Re: 6.5-06 Ack Imp with new powders
I've used a bit of Retumbo, and have shot more sub .75" with it than any other powder. It seems to shoot best with one of the hotter primers, and the extreme-spread seems good, prolly because the case is almost full. I have used 60.5-61.5gr to get about 3250fps, which seems to be where one of the nodes is on my rifle. That's the velocity range I wanted, so I haven't pushed much higher. That's with the Hornady 123gr A-Max.
The 140gr A-Max will do about 2950-3000fps with 57gr of Retumbo. You'll want more, so these loads should be a good starting spot.
The case-capacity on my "Special" is 69gr of H2O filled to the mouth.
I hadn't thought about VVN165, so I am loading some now to be taken out tomorrow morning, and the next time out. Thanx, Seymour Fish, I'll let you know.
IMR 7977 seems to be all right as I've gotten about 3050fps with 56.5 gr, and groups in the .75" range. As I go up from there, the groups spread a little more, and that's the speed-range with 140gr that I am seeking, so I've stopped.
The accuracy seems better with hotter primers like CCI 250s and Winchester WLRMs, but standard primers work fine, but need .3-.7gr more powder to get the velocity back up where the others are.
IMR 4831sc seems to give lower velocities and bigger extreme-spreads, prolly because it doesn't fill the case enough. I've used 52.5gr to get 2875fps average with the 140gr Hornady bullets. Loading up from there may be the answer, but I am working more with the slower powders.
I am using the A-Max bullets in 123gr and 140gr weights because the accuracy is superior in my rifle to the target-grade hollowpoints made by Sierra, Berger, Nosler, Prvi Partisan, and Lapua, or Norma. It MAY be because my twist is not enough, but it may also be that I haven't run my velocity high enough!
My original plan was for this velocity, but in a 6.5x57 Imp barrel, as most of my competition uses a.260 Rem, or 6.5x55 or AI built on custom guns. Most of their guns are Savages or Remington 700s, so they have custom throats.
Most of the targets are under 2MOA, so the scores haven't been running away.
If you want, I'll be back to talk more about the tests I've run.
Right now I've gotta go to get ready to try some things out in the morning.
Have fun,
Gene