BML:
I'm using a Bartlein in my .260 improved. It's a 1:8.5" twist....31" finished length. I'm getting very similar velocites with it when compared to the 6.5-284. This thing just loves 140's. I would say....ditch the factory tube and buy one from one of the reputable manufacturers...you won't be disappointed!
Good Luck,
Wayne
I went with a Bartlein on my 6.5x284. It is a Gain Twist barrel, 24" long. Starts at 8.5 and ends at 8 at the muzzle. It is the 5R style rifling. Plan is 140 Berger VLD.
I would use ANY of the following with confidence so it's really just a matter of cost to you and how soon you want the barrel:
Krieger, Bartlein, Obermyer, Hart, Broughton, Lilja, Shilen.