Re: Accuracy International stock on a 300 RUM
The problem with the Remington Ultramags in the AICS magazines is the length of the rim to the shoulder. The two deeply stamped strengthening ribs in the magazine body are placed too far back for the Ultramag brass to fit. The .300 Ultramag is 2.387" from rim to shoulder. The .338 Ultramag is 2.296" from rim to shoulder. The .338 Lapua is 2.161" and the .300 Win Mag is 2.196" from rim to shoulder. That's the reason why neither the Lapua or Win Mag AICS magazines will work with Ultramag brass without modification. One solution is to remove the strengthening ribs via grinding or machining. The magazines then have an open slot machined in them that exposes the cartridges,follower and spring to foreign material. People have done the modification,but they have to come up with some way to cover up the slots.
It has been done successfully with the use of the .338 Lapua magazine, the front ribs have to be machined out to allow for the RUM's extra shoulder requirements. This will allow the .300 and .338 RUMS's to function with x5rds very successfully. Of course, once this modification has been done, it will void any warranty/repair/replacement with AI on that particular magazine.