GETTING MY COLT 6721 UPPER FOR SALE TO WORK

I will attempt to search for some. The piston rings appear to be the bolt rings but at smaller. The outer diameter is about .375 of an inch plus the internal diameter about .310 of an inch.Perfectly, there is certainly 2 variants of the 6940P, as well as the one I had, I'm %ninety nine confident the rings within the piston had been just like the ri