Alrighty after looking at all the deferent ammo I bought XM855LC green tip 62gr. Shoots fine and seems to hit extremely hard. What I was wondering what's the deference in the M855 , XL193, and M193? I'm not sure if there is any more reference. Those are the one I've came across so far. I'm looking for some good SHTF ammo to stock up on. I bought the XM855 because it was a good deal at my local Gander Mountain 420 rnds 140$. Is there any better ammo 5.56 caliber specifically? I have a 1-7 twist and that is why I went with 62 gr. I just got the gun last month and today is the first time I shot it. So this is the only ammo I have experience with. Any help with experience to save me from having to just try all the others.