I recently purchased a new Rem.CDL in 7mm Rem. Mag. With the intentions of using it for a long range Deer/Antelope/Coyote rifle. I was wondering what all would be involved in making this rifle into a 7mm RUM? Can I get it reamed? or do I have to get it rebarelled? or will this action even accomaodate an ultra mag?
If not an ultra mag, could it be made into an STW?

Yes, you can simply rechamber to 7mm RUM. The magazine will likely only hold two rounds unless you modify it.

HOWEVER, it would typically be much cheaper (and quicker) to simply sell or trade your current rifle and buy the same in a 7mm RUM than to do the conversion work. In addition, a "factory" RUM would be more valuable than a "rechamberd" RUM if you should want to sell the rifle in the future.

Check your mag. length, but I agree w/ stonecreek, just get another rifle. The RUM is way overbore anyway. A better rechambering job would be the 7mm Dakota; same action/mag. length & feeding should not be a problem. There are no flys on the good loe 7RM either. Look @ your drop tables for say 150gr buulets, just noit that much diff. out to 400-450yds.

Thanx for your replies guys. Unfortunately, the reason I bought this current rifle, is because I am left handed, and in Canada its not that easy to find the stuff a guy wants!
I have read a fair bit on the Dakota rounds and agree, but I have heard some problems about Dakota brass, and that it isnt that great, seems to be too much variance between it and other makers of brass who chamber for them.
Also, if/when I do this future work to the rifle, it would only be when the bbl is gone, and its time for a new one!

The simplest solution is to simply rechamber to 7mmstw.The magazine and feed rails will not need any modification as they would with the 7mmultramag.The 7mmstw only gives up 50fps to 75fps to the 7mmultramag anyway.