I couldn't get enough MR-2000 in the case to get 2600fps. 26gr shot pretty decent though @ ~2550fps.
I've been shooting 23.5gr Tac for the last shooting season with excelent results in a wild chambered Brux barrel. Prone with a sling put 20-rounds inside a MR X-ring for me Saturday, 16 of them touching (yeah, it had me grinning). I'm thinking I'm going to try them at 600yds in practice tomorrow. Have yet to have temp issues this time but had some a while back with Tac.
By far, the most accurate powder that I've shot is the IMR 8208 but I had short-stroking issues in 2-different rifles with this powder so went back to Varget, H-4895 and now to Tac and no more short-stroking issues. I know of others that shoot it without the issues so YMMV.
H-4895 & IMR-4895 are very good powders, meters well and both produce excelent accuracy, IMR-4320 is usually overlooked but it works great also, short-cut and small diameter so it meters well.
I shoot in the South so temp-stability is a big issue for me. I've shot with some that were shooting AA2520 with good effect who did good 1 weekend and were popping primers with the same load on the next, same goes with BLC-2 and WW748.
I'd sure like to find another 8-lb jug of Tac right now.