I've had my Bushy M4 copy for a couple of months now and it shoots really well.  This past weekend I was at the range sighting in and when I took the rifle off of the stand I was using, I noticed a small "C clip" type fastener lying on the front support of the rifle rest. I saw it after I pulled the pivot pin and opened the rifle (pulled the bolt, carrier and charging handle for cleaning).  The c clip is about 1/2 inch in diameter and the inside diameter is roughly the size of the pivot pin or takedown pin.  It's finished in a dull matte black/gray color (lighter than the rifle finish), and it appears to be steel.  I went through the whole rile, the handbook, and the Marine M-16 handbook, but could not locate anything that looked like this part. I also didn't see anything which looked like it was "missing" from the rifle.  I didn't take the bolt out of the carrier at the range, and checked the 3 rings on the back of the bolt, and they are still there.  Can anyone help with the ID of this part? From where it was, it really looked like it came from the rifle (no one else used the rest, and my buddies were not there on Saturday, which eliminates the possibility of one of them putting a part that looked like it came from the rifle on the rest to drive me nuts trying to find out where it came from).  Sorry for the long post here, but I've been trying to find out what this c clip is and if it came from my rifle or not. Thanks.
Shoot-n-Fish

Sounds like maybe it's a gas ring?


[Edit]Started thinking about it, and I have no clue how a gas ring would fall out.  Plus, I've never seen one that wasn't silver colored.

So, I don't think that's what it is.

Like brouhaha said, I cannot think of any part it could be except a gas ring from your bolt.  Look closely at the bolt and see if it is the same.  Also, like he said, I don't see how it could fall out unless it was broken.  Watch-Six

Shootnfish,

Do you know how to take apart the bolt to get to the gas rings?

the only c type of fastener I know of on the ar is the tiny one for the dustcover hinge pin.good luck.

did you check the ejection port cover?  Just guessing on this one.

Some anti-walk pins have c-clips on them - but they are not a standard Bushmaster part.  The only time I have seen them used is on the sear pin on an M16.  

I would take it back out shooting and watch carefully for anything coming apart.  Are you sure the c-clip wasn't sitting on the rest before you used it?

Wow, I feel better now.  I did check the gas rings and all three of them are there.  Also the retaining ring on the dust cover is there.  The C clip is a little larger in diameter than the gas rings and it has a gap which is much larger than the gap in the gas rings.  The more I hear, the more I'm convinced that it probably came off of someone else's rifle and just happened to land on my rifle rest. I really went through all of the parts of the rifle that I could, and really looked to see if it would fit anywhere, and I couldn't find a place where it would even look right being there.  Thanks for all of the quick replies.  I'll just hold on to it and if something becomes fubar in the rifle, I'll know what’s missing. Thanks.

Shoot-n-Fish