I've got a Mossberg 510 D in 338WinMag.
It has been a good rifle for me.
Only complaint is the "safety on" on this particular model doesNOT lock down the bolt handle, cost me an elk once....
As I peeled the slung rifle off of my shoulder with a back pack on, the bolt handle caught a pack strap and shifted half way up. When I pulled the trigger, all it made was a "clunk" sound.... no fire. All the energy in the firing pin went to slapping the bolt handle back down instead of striking the primer with the necessary "snap". I never let that happen again, killled lots, and lots of game with that rifle. Always had to baby sit that bolt handle though.

Ammo? Each rifle individually is different, you will have to experiment.