Your thinking is correct on the long action. I had a 25/284 and it really was too long on a Rem Short action.
If you go over on the accurateshooter.com forum, there are lot of people shooting this case in competition, 1000 yd.
There is only 6oz difference between a Rem long and short action.
For your information, my stock rem 700 with a 26" ss barrel is shooting the 162 SST at 3100 in tiny groups with Retumbo(215's), bullet jammed the lands. THis gun is a parts gun, bought the barrel off of ebay, Boyd's laminate, which makes it a poor mans custom junk yard dog. IT shoots 2 1/2" groups at 550 yards, so I will keep it.
Also, on your 24" Rem Varmint barrel, you would end up about the same weight if you got a #5 Shilen taper on a 28" barrel. The #5 Shilen will give you all the stiffness you need for your desired accuracy.
I put muzzle breaks on everything from 223 on up and wear electronic ear muffs.
