I would suspect much of your trigger problem to be in the stock fit.  Tricky little things, the amount of wood just ahead of the trigger slot controls overtravel.  If there's just a hair too much wood there, you get a trigger that don't go, or requires a gorilla trigger finger to get it to go.  Paul ran into the problem with epoxy from his stock repair.  I've also had to rebuild the area where someone removed wood on one of my stocks.  The trigger didn't stop until it got to the back of the guard.

There are sometimes other factors at play into SEE.  A rough throat for example.  Ask Bob S. about his 4895 reduced load for his 6mm Lee.  Rough throat+heavy jacketed bullet-the gas needed to quickly get past that rough spot = higher than anticipated pressure as the bullet momentarily stops or slows.  Swedish mausers often get hit with this "take it easy on the old girl" recipe with a big boom being the result.