I answered in the 2nd post but I'll do it again and elaborate here.
The shank O.D. of the Howa specs at 1.023"
The Weatherby is 1.060" (Old spec was 1.0625 or 1-1/16")
The Howa is a 1.5 MM Pitch or .059" per turn
The Weahterby is 16 TIP, or .0625" per turn.
So the Howa action has a Shank Well that is .038 smaller then the MK5 and the threads are off 31 ten-thousandths per revolution.
If your barrel turned into the receiver 13 turns it means the thread will be off a total of 49 thousandths. Far too much to work. The shank of the Howa is too small for the MK5 and the MK5 is too big for the Howa.
You could cut the shank off either barrel and re-shank and re thread to make either work in either action, but it's no different than starting with a contoured blank in labor. You would be ahead in the cost of the barrel however, if you already own the barrel. In either case you will loose about 3/4" to 7/8" of barrel length.
Winchester M70s have 16TPI like the Mk5 but the shank is longer, and only 1" in diameter not 1-1/6" like the MK5. So it would have to be cut off and re-shanked to work, which also means deepening the chamber when it's fitted. I have put M-70 barrels in to MK5s before.
Lastly I would point out the old "Varmintmaster MK5s has a totally different shank and thread, so if you have a 6 lug action it may be the same as the old Varmintmaster.
Those actions had a shank that was shorter buy .030 than the standard MK5, and were 7/8" in diameter with 18 TPI. So again both the regular HOWA or the regular MK5 could be machined to fit, but the work is the same as starting with a contoured blank but for the fact that the chamber would be about 95% done so it would only need a small amount of reaming.
Last edited by szihn; 03/21/17.
