Agree with downwindtracker. My many 6.5/55's, all 1 in 7.9" twists, top out at 2600-2675 fps speeds. This with 140's, R22 in 23.5" military barrels. Bores slug at .265-.266", which may well contribute, along with the quick twist, to the rather slow speeds. Fast twists seem to 'hit the wall' more suddenly at a prudent max. They get a little touchy and inconsistent, pressure signs vary somewhat shot to shot (case head expansion). Temp. sensistive too. Drop a half grain and all is well pressure wise. And hopefully still within your accuracy node, as it seems most 6.5's shoot their best loaded rather warm.
The only 6.5/06 in my life, a montana rifleman 1 in 8.5" twist 24" barrel that slugs at .264" is built on a F.N. supreme action. A sub 1/2 moa shooter in its prime, somewhat less now with 1000 rounds down the pipe. This cartridge buys you a couple hundred fps over 6.5/55 at a cost of half the barrel life. Downrange performance is however impressive. IMO its a hunters cartridge.Carried a lot and shot little. Fiddling around trying to fine tune accuracy was a mistake for me. I shoot long range steel, but not for long with this one once the load developement was sorted to my unrealistic standards.
Being a wildcat, chambers vary. One must start conservatively. Not much modern data out there either. I used nosler #3 (1989) data and it proved out pretty close. Had I of used some of the older data that I found , those starting loads would have for sure stuck the bolt or worse. 51.5gr of R22 with lapua 139gr scenars 215m in necked lapua 30/06 brass is where this one found home. High 2800's. Tryed 139scenar, 140amax, 142mk with h4350, h4831, h1000, retumbo, R22, and R25. If speed is your thing then R25 and retumbo will produce. YMMV but approaching 6.5/06 max for me was somewhat touchy. 3 or 4 shots at warm normal pressure then one all flattened out with a loose primer pocket and well outside of the group. All charges were weighed on both the scale and balance beam. Seated .040" off in a long throat. Who knows?.
40 years with the 6.5's has taught that they all like their bullets to be seated nice and straight. 3 thou. or less runout measured at the ogive works well. Nice round groups result at long range and no fliers (wind effects excepted).To get there I use lee collet sizer and redding benchrest seater dies. No need to measure every round any more with this kit.
Bottom line is that 6.5mm shines because of the bullets. Loaded straight at over 2600 fps and you will be smiling.
