I am working on one to be posted here, I told the admin I would have it three weeks ago, but with the kids and school starting for the kids and myself, it has been hectic. Mine is a 6.5-284 and in short it is the most accurate factory built rifle I have ever laid my hands on. I have had my hands on a lot of them. I have shot a lot of custom rifles
that don't shoot this well, and a few that did, fewer did better. I shot a 1.2 inch group the other day with ammo ranging from 2800-3200 FPS and 4 different bullets, and 3 powders, I was emptying spares that I had one or two left of each. To me given the differences in ammo, that is pretty impressive.
Basically like buying a box of rem, win, Hornady and Federal ammo and putting one of each in your magazine and firing a group, most rifles would be all over the paper, if all were on it.
Everything on it works advertised and it is easy to find a good load for at whatever velocity range or bullet you are looking for. There are some detractors who say it is not a true 26 inch barrel, and this is true, but it somehow matches velocities that target shooters get with 28 inch+ tubes. The brake works perfectly but you have to follow the instructions in the manual when cleaning to keep it from getting sticky. I see on average about 10-12 FPS lost from opening the brake. Hope this helps, I will have something more detailed up hopefully in a couple weeks. I have a few more things I need to verify before I send it to Mr. Backus and have to finish writing it which will be about an hour after I make sure everything is correct.
Not a 7 or 300 mag, but hope this is helpful info.