The only powder I've ever used for the 7 mm Mag is H-4831.
It provodes good accuracy, so I never had the urge to test any other powder.
63.5 gns of the H-4831, with 150 gn Partitions and Fed 210M primers. I haven't tested this load with Mag primers, and I have no ignition problems during November Deer season up here.
The above load delivers 3 shot, 1/2" groups at 100 yards with the adjustable scope set at 12x, so I have no reason to try Mag primers.
