breech-screw

The German and French marine methods permit the parts to be quickly exchanged when worn, but it is necessary to cut deeply into the walls of the gun, and to make the wedge, or breech-screw, considerably larger than the opening into the chamber.

Scientific American Supplement, No. 324, March 18, 1882 Various

Do not put oil into the vent, as it will clog the passage and cause the first cap to miss fire; but, with a slightly oiled rag on the wiper, rub the bore of the barrel and the face of the breech-screw, and immediately insert the tompion into the muzzle.

Ordnance Instructions for the United States Navy. 1866. Fourth edition. United States. Navy Dept. Bureau of Ordnance

The breech-screw should be taken out only by an armorer, and never in ordinary cleaning.

Ordnance Instructions for the United States Navy. 1866. Fourth edition. United States. Navy Dept. Bureau of Ordnance

Turn out the breech-screw by means of a "breech screw-wrench" suited to the tenon of the screw.

Ordnance Instructions for the United States Navy. 1866. Fourth edition. United States. Navy Dept. Bureau of Ordnance