Period-59 glider gun is the first true period 59 gun, discovered by Adam P. Goucher on December 3, 2009. Jason Summers helped by providing a period-59 five glider to six glider reaction and also a 180 degree reflector reaction.

The core of the gun is the 5-to-6 reaction (an over-unity reaction), composed of two copies of a mechanism hassling two pi-heptominoes, in a fashion reminescent of the p44 pi-heptomino hassler. Of the 11 glider streams linked to this:

Two link together via a 180° reflection off a p59 oscillator. Four are pairwise linked to a single copy of the basic mechanism. This functions as a two-to-two glider reflection reaction on its own, rerouting two parallel glider streams (one incoming, one outgoing) into two sideways ones. Four of the core streams are redirected using 90° reflections off further p59 oscillators (and some tertiary pairs of reactors) and to link with the four streams from the secondary reactors. This leaves one output stream. The discovery of the Snark in 2013 enabled Dave Greene to build a much smaller variant with a bounding box of 405×355. Entity Valkyrie reduced this to 327×227 in October 2018— a slightly optimized 293×218 version of that gun is displayed below.