Hello and welcome back to another edition of The Rimfire Report! This ongoing series is all about rimfire firearms, ammunition, and other related subjects. This week I’d like to start diving into some rather obscure or lesser-known ammunition types found within the annals of rimfire history. This week we’re beginning this ammunition history trip with a rather obscure but notable cartridge – the 17.5mm Danish Snider or more accurately 17.5mm x 29R (that is .69 caliber). This cartridge was used extensively with both the Danish Navy and Army leading to two different rifles being produced for it. The rifles began to see use sometime in the 1860s but there is much debate about which exact date/year the cartridge and rifle actually were pressed into service by the Danish military.

The Rimfire Report: 17.5mm Danish Snider – The World’s Largest Rimfire Cartridge

Snider Breech-loaders

The Danish Snider rifle was a major advance in firearms technology for the 1800s. As opposed to a muzzleloading percussion cap rifle, the Danish Snider made use of the Snider breech-loading system of American design. The action designed by Jacob Snider allowed a rifleman to fire and reload his single-shot rifle in less than a few seconds – a major improvement over its muzzleloading counterparts.

The Snider breech-loading design was so popular that many other rifles were converted from standard muzzleloaders to accommodate a snider-breech loading system. These conversions meant that many types of cartridges were used in the design and our point of interest today is the 17.5mm Danish Snider cartridge. From what little information I was able to glean, the Danes stuck with their 17.5mm cartridges while the British also upgraded their rifles with Snider breech-loading conversions but simultaneously made use of the much more powerful .577 centerfire Snider.

To get a good idea of how this action worked, I will reference YouTube user britishmuzzleloaders‘ video on the very similar MK II** Snider-Enfield Short Rifle. The action is very simply flipped open, a cartridge is loaded, the hammer is cocked, the action is closed and the gun is fired. Then the action is once again flipped open to extract the spent cartridge. Some of the pictures and videos presented here also give you a good idea of how simple the conversion was with even the hammer on the rifle being repurposed to hit a firing pin rather than a percussion cap.

Rimfire With a Twist

What’s really cool about the Danish Snider rimfire design is that there really didn’t even need to be a cartridge in the chamber in order for everything to work – just a primed rim. Since these rifles were all converted from muzzleloading firearms, the ramrods still existed on the converted rifles.

The breech of a Snider-Endfield

The Snider rifle could make use of its rimfire firing mechanism much like a percussion cap to fire off a full brass cartridge, a foil cartridge, paper cartridge, or no cartridges at all and just use the rimmed primer and load the rifle like a standard muzzleloader. I’m not sure if this was ever done in the field but it’s an interesting note to make that the design of the rifle meant you had a wide variety of ammunition options and weren’t limited to just fully loaded brass rimfire cartridges.

Round Composition Composition

There is very little information regarding the 17.5mm Danish Snider rimfire round and this is somewhat to be expected as the cartridge didn’t have a very large service life when compared to other calibers of the day. With this in mind, it is hard to tell exactly what the cartridge was composed of aside from what we know of firearms at the time. Obviously, a bare lead projectile would have been used along with the black powder.

Some reloading references online give bullet weights around the 385-grain mark and charges of about 60 grains of black powder. Given the case volume, this seems pretty reasonable but I don’t know enough about black powder loadings to know what type of results this would yield exactly. However, I would assume that it was more than enough to put down a decent-sized game animal or a human.

17mm Snider to the Left with 17.5mm Snider to the Right

As can be seen from some of the pictures here, the round itself featured a fairly heavy crimp around the ogive of the bullet – so much so that it seems like it would reach into the throat of the barrel. Modern reproductions of the round often dispense with refilling the large rim around the outside and instead, drilling out a smaller hole in order to insert a blank .22LR casing as a method for ignition.

Short-Lived and Oft Forgotten

The 17.5mm Danish Snider was quite an odd round even during the mid to late 1800s. While rimfire cartridges offered many advantages over muzzle-loaded black powder firearms, they paled in comparison to centerfire rifle and pistol cartridges which started showing up in the early 19th century and were in common use by the 1870s. The inherent disadvantages and obstacles of a higher caliber and higher power rimfire cartridges meant that rounds like the 17.5mm Danish Snider were all but obsolete just a few short decades after their introduction. Alas, the mighty .22LR lives on to today!

A modern reproduction of the 17.5mm Danish Snider made from aluminum.

Thanks again for stopping by to read The Rimfire Report! If you have any suggestions for obsolete or obscure rimfire cartridges or firearms, leave a comment below letting us know what you’ve come across. If you’re the proud owner of a 17.5mm Rimfire Danish Snider, let us know in the comments! We’d love to see your piece of history!