So, the Boyds "pepper laminate" stock I bought for a naked Mosin carbine action was a bit tight here and there. I picked up two different woodworking chisel sets from Harbor Freight, one for $5, one for $10.
One of the chisels had a 45 degree blade about 3/8" wide. That turned out to be the most useful tool. I used it like a knife, and the laminated wood cut smoothly. I had been afraid it would be notchy as the cut went across the plies and glue lines, but the laminate cut like ordinary wood. Actually, maybe better, since a long cut didn't try to follow the grain.
I got about halfway there, and then the rear sight turned into a problem. On the carbine the sight is on a band that wraps around the barrel instead of being dovetailed into the top. I'm replacing the sight with something else, so I have to make a tool to remove it before I can finish the inlet.