3.650" magasin box is long enough.

Base and shoulder diameter is some what larger than the RUM's, which I know M1999 work fin with (with the original "ultra" follower).

8.59 Titan --> base 0.581" - shoulder 0.563"
338 RUM --> base 0.551" - shoulder 0.527"

You would also have feed rail and magazine work to deal with I would suspect. I'm pretty sure that MRC is going to come out with an action more suitable to this size cartridge. I think it would be time well spent on the wait. Just my.02

Shawn

Tomjac,

The M99 action comes from MRC set up for .30-'06 or .375 H&H head size cartridges. Apparently there is no source for bottom metal suitable for cartridges derived from larger diameter cases. Ray A. gave up on his .404 Jeff/M99 project because of this he has posted here.

MRC has their "PH" action in development, and that one is intended for .416 Rigby and other large cases.

jim dodd