Several thoughts, 1 have you loaded ammo in this die set/press before? 2 possibly not belling the case neck enough, 3 case mouths out of square,4 bullets too large in diameter in relation to case neck expander. I once go a Lyman die set for .375 H&H that wouldn't seat a bullet straight no matter what. I finally took the seat die apart, and you can visibly see the seater punch hole was drilled out of line with the rest of the die. If you have used these dies on your press sucessfully before, you can throw out this idea. Not belling the case enough can cause one edge of the bullet to tip on seating, and I once got a batch of .22 Hornet brass that had case necks so out of square that it was impossible to seat bullets straight. In loading some 32-20's recently, I tried using .314" bullets, and got a bad, off sided bulge in the case neck. I bought a .312" sizer for the bullets, and the bulge went away. As far as shooting them, if they chamber, I would, especially if this is a newer Marlin. Good luck
