https://thegreatmodel8.net/

I finally got the 81 to the range. Noticed it was doublefeeding. (Unfortunately it did not dawn on me to take pics). On the 2nd or 3rd round in the magazine, the bottom of the bolt appears to grip into the side of the casing on the next round (causing marring on the casing) while loading the previous, and drag it partially out of the magazine, jamming the weapon. After pulling out the partially loaded round and shoving it back down in the mag, it runs fine for the last few shots. Previously I had a loose barrel nut which I tightened to the best of my abilities without the tool. I don't know if I was able to tighten it all the way, but I kept an eye on it and it did not loosen up. I was using 200gr factory .35 Rem. Remington brand.

Sounds like the magazine lips need to be reshaped . If they are to wide the rounds will not stop at the top of the magazine when firing. There is a "sweet spot" the lips must be shaped - front and back, differences are almost unnoticeable. The follower will push the cartridge to high and double feed as the " lips" let it rise too high under recoil.