I have a T3 .300 WM
Great rifles.
Mine wears a Sako Hunter pattern Mcmillan, and a fixed 10X SWFA MIL/MIL.
It shoots pretty good with 165 grain Sierra HPBT GKs. Normally I would not bother with that projectile in a .300, due to its poor BC, but it has proven to do well out to the mid ranges. In fact here is a group I fired on a rock, after confirming dope on some steel a bit closer. The rock was a shade past 600. The group was a bit under 3"s for 3 shots.
I no way shape or form will I say it will do it "every time", as that is a sub .5 MOA group, but the load has shown to average around 3/4 MOA.
In this pic, you can see the 600+ yard rock formation above and to the left of the rifle.
IN regards to the SWFA.
I am a big proponent of high quality optics, and am a Nightforce fan. That said, this SWFA tracks well, is clear, repeatable, and in 2 seasons of elk hunting (and 2 cow elk), along with shooting in the off season, I will say that I am impressed with the SWFA.