Len: This bbl was the first I had made in a series for the 7mm/.338 Lapua. It's a gain twist ending in 1:12 and it is 34" in length. The bbl I am using on the action right now is 28" and is a 1:9" twist. I haven't chrono'd the 162 or 168's in the 9 twist yet, though i'm sure I won't see the velocities I did with the big bbl! Case capacity is 116.3grs H20. Measuring method was to weigh the brass dry, add water, weigh case full, empty water, weigh water, and then weigh case. Water level was filled to where the edges of the miniscus were level with the top of the case. The load I used was at the borderline pressure ceiling, but I have used up to 109.5grs. with the 162's. Never went that high with the 168's though. I posted some more info on the other forum where we were talking about this rifle. You may want to check them out. You still getting ready to build yourself one of these beasts? If you want to start from the "top down", this would be a good project for you!
I have used the A-Max's and the Berger 180's in hunting loads. Both are great, but the A-Max's seem to come apart on occasion. Not being a big fan of Bergers, I have probably used the A-Max to take at least 4 deer that I can think of and 1 elk. As far as powder, for the STW, I would really consider the 872. It's a great slow burner and it's not quite as temp sensitive as the 870. Since Hodgdon no longer mfrs. 870, I would definitely go with 872 and work you a good load up. I have been using 108grs. 872 with the 162 A-Max and the 168 SMK with excellent results. I'm getting around 3540 with the 168's and an avg. of about 3594 with the 162's in my 7MM/.338 Lapua. ES is lowest with the 870, but the ES with the 872 is nothing to laugh at. Besides, the 870 seems to be MUCH more temp sensitive than the 872. Just my 2 cents! Good luck!