I built a 6.5 STW which is the same as 6.5 300 Weatherby. I built it on a 300 Wby. MK V with a 30" Lilja 1/8 twist 140 gr with 82grs. H870 @ 3550 fps. I don't think I will live long enough to burn it out, at age 83 HaHa. If you want t reach out for a LONG LONG shot it will do it. Have fun...