I seem to one of the few here with a custom .284 on a S/A 700 (3.1" box) that has no regrets about it and would do it again. Most here seem to advise against it and it's true there are some good other alternatives out there. However, I'm very happy with mine. It's very light at 6.25 lbs with a Z3 on board. I can load to an OAL of 2.95" and even with the l-o-n-g TTSXs I can fling the 140 to 3050 and the 150 to 2950 with R17 without straining. It is very accurate and I've taken a whitetail at 500 yards with it and other game much closer in.
I originally planned on the 7 SAUM but the gunsmith balked claiming feeding problems with it but he was enthused about the 284; this may have just been his bias; I don't know. And, actually, with as light as it is, I really don't need much more recoil. But the 260, 7mm-08, 7 SAUM, 6.5 SAUM all would deserve a look-see I'd think. A lot of good bullets for this group.
Edited to add: I'd have no reservations about using it on elk with either of those two bullets mentioned or some others. In fact, I built it as fitting my concept of a mountain rifle; the thing is, mountain rifles work well most other places too.
Last edited by George_De_Vries_3rd; 11/15/15.