Colt SP-1 question: what the heck is this?

[thebearpack]

Is this a .223 primer just out of curiosity?





OK, long story short, I am NOT an AR guy so bear with me if my terminology isn't correct or if this is a stupid question. In general, ARs don't do anything for me. I love mil-surps... I'm just a walnut stock sort of guy. But there was something about the retro look of the SP-1 that I dug so when I had a chance to buy one at a good price, I did. I took it to the range and instantly loved the feel of the rifle and to my surprise it was very, very accurate even with the ridiculous factory trigger it had. I was hooked. So I researched 2-stage triggers and bought a RRA NM 2-stage drop in. I read up on how to do the swap and it seemed pretty easy.

When I took off the pistol grip to remove the safety lever, the little part shown in the pics below dropped out along with the detent pin so I just set it aside. Couldn't find any SP-1 schematics so I figured I'd deal with it later. Today the RRA trigger came so I put it in but when I was reassembling the safety I remembered this part. After I got the new trigger in I did the function tests listed in the instructions and everything seems to work just fine. So my question is, is this a stray primer or some "extra" part I need to be concerned with? I'm guessing it's something obvious so one of you AR guys is probably saying "NOOB, it's an XYZ... duh!" and even though I assume it's a primer I just want to be sure. Any help is appreciated. Thanks!

[Xringshooter]

It's just a spent primer casing, empty because the anvil has fallen out. If it was a used gun that you bought, the previous owner may have been shooting some reloads. The primer pocket was probably a bit enlarged from repeated firing and reloading and the primer was forced out by some back pressure coming through the primer flash hole.

[thebearpack]

Thanks Xring. I sorta figured but with this being my first AR excursion and everything about Colts seemingly being different I wasn't sure. Plus the detent pin ft into the indention (which I now know is from the firing pin) so figured I'd better double check.