Eley Bros Factory Drawings for Pinfire Cartridges
Here is a selection of factory drawings/blueprints for how Eley Bros made pinfire cartridges. These blueprints date to the early 1900s.
First up is the 5mm pinfire cartridge drawing. There is a lot going on here! It lists the dimensions for the bullet, the pin, the percussion cap and the case. They also give all of the dimensions in imperial units though these cartridges were always sold by their metric designation, “5mm.”
The bullet is described of being made of 98% lead and 2% antimony. The antimony was an additive used to harden the alloy. It was a hollow bullet with an overall diameter of .207 inches, or 5.258 millimeters. It had an overall height of .300 inches or 7.62 millimeters. The bullet weight is 18 grains and the powder charge is listed as “about 1.5 grains.”
This matches up closely with examples in my collection which have a bullet weight of 18.0 grains and a powder charge of 2 grains. The overall weight is 35.2 grains.
The brass case is listed to have a mixture of 70% copper and 30% zinc to make up the alloy they used. The case had an overall length of .450 inches or 11.43 millimeters. They give the exact specifications of where to put the hole for the brass pin and even what angle the pin should be placed in the cartridge to ensure the hammers get the best hit.
Another unique feature about these smaller size Eley cartridges was that they had a small soft lead lump at the bottom of the case that held the cap and pin in place and provided extra protection to the bottom of the case to keep the explosion from the cap from blowing out the bottom of the case. This idea was designed and patented in the United States 60 years earlier by Christian Sharps when he sought to make the cases stronger for his pinfire cartridge design used in the American Civil War.
This 5mm drawing is also the only one that lists to metal composition.
In 1920 and 1921, a few years after WW1 and the merger of Eley, Kynoch, Nobel and others, copies of these Eley pinfire drawing (and many other cartridges) were transferred over over to Kynoch’s ammunition factory in Birmingham. Ronald Fenby, the head of the proof/inspection department kept copies of them in a notebook that were eventually discarded and made their way to collector’s hands many decades later.
This letter describes their 10-step process for the 5mm, 7mm, 9mm and 15mm cartridges. The process for the 12mm cartridges were described in a separate letter shown later in the article. For the 5mm, 7mm, 9mm the process was to:
- Cut and cup
- Anneal and clean
- Anneal and clean
- Draw and cut off
- Clean bright
- Assemble lead lump
- Form lead lump
- Print and mark for pin hole
- Drill hole, or bodge
The 7mm pinfire cartridge is made pretty much the same way as the 5mm. This blueprint does not list the metal composition though I would assume it is the same. The bullet diameter is .292 inches or 7.417 millimeters with a weight of 63 grains. The powder charge is about 5.5 grains.
A couple examples from my collection are pretty close but do not conform exactly. I have two pulled bullets weighting 62.3 and 65.1 grains, both came from cartridges with 4 grains of powder. A 7mm shot load example had 3 grains of powder and 31 grains of #8 shot. The overall weight of the ball cartridge is 102.2 grains which is just a hair heavier than the specification.
The 9mm pinfire cartridge blueprint has all of the same information as the previous and adds a few interesting new pieces of information. They indicate that the measurements represent the maximum sizes that the cartridge can be. They also list the composition of what is called their “pin-fire mix” in the next few drawings for the denotation powder in the percussion cap. It is made up of:
- 35% – Fulminate
- 15% – Sulphide
- 10% – Ground Glass
- 40% – Chlorate
The bullet has a diameter of .3645 inches, or 9.258 millimeters. And a weight of 124 grains.
The pulled bullet example in my collection has a weight of 123.5 grains and the cartridge has an overall weight of 181.0 grains, just 2.5 grains shy of the specification.
The 9mm drawing also mentions that the bullet shot from this configuration has a velocity of 520 feet per second measured at 20 yards.
The 12mm drawing gives a little different information. They still use a 70% copper and 30% zinc brass alloy and detail the size of the brass blank to start the process with. It has a diameter of 1.1 inches and a height of .014 inches. The process to make this 12mm case is:
- Cut and cup
- Draw and cut off
- Assemble lump
- Stamp and mark position of pin holes
- Assemble cap
- Fix pin
They also mention that the 12mm and 15mm use a paper lump rather than the lead lump used in the smaller sizes.
The 12mm bullet has a diameter of .440 inches, or 11.18 millimeters which is the only size that has a bullet diameter smaller than its marketing designation (12mm in this case.) It weighs 200 grains and actually has a slightly different composition with 3% antimony rather than 2%.
The example in my collection has a bullet weight of 204.9 grains and an overall weight of 280.4 grains.
The velocity observed at 20 yards for the 12mm pinfire is 600 feet per second.
The largest size is the 15mm pinfire cartridge. It has a .60 caliber bullet that measure .600 inches, or 15.24 millimeters. It weighs 450 grains and is again made with the 98% lead mixture instead of the 97% that the 12mm was made with. It was loaded with 28 grains of powder.
One thing that is unique to the 15mm is that they add 2 stabs (little indents) to the mouth of the case to help hold the heavy bullet in place.
The examples in my collection have a bullet that weighs 449.4 grains and was loaded with 28.3 grains of powder. The overall weight is 570.1 grains. So overall it is slightly heavier though the powder and bullet are pretty close.