Would skip the 7mm mag or 300wm.

7mm I would go for a 284 or a 7mm WSM

Or I would build a 6.5x55 swede on a long action.
6.5x55 lapua brass is $0.75 per which is decent for lapua brass.

I personally set up a 223 7 twist because I like underdogs but havent gotten a chance to stretch its legs.

Last 223 7 twist I had would shoot 90 gr bergers at 1/4" at 100 yards.

6mmBR is nice too. Mine was nothing special and it took me about 30 rounds to find the right load.
3/4" at 300 yards, better for 600 yards but not quite enough umph for 1K but it would work and literally no recoil.