AR-15/M16 bolt ring / gas ring per MIL 8448511, U.S. Manufacture, pack of 3 or 9 rings.
There was a time when we thought about making improved gas rings. The original design uses 3 thin split rings, ours would be somewhat different. After considerable research, we moved on to something we could actually improve on, for the 3 split ring design is still the best in offering fault tolerance and redundancy. We do not recommend the single ring. With a single ring, you give up 66% of redundancy and fault tolerance, for a
single piece that can unravel when it fails.
This is one of our LMT enhanced bolts. One of the 3 rings is completely missing, the second one is severely diminished, and a piece fell out upon our attempt to remove it, the third one is barely the same shape it used to be. This particular bolt has been in use since 2005, it went through mag dumps at the AZ Big Sandy MG shoots, as well as slow, aimed fire, with various brands of ammo. When dropped into the carrier, it offered almost no resistance. And yet, it was still working.
It is a testament to the brilliance of Eugene Stoner's design.
A simple test of dropping the bolt into the carrier can tell whether the rings should be replaced, the bolt should not drop into the carrier without resistance. While we're at it, we'd be remiss if we didn't mention the futility of aligning the gas rings, it's an old wives tale and has no merits whatsoever. The tapered bore of the carrier closes the split rings as the bolt travels rearward, aligning them is useless and unnecessary.