SAMMI spec is about the same for COAL. So, your magazine should be fine.
284 Win is often used for f-class. So, I would think it'd be a good choice for long range targets and mid range hunting.
Pros -
good bullet selection
good barrel life
accurate
mild recoil
Cons -
lower MV than other 7mm's
no lapua brass
Not sure why 22 MOA matters. Mount a 20 MOA rail with good glass and you'll have no problems getting to 1k.
3100fps sounds overly optimistic. If that's important, you might want to look at the 7mm SAUM or 7 WSM. But, you'll have to open up the bolt face. And, you'll probably need to single feed or go to a long action. That's especially true if you go to the big 7's.
A lot depends on whether you're using it for recreational targets, competition, or hunting.
-- richard