Quoted: Anybody have a link or can describe it? I am curious. How do they "pull" the next round in? how does the link get "de-linked"? etc
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I asssume this is a general question and not specifically about belt-fed AR's, which I know nothing about.
There are different types of belts.
Disintegrating belts are used in all modern U.S. weapons I'm aware of. They break into pieces after the rounds come out, and are typical of our throw-away society. Cheapskate Eastern Block nations tended to favor
non-disintegrating belts, which inconvenently drag on the ground on the "fired" side but are more likely to be re-used in the field.
Perhaps a more important division (as far as gun design is concerned) is between
pull-out belts and
push-through belts. Browning .50 and M1919 .30 types, and probably all the old designs for cloth belts, use the pull-out style. The Browning .50 has a pivoting arm on the bolt that snaps over the rim of the round in the belt, then pulls it out and slides it downward into line with the chamber as the bolt moves back. Most more modern designs, like the M60, M85 and M249, use push-through links. Such links are split on the side that faces toward the bolt, so a lug can pass through and simply ram the round forward into the chamber.
The Mk. 19 grenade machine gun fires it's rounds without removing them from the links at all, though the links do disconnect from each other in the process, which resembles a pull-out arrangement. This is possible because about a half inch of the cartridge case is still sticking out of the chamber when the round fires.
As far as belt feeding goes, typically there is a "belt feed pawl" that is cammed back and forth by the movement of the bolt. This pushes the rounds forward (sideways) one at a time. While the belt feed pawl is doing its return stroke, the belt is prevented from going back with it by a "belt holding pawl" which pivots from a fixed point. On the Browning .50, the feed pawl is in a cross-slide in the top cover and is operated by a lever that engages diagonal tracks in the top of the bolt. The holding pawl pops up from the underside of the feedway.
The M60 and several other designs attempt to smooth out the belt feeding process by doing half on the back-stroke of the bolt and half on the forward stroke. They have two sets of feed pawls with alternating action, and a holding pawl is not needed.
Some machineguns use a rotary wheel, actuated by some type of ratchet linked to the bolt, to feed the belt. The only one I can think of is a Soviet design.