Sigh..Safe to say that's not a BR. Don't know what the hell it is. Look at the ammo counter, the bullets are pretty big, it holds less shots? Maybe they're bringing back single-fire to please all the Halo 1 fans.
I like the needle weapon, it's out of the box of the normal stuff. The ammo counter's making it look like some sort of slow-firing type of weapon. Judging from the crosshair I'd say a long-range weapon?
The guy who took the pics and posted them on MLG forums, says that it holds 12 shots per magazine, and fires one shot at time, but has a longer range than the battle rifle. The needler\carbine thing fires needles (obviously), and causes a superdetonation when 3 needles contact a target. With only 3 needles requireing an explosion, it most definately fires slower than the normal needler, or the carbine for that matter.