What kind of mods need to be done to rework a 700 to be able to use the "full-length" Ultra Mag case in 338? The 338 RUM is quite a bit shorter than the 300.

Andy

If you already have the 300RUM, it's as easy as a rebarrel although you may want to add a Wyatt's box to increase length a tad to seat those looong 338 bullets.

I ran a reamer into a remington 338RUM barrel to use the longer 300RUM brass:

http://www.snipershide.com/for...wflat&Number=2933597

Pretty straight forward, you just need the reamer. Oh, and if you want to fit the longer cases with long pointy bullets in the magazine there will need to be some mods there too.

I ran a 338 Canadian Mag reamer into a Hart barrel with muzzle break on a 700 Rem 338 RUM. Sweet shooter. No magazine issues.

Also ran a 300 RUM reamer into a 700 Rem. 300 Win Mag. Had to open the width of the feed ramp and change follower and mag box. Works and feeds fine.

Never had the need to convert the 338 RUM to the EDGE, but having built a fair number of each, there is very little down range performance difference between the two. The benefit of the RUM is readily available ammo if something happens to your handloads. That said, they both use the 300 RUM mag box, so as far as I can tell, all that is needed to convert from one to the other is to run the reamer.

Per my data the net difference between the Edge and RUM loaded to the same OAL is .6grs of capacity.

With the same bullet and the same cartridge length the difference is more like 3 grains. If you also increase the cartridge length by 0.09" (which is about the difference in case lengths), then it's closer to 6 grains. It depends a bit on the density of the powder being used, but even so it's not a huge difference. The 300RUM brass seems to be much more available so would be a reason that the "wildcat" is preferred by hand loaders.