Colt AR question

[USSA-1]

Haz,

Those are KNS anti-rotation pins.  They keep the hammer and trigger pins from drifting out of the receiver as well as keeping the pins from rotating within the receiver holes.

You see them more on full-auto setups so the steel pins don't rotate and enlarge the holes in the aluminum receivers, ruining what is a very expensive investment. 

How effective they are is open to debate, but it's cheap insurance against ruining a CIII transferable FA receiver.

USSA-1

[Hazcat]

Thanks USSA-1,

Mine is NOT FA but I was told it had 'trigger work' done to it.

[Big Frank]

Bidah was right when he said it didn't look like the KNS non-rotating pins, and USSA-1 was right when he said they are KNS. It's the NEW GENERATION 2 PIN SETS that don't look like the KNS design many of us have seen before. None of the thousands of M16s I inspected and worked on in the army had loose pin holes in the receiver so I doubt non-rotating pins are actually needed.