Back in '06 or '07, when I was wintering in Jefferson, Tx, I was up to Gander Mtn in Texarkana and they had several older Ruger rifles. They had a M-77 in .358 Win, .284 Win, and a couple of others.
I always lusted after both of the above. But they wanted something like $900-$1000, and I thought that was hi-way robbery.
but not long after I returned to MI, I made a trade for a flat bolt in .358 Win. Had I known that they were twisted 1~16", I'd never have lusted after it. Mine sprays a pattern with 250 gr. bullets. But will print 200 gr. just over an inch. (Which should be adequate for deer...) And I have other .358s that are twisted 1~12" anyway.
Congratulations on acquiring a nice rifle that Ruger should have made more of...
GH