Years ago before I know any better I pulled the magazine guts from a pre 64 257 Roberts so it could be loaded to 3" OAL. I loaded it with bullets from 87 to 120 gr and mostly used it on New England woodchucks, crows and foxes when offered up.
It always shot well and even though the cartridge was short for the magazine,function was always perfect.
What I'm getting at is that Matt could do the 260, seat bullets as far out as he liked and the fit will be fine. Might have to check feeding as the rails on pre 64 308 actions are NOT exactly the same as those on the 30/06 actions. I found this out the hard way converting a 308 action to 270 one time.
That said I bet the 260 would work OK.
I just did something similar in 6.5 Creedmoor on a short Rem 700,25" #3 fluted SS Benchmark,bedded by Alex Sitman in an Echols Shrike, Edge fill, with Sunny Hill BM. Alex finished it up this week. I should see it soon.
Guess I built it with the same intent as Matt. Sounds like a fun rifle.
