In my PGW Timberwolf 26" barrel the best results are with H1000. I did a full load development with H1000 and Retumbo, but could not get the Retumbo to group quite as well. It was still good (1/2 MOA at 200 yds), but the H1000 was definitely better.
These were 300SMK at 2780-2800.
Powder was 92.0 for H1000, and 92.3 for Retumbo. I know a lot of people on this site say 94g of Retumbo, but I get pressure signs after 92. BTW I seat touching the rifling. Backing away even a few thou takes away a lot of accuracy.