Need help with Mini-14 disassembly/reassembly

[Han-Tyumi]

I was using the RugerFirearms youtube video for Mini-14 disassembly. When I took off the plate, this little brass 'button' looking piece fell out with the bolt catch. The piece is not a perfect circle, more like an oval or a rounded rectangle. I do not see it in any disassembly video. I'm not sure where it came from or where I need to put it back to. If anybody knows the solution that'd be much appreciated, thanks!
serial number 195-83783

 

[Sugar River]

Looks like a spent primer........but how it got there is anybody's guess.

 

[pyth0n]

A Sugar River said, it's a spent primer. So it's not a part of the gun. On mine, a 183-, when the bolt is full aft, it uncovers an opening (the right side in your pic) that goes through & is covered by the side plate you removed. That's the way the primer got under the plate.

 

[daveag.]

I have those little "brass buttons" around my reloading bench.

 

[arfmel]

Yeah, a primer popped out of a cartridge case when the gun was fired, and somehow got through the little hole in the receiver to get behind the plate. The odds of that ever happening again seem pretty slim.

 

[Han-Tyumi]

Thanks for the responses everyone! For a little while the bolt was a little sticky and at one point even got stuck shut. I chalked it up to the gun just being very dry, but perhaps this played a role in it.