Magazine cutoffs were a staple of some 19th/20th Century military rifles. They were to be used in single shot mode, with the magazine in reserve, till some wise officer ordered them released, and then to be used as repeaters.
This modification apparently is not for rifles alone, as Webley automatic pistols have this feature as well, no doubt mandated by some government agency. The system works with the magazine, which has an extra locking hole, where the magazine is not inserted all the way and locked in the second hole, keeping the bullets held in reserve and out of battery. The slide doesn't use the magazine to lock open after firing, and the shooter has but to drop another round in that big .455 hole and continue shooting. If repeating operation is desired, the catch is pushed and the magazine shoved home.
The feature does seem odd in a pistol, but it is simple and it works. The commercial pistols seem to have this cutoff also. The original idea of a magazine cutoff was an officer controlling the behavior of his troop of men. In the British Army, there were few men who weren't officers and carried pistols. Very confusing. At the time cutoffs were in vogue, the idea had some merit, as the British Army was usually a long way from home, really outnumbered, and every cartridge had to be carted the whole way on someone's back.
My friend Roy Shadbolt kindly sent these pictures of his .455 Webley pistol showing the magazine cutoff details.
One of the main features of late 19th Century and early 20th Century military rifles was the magazine cutoff. Repeating rifles have been plaguing logistic types since the American Civil War with the thought of expending huge amounts of ammunition. Someone has to pay for that (you would think the Generals is charge of logistics were paying) and someone has to keep everyone supplied. All that aside, the first use of the magazine cutoff in battle actually saved the hides of the men carrying Spencer carbines.
I wrote about Ranald Mackenzie in an earlier post, and one of his responsibilities running the 4th US Cavalry was keeping the Commanches at bay. Commanches were not push overs in any stretch of the imagination, and his command got tangled up in a large group of them in the Battle of Blanco Canyon.
The Indians were in no mood to settle in a reservation, and Mackenzie and the 4th Cavalry aimed to put them there. In pursuit, the column entered Blanco Canyon and were promptly set upon by hundreds of Commanches. One Lt. Carter fought a rear guard action while the main column sought to escape the trap. Carter had his men close the magazine cutoff in their Spencer carbines, and had them use single shots till they were to make their break as the last of the column. At the last moment he told his men to release the cutoff and pour it in to them. The Indians were shattered by the volume of fire the troopers dished out. They made their escape and the troopers only lost one man during the entire fight.
Magazine cutoff just before trigger. This rifle sold at auction.
Lt. Carter was awarded the Medal of Honor for that action. His quick thinking saved the day, but an action like that would not be repeated, as the cavalry was soon to give up their Spencers for Trapdoor Springfields. As Custer was to find out, those carbines had no magazine cutoffs, as there were no magazines. Repeating rifles would return to the cavalry, but not until the turn of the century.
Medal of Honor Citation
Second Lieutenant Carter, Robert G.