1. My rifle is amazing. Has not jammed at all.
2. I got a field grade and with the exception of those two "stray" shots it gave a nice 4 inch grouping at 100 yards. I'm not even that good of a shot (at least according to the AF).
3. Unless you get a adjustable gas plug, commercial ammo will not work. Its too much powder and will damage the Op-rod. Hornady and Federal are the only two commercial manufacturers that make the M2 ball ammo that i know of.
4. I got a field grade because they did not have any service grades out when i went to the south store. They let me use one of their muzzle gauges and i found a diamond in the rough that was a 1. That particular rifle also had a great finish. The rack grades are usually ones that are pretty beat up, have a lot of wear and tear on them, and are usually bought for parts. The field grades like mine are in better shape but still show signs of use. The service grades have a lot less wear and have a new stock and handguard. The SG specials are even better and I believe are rebuilt.
If you are active duty then your mil id counts for all of the club and other affiliations needed. Although I picked it out at the store (which i would highly recommend if you can), i had it shipped to me because i saved about 50 dollars on tax. Get one, you won't be disappointed.