You may have to bell the mouth of the case a bit more. I had the same problem with cast bullets in the 444 Marlin, another straight case cartridge, and thought I had belled the case mouth enough - truth is I needed more of a bell and once i did that the problems I had of shaving lead - even off gas checked bullets - disappeared.
Also, you will find your accuracy improves when you don't shave lead when you seat the bullets. If you are concerned about too much bell, you should look for split cases at the mouth. If they don't split you are still good to go. You may have to turn your seating stem way down to get the bullet properly seated to your desired depth before trying to take the bell out of the case mouth. Then, if you do not have a taper crimp die you may wish to use your sizing die (without the decapping pin in it) to taper crimp or just further reduce the case mouth bell . I did that with my 444s as I was afraid I had too much bell on the case mouth to move the case into the seating die without catching the case mouth on the edge of the seating die and crush the case. After the initial seating either use a taper crimp die or your sizing die and you should get a uniform crimp with every case, and enhanced accuracy and powder detonation as well. HTH. Mikey.