They looked alot like M60 M13 links, they had the little dogleg at the end that clipped into the roundsrim to hold it into place. Were these made for the 50cal tank gun? I know that it was radically differant from the M2.
BrenLover

BTT

They are from the 50 cal. that is on the Bradley and in the Abrams tank.  It is a high rate of fire gun and strips the round differently than the M2. I think it is called an ANM-2 or something.  

Those links are almost certainly for the M85 machine gun. Just like giant M60 links, intended for push-through feeding.

The M85 was experimentally made in ground versions, but its primary use was in tanks. I think it was mainly used in the older M60 tanks, in the commander's cupola. The advantages of the M85 were in its shorter receiver and dual rates of fire. It had a higher rate supposedly for engaging aircraft, and a slow rate for ground use. The M85's had shorter barrels than M2's, and snazzy-looking flash suppressors. They fired from an open bolt, and locked by means of a couple wings or flaps on the bolt that spread apart into recesses in the barrel extension. I was a small arms repairer in the Army back in the 1980's, and remember the M85 was the most dreaded weapon at the Aberdeen training school because it had so many parts. Much of the extra complexity was due to the time delay mechanism for the low firing rate. We had to be able to assemble one from jumbled parts without referring to a manual to pass the class. I liked the design myself, but apparently it was not too successful in service, as I believe one of the design requirements of the newer M1 Abrams tank was that it have enough room inside to take the M2 machine gun, or one of its variants. I never got to see for myself how the M85 worked out in the field, as I was not assigned to any armored units.

I don't recall that the Bradley used a .50 of any sort. The main gun is the 25mm "chain gun" and there maybe was a 7.62mm M240 or something for light work. Plus TOW missiles and the 5.56mm side weapons.