LuvmyLRP,

I should also post this answer on my 12 FV .223 thread, but I'll answer your question one here on the 12 FV 6.5mm Creedmoor thread.
Actually, it is hard for me to believe 77 gr bullets will even stabilize in a 1:9 twist, too!
Everything I have heard for years and years says they won't, and even Sierra says they won't, but when I tried them, I was astounded by the results.
I never expected the 77 gr SMKs or the TMKs to group at all, and they wound out shooting better than any other bullets I have shot from 50 grains to 70 grains with this rifle.
The 69 SMKs and 69 TMKs shoot well in the 12 FV .223, but the 77 SMKs and TMKs shoot even better.

Since I started shooting 77 grain bullets, my overall average improved from 0.362 to 0.320.
My average with the 77 grain SMK and TMK bullets is 0.285.
I can't explain it, I can only report the results.

However, I expect it has a lot to do with loading the 77 gr bullets out to 0.020 off the lands.
The Sierra recommended seating depth for both bullets is 2.260.
I am shooting the SMKs at 2.290 to 2.303 and the TMKs at 2.325 to 2.345 to get the best results with my chamber depth.
The TMK tips make using O.A.L. a bit more complicated because the tip adds at least 0.050 to the O.A.L.
I questioned Savage about how they came up with the 2.260 recommendation and asked it the limits of an AR magazine had anything to do with it.
The response from their rep was that the AR mag limits probably had something to do with it.

The 77 SMKs averaged 0.395 when the O.A.L. was 2.280 or less.
The same powder and bullet averaged 0.251 when the O.A.L was between 2.296 and 2.301.
The 77 TMKs averaged 0.275 when the O.A.L. was between 2.330 and 2.345.
When I moved the 77 TMK O.A.L out 2.350 to 2.353, the O.A.L was 0.330.
When I moved the O.A.L. back to 2.293, the 77 TMKs averaged 0.289.

I think finding out where to seat them makes a difference but I honestly can't explain why they even stabilize.
It is pretty clear to me that with this particular rifle, the position of the bullets re the lands is pretty important.