Quote Originally Posted by lysander View Post
A little over simplification here.

The three prong flash hider remained in service until the barrel assembly it was on was replaced, or the flash hider itself became damaged, the same went for the A1 bird cage.

We had a handful of three prong M16A1s in 1988.

Supplies of replacement A1 birdcages lasted until the 2000s, when they were finally classed surplus to requirements.
Those were some really old M16A1s. The 3-prong FH was dropped from the M16A1 in Dec. 1967. Even the later XM16E1 and Model 604 were eventually outfitted with A1 FHs before ceasing production, but most were produced with 3-prong FHs. The good thing about the 3-prong and A1 birdcage FHs is that they did not need to be timed. The A2 FH does because of the closed portion needing to be on the bottom.