Yep, definately compressed. Retumbo is really not a great powder for the WSM line, as I found out with 300WSM. It is rather large for its weight. RL22 would suit your needs alot more. Or even 4831sc.

You can get a longer drop tube to help settle it down some. Believe it or not, you can fit an extra 2 gr in sometimes.

I know I used Retumbo for RUM and it was such a slow powder, I had to put 102gr in to reach the velocity of a 96gr RL25 load. And RL25 is very slow.