Seafire, don't feel bad, my first deer w/338/06 was in the woods from a stand I never had been in before that dawn, at sun up shot a 55lb deer, around 40 yds thru the chest, it ran about 100 yds also, passing by my stand where I could see the silver dollar sized hole and blood pumping. The 200 BT sailed thru both lungs. Later a nice 8pt. at 200 dropped DRT and a very nice 6pt WT dropped in about 3 'death lunges' so perhaps those little deer are not big enough for the larger 'cone shape' energy dispersion? Who knows. I truly felt later I would have been better off had I taken my then 6mm TCU Carbine loaded w/85 SGK HPs where energy transmission would have been quicker in the short wound channel.
I had really thought I was shooting a doe about twice the size and distance or I would have passed on the deer, but odd things do happen afield, as again, never had hunted in that area nor stand and at early legal light, range estimation and body size was off.
As to ROT, I have a Sako 75 GW for my son, it has put 2 out of 3 into the SAME hole at 200 yds w/130 ABs. Twice the same day! And I do mean the Same hole, first and second shot both times, thanks to a 6.5-20x for testing. Federal brass did it (one group 308 stamp, other 7/08), RP would not duplicate.
Did I get lucky? I think not. The 75s have 9" ROT in 260 and mine shoots fine inc. 140 amax, bergers, RP CLs, and 142 SMKs that I tested FWIW.
Now I do have to temper that info, with my first quasi '260', a 6.5-308 Win that was a 23" 9 ROT, mistakenly bbl'd as I had ordered an 8t. That rifle came in just months prior to Rem 260 intro, but I compared blueprints on the round thanks to the Lonoke, AR plant folks, to my champer reamer spec and concluded I could use factory ammo. It worked/fired fine, no problems, but key holes and patterns resulted, no tight groups. I tried 140 PTs in that rifle also w/no success. That was a custom bbl that shot respectable groups using 100 Sierras, 129 SPs, and 100 NBTs.
If building a 6.5mm, IMHO an 8 is the way to go, some use 8.5s and if a longer bbl 260, 6.5 CM, or 6.5x47 L I can understand, as a 6.5x284 or 264 WM to keep pressures down. At the same time, I would not 'count out' a 9 ROT 260 to shoot well until tried. My experience varied. I would think perhaps the 130 Berger might prefer the 8 or 8.5t as the 140 NAB, but the 130 NABs again shot fine in my boy's 9 so you just have to try each rifle to see what they like.
I do seem to recall two M7s, one an 18.5" blue, the other a 20" SS, did not like anything heavier than a 129 SP, and both sported 9t.
Just wanted to pass on my results. Greg, if your 1885 was tested with 130s I wonder if it was ABs or Bergers? Some say they had a 9t, but I could have sworn long ago I read in Browning Literature/catalog they came in 10t and if printed, may have been a mis-print/typo, or perhaps my mind is failing, I don't know. One thing to consider on twist, there are many variables, inc. the 'advertised ROT' vs. the 'actual ROT' which sometimes varies. Likely not much, but perhaps enough to matter. I do agree that given a choice, I prefer an 8t everytime with both 6mm and 6.5mms, as I do a 9t w/7mms.
