Hiram Maxim produced a second prototype machine gun in 1885. This is described in UK Patent No. 1307 dated 29 January 1885. This is an animation based on the patent drawings and shows how Maxim had simplified the mechanism. The second feed wheel of the first prototype was replaced by a pawl mechanism that moved the ammunition belt in front of the feed wheel. Maxim also improved the 'crankshaft breech' - when ready to fire the crank pin is on its forward dead-centre which locks the breech-block firmly against the rear of the barrel. When the gun is fired, the whole assembly recoils backwards until an arm connected to the crankshaft strikes a plate fixed to the non-recoiling frame. The crankshaft then rotates, and the breech is opened. For further animations of Victorian-era machine guns, search YouTube for vbbsm. Further details on these guns can be found in my web site - search for 'anti torpedo boat guns'.