h50 bmg is what I'm using with a 175 eld-x in my 7rum. She's an 8" twist Brux with a short throat though... I suspect a bit more cowbell in a longer throat would be the same.
If you want to run 140's I suggest rl25, but 175-180 needs (preferably stick- ball might work too in a pinch) 50 cal powder... I've fried a couple pipes coming to that conclusion. I've given up on h1000 for anything more overbore than a 300win. Retumbo kinda worked with 160-168 grain pills in my last barrel, but I wasn't happy with retumbo in this barrel. If you can't get to pressure with the case 90% full or better, you will have consistency issues in a 7rum.
As far as vel., I'm idling my rifle and getting 2900 fps. I'd guess 3100 is on tap here as usual for a 7rum and a 175-180.