Regarding the Brownell's .308 mags. I just got two. Glad I did not order any more. The followers stick badly but were much better after I ran a cloth coated with CLP through them. With .338 Federal rounds they seem to feed OK most of the time, but the internal length must be short because rounds that work perfectly in the DPMS mags hang up in the Brownells fairly often. In my wildcats, the .358 HDH, .500 Phantom, and .470 Rhino, forgetaboutit. They nose dive on every round and the solid back of the feed lips does not allow much tweaking. And with the .358 HDH the mag swells so badly after 3 or 4 rounds are inserted that the mag will not even enter the magazine well on both Tactical Machine and DPMS lowers. If you are using them in .308 based rounds they will likely be OK once they get broken in but I don't like having to oil the insides of the mags to make them work. Plus, pulling the follower after a few cycles and you can see multiple places on the follower where it is dragging on the magazine body. Again, once the followers wear it they should be OK but what a PITA until then.
Can't say I am a fan so I will be sticking with the easily tweaked DPMS mags for my wildcats but at least I have a couple more mags for the .338 Federal, if I seat the bullets deeper.