Yep, nice animals. Sometimes things do work out.
It's accurate enough not to mess with the load, although I'm sure if he played with it he would probably realize even better accuracy, as he hasn't played with it one bit.
That's the only powder and OAL combo he's tried.
I'd consider 3000 fps or a hair more his max load if he wants to get any reasonable brass life out of it. At a certain point the belt will keep on expanding a few ten thou per firing until it is just too tight. Usually they stabilize at .606 OD or so on the first to second firing. If they go .6065 on the next firing, then .607 on the next, usually they will keep going and hit .6075 then .608 and become too tight in just those one or two firings. Generally it's about 65,000 psi that this case is limited to or it just keeps on expanding at the belt. The problem is that you can not size the brass on the belt unless you make a special belt sizing die to use in the first stage. Most beltless cases will let you go to about 68-72,000 psi before experiencing short case life, and it's generally primer pockets that begin to open up rapidly.
I know he killed a mountain goat at 300 yards with it. Clean through, about 2" diameter exit hole, don't remember the details at this point.