Thanks to Dober and Bob, I played with the 7 Mashburn a little and it helped develop my new wildcat 7mm. There were a couple things I didn't like about a straight 7/300WM, mainly the short neck. A RUM case gave to much case capacity and wouldn't work well with "extreme" powders, 375 Ruger case was a pain to neck and form.
I found that there was a fairly common relationship between neck length, bullet diameter and shoulder angle on the recent "accuracy" cartridges. I new what the Mashburn and 7 Rem Mag would run for velocity when I changed the throat angle and length for the VLD bullets. So I applied all this info to my design based on the readily available 300WM case. The design gives a few grains capacity over the Mashburn, and like the Mashburn, is very forgiving to load for. The result was, a 180 Berger at 3200fps in a 27" barrel. So far the test batch of brass has been loaded 9 times and the primer pockets are still tight. Now I can put the "real" rifle together with our new stock design and continue "testing" during hunting season!
Do I think its better than a Mashburn? Still torn on that one. The Mashburn has history, nostalgia, and panache. This is just another option that gives a little boost. I will continue to build both!
Here are some pics of the 7mm Rogue on the left vs a 7 Rem Mag on the right.