If you need that extra .040 of an inch in the magazines and just can't seat bullets deep enough you need one of the gunsmiths most used tools, the Nicolson Mill. Make sure you apply plenty of grease, elbow grease tha tis.
A Nicolson mill of course is a file. File .020 out of each end of the magazine box. Assemble the rifle and make sure the front wall of the mag box isn't under cutting the feed ramp. If it is, file it flush with the box. You need a dummy round to do test and try your. Seat a bullet in a case to the maximum length you will use. Run the cartridge up and down the inside of the mag box while turning it at various angles to see if it will hang up.
There might be one thing to do that will be simplier. Measure the box before you do anything. Factory specs and reality are often .040 or more apart. the box may not need any work at all.
