Not to be an annoying know-it-all or anything, but I'll shoot any rifle semi-auto against someone with the same rifle in the full-auto version, at 100-150 yards, using the silhouette military targets or even regular "bullseye" targets. I guarantee you that I will have a higher hit count than the full-auto operator, even if he sticks to the short burst doctrine. I recognize the value of full-auto burst fire for CQB, but at anything past 25-50 yards it's simply filling the air with lead and noise. Your first shot might connect at that range, but the subsequent ones are just going to deplete your ammo supply.
Now, a SAW or GPMG is a different story, but we're talking infantry rifle here, right?
Also, do all you groundpounders remember how fast a twenty- or thirty-round mag tends to go when shooting full-auto bursts, especially in the excitement of live fire or one of those MILES cowboy-and-indians blastfests?