`s easy to take it for granted that it is ok.
- Mr.357Lv 72 months ago
Sure. The bolt lugs or the barrel extension could be worn or broken. If I were going to replace a bolt, I would replace the barrel, or at least the barrel extension. If the carrier and upper receiver were always well lubed and not worn, there is no reason to replace them.