So if one had a mkv 6.5 creed on a 6lug, could one simply rebarrel it to a 6.5 rpm? One size action ala Tikka?

Most likely can be done but given the huge difference in case sizes I’d bet the feed rails would need to be worked over. If I wanted to do it I’d ask Weatherby and see what they say.

Meaure the magazine box , if it is longer then 3.00 inches it can be done.

Agree with John55 on the feed rails, and add that a new magazine follower may be needed.

The SAAMI max length is 3.34" so you would want at least that much mag length.

I don't think you have to rebarrel. The 6.5 RPM reamer would clean up the Creedmoor chamber. No problem.

I converted the "ala Tikka" superlight in the creedmore to the rpm for around $425 (?)....shot factory 140 a.b.'s over stated velocity into sub 1/2 on the first outing...........when they offer it in a vanguard, it will get noticed !
Some what related : Heard they were gonna put out a .338 rpm........fun !