I've been working up a load for my remington 700 in 7mag. Mine has a 26" barrel. I started with RL19 and Retumbo powder and 168 berger vld hunting bullets. I made up 40 rounds total. I did 5 shot groups at .005, .010, .015, and .020 off the lands with each powder. I don't remember what the initial powder charge was for the RL19 but it was a safe load. The Retumbo I ended up loading @ 69 grains even.
Out of these 8 loads, I had 2 groups that were around 1" @ 100 yards and I had 1 group that was a little over .6" @ 100 yards. The group that shot the .6" was loaded with retumbo @ .015" off the lands. The only problem i had was that my case necks were dirty as hell so I assumed that was a sign of low pressure. I went back to my reloading bench and began to work my Retumbo loads up. I loaded up another 33 rounds @ .015" off the lands (11-3 shot groups) slowly working my powder up to max load. I went back and tested my groups again and was able to get one of the batches to land at .367". Granted this is only a 3 shot group, but it will do for deer season this year.
My load this year will be 168 vld hunting bullets, norma brass, federal 215 Match primers, 71.8 grains of Retumbo loaded .015" off the lands, provided my next round of testing goes well. I've built a drop chart for it, now I need to go out and test it at a good distance so I can get a better velocity and then rebuild my drop chart again.
With all this being said, as I'm sure you already know, every gun is different. The only way to really know what load your gun likes is test, test, test.
