What would cause the gas rings to break? I noticed while cleaning my bushmaster m4 the other night that one of the gas rings was missing about 30-40% of its body. I didnt find the missing portion anywhere in the upper or in the lower. I am almost 100% sure i have fired the gun since the gas ring broke because this is the first time i have taken the bolt out of the carrier in about a month. Would firing it like this be un safe? I am ordering a set of rings but they wont arrive till next week.

I have seen this on more than a few occasions.  I have never found the missing piece, either.  But the rifles continued to function just fine.

You should always have spare gas rings anyway.  You might want to consider the one-piece McFarland rings which several manufacturers are supplying on new rifles now.

I just installed a Mcfarland one piece ring on my M4 bolt (in addition to a Wolff extractor spring and D ring) and sagging reliability was upped to total reliability.

Get away from the old three set rings and go Mcfarland. I don't know who all is selling them but mine came from Armalite. About $1.25 apiece so I stocked up on several.

I agree, McFarland is the way to go.  I also ordered my from Armalite. matter of fact, Armalite use the McFarland on all their rifles.