Howdy
Here is another very early type of metallic cartridge. You may or may not have seen this photo on another thread. These are Benet primed, copper cased, folded rim cases. These are centerfire, but they are not Boxer primed nor Berdan primed, they are Benet primed. The round all the way on the right is a modern round, with a modern solid head case, all the others are Benet primed.
Benet priming was developed by Stephen Vincent Benet, grandfather of the famous poet with the same name. Benet went on to become Chief of the Ordinance Department, but the priming that bears his name was developed earlier when he worked at the Frankford Arsenal near Philadelphia.
Here is a photo showing some Benet primed rounds cross sectioned. The folded rim construction of the case is obvious. From the rear, these rounds look like rimfires, because there is no separate primer, but they are not. Priming compound was deposited onto the flat inside face of the base of the case. Then a copper Anvil Plate was inserted and pressed down against the priming compound. The Anvil Plate was held in place by two crimps on the side of the case. When struck by the firing pin, the priming compound was crushed between the soft copper case and the Anvil Plate. The flame from the priming compound flashed through the two holes in the Anvil Plate to ignite the main powder charge. One can always tell a Benet primed round because of the lack of an external primer, and the two crimps on the side of the case.
The Benet primed rounds needed to be copper cased so the material was soft enough to be deformed by the firing pin. Notice the tiny rim on these rounds. This was the very first version of the 45 Colt round. As a round for the Colt, a large rim was not necessary for extraction because the ejector rod of the Colt popped the empties out from the inside. All the rim had to do was hold the round from being shoved forward in the chamber when struck by the firing pin.
The rounds in the top photo are the 30 grain Army loads, but commercial rounds like this carried the full 40 grains of powder that we often read about. Incidentally, folded rim rounds like this had more case capacity than any other style of case, including Balloon Heads. When Balloon head rounds came along, it was more the norm that they would have about 38 grains of powder in them instead of 40. But gunwriters like to talk about 40 grains in the 45 Colt.
The soft copper was eventually the down fall of Benet primed rounds. Early 45-70 Government rounds had the same construction, somewhere I have a photo of one. But with the 45-70 Benet primed rounds the Trap Door extractor would sometimes rip through the rim, leaving the rifle jammed with a torn case in the chamber. Not a good thing in a fight.
Eventually the Army went to other forms of priming.
