I just bought some IMR-7977 to try in my 270WSM and my 7mmRem Mag. I just got it in today and I am ready to start loading some rounds for my 270 WSM. It looks like IMR-7977 should do well in a 270 Win.. I will also give it a try in the near future.
I just tested some 7977 in my 300. 210 gr berger VLD hunting bullets and to be honest I think there are better powders out there. MagPro and 7828ssc seem to work really good for me. I get single digit ES's with 7828ssc. I'm getting .25 to .4 MOA @100yds depending on the wind and of course me.
The MagPro has ES's at around 20 fps. Good groups usually @ around 1/2 to 3/4 MOA. With either powder I'm shooting at about 2900 fps.
The 7977 gave me about the same ES as the MagPro but the groups were around 1.25 MOA. I started the loads at around 2750 fps and went up from there to about 3000 fps. No change in groups at any velocity.
The gun I'm shooting is a Remington 700 action and 26" bbl 1-10 twist
I have tried H1000, Ramshot and Reloader 25. Also great powders.
Last week i did load development with a savage 300 mag, 26 inch bbl. IMR 7797. Velocity wasn't stellar. 180 grain SST's. (never made it to 3000 FPS even at max) accuracy was MOA at 100, we never did stretch it out.
It looks to be a good mild load, but IMR4350 yields much more velocity and consistent accuracy in this rifle.
No I have not because I loaned my 7mm Mag to a (friend?) and he has not returned it.
I did some shooting with my 270 WSM. I did not chronograph the loads so I don't know the velocity but I got a fair group with 69 grains and 140 Accubonds. I loaded some more and I will try them again with a different COL.