Howdy!
I am in the US but like to learn all I can about the 44-40 from other countries. I have never herd of "fac" before so I have no idea what or who that is. I assume it has to do with ordering firearms. Although other "44's" may not be available there, I have no idea...there are other names that are different cartridges and even different names of firearms. It can certainly get confusing!
Cartridge companies don't always call the cartridge the same name as the firearm manufactures name....adds to the confusion.
Firearm Manufactures
When Winchester first manufactured the 73' (as we know it) it was called "The New Model of 1873", not 44WCF, 44-40 or even 44 Winchester. To back up a little in history, the 44 Henry and the 66 Winchester are both referred to by Winchester as the "Henry Rifle of 1860" and the Winchester "Model of 1866" in Winchester's 1873 catalog. The "44" caliber is never mentioned as the firearms name.
So the "Official" factory names were:
1. Henry Rifle of 1860
2. Winchester "Model of 1866"
3. Winchester "New Model of 1873"
Eventually nicknames were given such as "44 Henry", "44 Winchester" to both the 66' and 73'. What got confusing was the ammunition designations. One would need several different variants of 44 Henry ammunition for the 60' and 66'
Too step up the confusion, Ammunition manufactured didn't help much. By 1870, this is what one 44 Henry ammo box looked like!
Just plain ole 44/100 for the Winchester repeating rifle. Since the Henry of 1860 technically was not a Winchester, the confusion was toned down a little with this one.
When the Winchester New Model of 1873 was available, the ammo was still called the 44/100....however inside the cartridge picture, it said "Model Winchester 1873" as well as mentioning the new "Center Fire Cartridges" call-out as can be seen in this photo,
It wasn't until about 1877 that the ammo box was changed to replace the 44/100 to ".44 Cal.", but referred to as "Winchester Rifle Model 1873"
It was not until 1884 that the cartridge case heads were stamped "44 W.C.F.". By this time the rifle and cartridges had nicknames that we have all herd of at one time or another. 44 Winchester, Winchester 73, etc.
Union Metallic Cartridge Company (UMC) was a very popular cartridge company. Their case heads were stamped "44 C.F.W.". UMC worked closely with Marlin too and by 1886, it was Marlin that got UMC to use the designation 44-40. In the mean time, Winchester rifles could be marked 44CF while Marlin rifles were marked 44W.
To keep things confused, then there was the literature that really kept things going. They were called 44 Winchester's, 44 Marlin's and even 44 Colts even though there was a real "44 Colt" of earlier make that was actually a .45"
On the back of a 1930's Bullseye pistol powder can shows load data, calling the 44-40....... "44/40 W. & M. For Revolvers". On the back of a 1930's can of Unique pistol powder shows data calling the 44-40......."44/40 W.C.F."
The list goes on but for all practical modern purposes;
Firearm
44 Winchester = 44-40
44 Marlin = 44-40
44 Colt = 44-40