 Greener Choke bores also won at the London Gun Trials of 1877 and 1879, and the Chicago Field Gun Trial of 1879.The results of these trials were responsible for making the W.W. Greener name famous, and for confirming the practical advantage of a repeatable method of controlling the performance of a choke on a shotgun.The exit end of a choke is smaller by some dimension than the actual bore of the barrel.