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.
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...