MS,
Is 77gr mk262 going to shoot worth writing home about in a 1-9" barrel?
Some do, some don't.
MK262 is better suited for 8 twist and 7 twist.
The groups above were shot in a White Oak SPR gun I built for a guy. This was a test target before I shipped it off as I recall. Usually they shoot better once broken in. Plus handloads tailored will do better.
8 twist is what I would recommend for an all around . Not much an 8 twist won't shoot from 77s to 50s usually.
For 9 twist guns if you stick with 69 grain SMKs on the heavy end, will do great.
52 grain SMKs pushed by 25 grains H335 is a solid load to try for a 9 twist gun. Odds are it will shoot small groups if your gun is put together decently.
Cheers.