Today I ran the Cayuga 151s in the 7PRC (22" Proof 1:8 barrel) , with a now functioning CED M2 Chrony. Because I haven't shot any solids this light in the 7PRC, I started with N565 at 70gr. Wasted some projectiles on the low end, but hey, it's all shootin' fun. Got to it late because I had to get a hay field tedded, so I had the sun in my eyes on my range.
I started with a COAL of 3.1900" I suspect more jump would improve things. I used WRE LR primers. FYI, they are tight in even 5x fired Peterson pockets! I'll try magnum primers of different flavors later.
The numbers:
70gr. - 2894fps
70.5 - 2935
71 - 2943
71.5 - 2949
72 - 2970
72.5 - 3009
72.8 - 3021
The group measured 1.20" at 100yds, and shots 5 & 6 are close. #7 went flying. Those charge weights - 71.5-72gr. - may call for more experimentation, although I'd like to get more velocity. I can probably push it to 73.5 gr. and see how they fall in the group. I'm not leaving any N565 on the table, so it's not too slow. If not, I'll switch to a slightly faster powder such as H4831sc. Tomorrow I have to bale, so iffen I don't get out and shoot before I rake, I'll shoot Friday.