An edge shooter is a gun which fires gliders or other spaceships beyond the edge of the pattern, so that it can be used to fire them closely parallel to others. Compare glider pusher, which can in fact be used for making edge shooters. The Fx119 inserter is another more extreme example, with a whopping 25hd clearance.
Herschel circuitry includes several components that can be used to build edge-shooting guns with adjustable period, depending on the input signal.
Edge-shooting guns are useful in the creation of shotguns that fire salvos of gliders or spaceships. Often such shotguns are components of more complex guns that repeatedly produce spaceships via a known glider synthesis.
The term "edge shooter" is also used for any repeatable reaction -- not necessarily a fixed-period gun -- that inserts a glider or spaceship onto an output lane without needing support by any persistent structures beyond that lane. Many recent large spaceship and rake mechanisms, such as the half-baked knightship, centipede, weekender distaff, and engineless Caterpillar, include edge-shooting seeds constructed and triggered by slow salvos.
Paul Callahan found a p46 edge-shooter in June 1994: