Re: M1 Garand question
gas guns need some special attention to bullet weights, too big can strain them; a box of ammo is not going to damage it most likely so I doubt you're in any trouble.
Lake City military ammo is king but also hard to aquire or too expensive for most folks.
If you are wanting to reload, I would suggest just getting your hands on some new brass, these things destroy brass and don't expect (or try) to reload shells coming out of this thing more than 3-4 times.
The brand of brass doesn't matter so much as your loading techniques, luckily '06 brass is extremely plenitful and common so you shouldn't have much trouble.
I know American Eagle has stuff for the .308 that is decent enough to get brass from but I think you're better off just buying new brass if you're wanting to reload.
"Loud noises don't end gunfights.... well placed shots do."