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ARMAG

Search matches names, aliases and the text of every page. An arm found by its service designation is found by its alias, not its title.

Delayed blowback

Blowback with a mechanical disadvantage — rollers, a lever, friction or gas — slowing the bolt's opening without locking it.

Also called Retarded blowback

A halfway house between simple blowback and a locked breech. The bolt is never actually locked; something merely makes it hard to open quickly. Four ways of doing that appear on this site, and each is a different mechanism rather than a variation on one.

Roller-delayed, as in the MP5, drives rollers outwards into recesses through an inclined locking piece, so the light bolt head can only retreat by driving a heavier bolt body back several times faster. Lever-delayed, as in the FAMAS, does the same job with a pivoting lever geared against the receiver. Gas-delayed, as in the Heckler & Koch P7, taps propellant gas into a cylinder that pushes the slide forwards while recoil pushes it back. Friction-delayed — the Thompson’s Blish lock — relies on dissimilar metals resisting sliding under load, and is the only one of the four that does not really work.