I found this advise in an older thread. I think crowbeaner wrote it. using it to work up my 1st batch of test loads. Right now here's what I got:Having spent the better 3/4 of my life shooting Remi Semi rifles, I can offer a bit of insight as to your problem. First is the already outlined cruddy chamber. that bent brush is neat; I use one myself.
Second is that semis are ammo sensitive- if the powder used in that particular ammo is too slow of burning rate, the case will not obturate and contract properly in the cruddy chamber. This causes the case to stick too tightly to the chamber walls and causes undo exertion on the bolt causing the tearing you describe.
Check for gunk alomg the frame rails where the action bars slide- clean them and use 1 drop of RemOil on the frame. Lube the gas pipe under the action spring with a shot of lithium grease after cleaning the rod- crud here can limit or slow the operation of the action.
Make sure the chamber is SHINY clean, and clean it after every 15 rounds or so to insure proper obturation and extraction.
Use MEDIUM burning rate powders in reloads- nothing faster than IMR 3031, and nothing slower than WW760/H414.
IMR 3031 for 110 to 125 grainers, WW748/ BLC2 for 150, WW760/H414 for 165s and 180s. IMR 4064 will work for 150s up.
My old 742 has one job- putting meat in the freezer, nothing more. I use other rifles and calibers for other shooting and hunting purposes. It does this job superbly. As long as the temperature is above -20 it never balks. The only rifle I would replace it with is a 760 or 700 in the same tired boring old 30/06 caliber.
Remember that most big game hunting is done with a maximum of stalking and a minmum of shooting; one to three shots from a cold barrel. Always foul the bore with at least 2 shots before hunting. Dry patch the bore once daily after shooting light is gone.