Picking some brains here for my brother. He has a finish M39 Nagant and is experiencing heavy bolt lift after firing a round.

I'm a little short on specifics here myself, but here's what I know. M39 Nagant Finish in origin, shooting S&B factory ammo. Has about a box through it. Said the first round had a slightly stiff bolt lift then several that seemed just fine, then another with a heavy bolt lift and the last four rounds in the box had a heavy bolt lift after firing. The rifle doesn't appear to do if it you just dry fire the mechanism. He didn't bring the spent cases over so I'm not sure if there are any signs there that might help.

I'm trying to come up with a list of possible causes to help trouble shoot this situation. The 2 things that come to my mind right away are either bad headspace or lug set back. Could be overly hot factory rounds I suppose. I haven't been able to track down any Norma here locally yet to try in it. Any other thoughts or ideas??

The easier to check the better!

Thanks in advance for any and all advice!!

In a 91/30 with 180 gr and 50 gr IMR4895 I get heavy bolt lift.

S&B kicks about as hard.

S&B ammo is hot.

In an M39, I get heavy bolt lift all over the place, as the chamber is tight.