12 mm pinfire cartridge with oval bullet

Does anyone have ever seen an example of a 12 mm pinfire cartridge loaded with an oval bullet? There is a Lefaucheux revolver with oval bore made for this cartridge but I have never seen pictures or information about this odd design.

New to me and as you know the Lancaster Oval bore was not a true oval-bore as such, but just used wide smooth shallow grooves to provide rotation.

Could this be just piggy-backing the design? How do the time lines match?

Pete, thanks for the help, but this cartridge was made for a true oval bore. Cylinder chambers are cylindrical but the front section match the oval shape of the bore, so a normal cartridge won’t fit.




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Amazing, truly amazing.

The designer / inventor must have had some method of indexing the pin to the bullet, to the round cylinder chamber, to the oval bore, or this would have been a backwards lead-storm.

Plus I’d think a lot of energy would be lost in the bullet jump from the cylinder to the barrel, unless the cylinder / chamber mouth was also oval shaped.

Sure seems like a heck of a lot of work, machining & expense to make a new wheel. An oval bore of the shape shown, can’t be easy to make, said with my very limited knowledge of machining metal (I know how to run a file).

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I’d go not for oval as such but for “dsic shaped” or the shape of a flattened ball.

By way of understanding I assume that the oval shape of the bore of the barrel is parallel and does not have any helix (i.e. is not rifled so to speak). I am trying to get my head round how this was produced, as Pete said “amazing”. As to cartridge to projectile orientation, based on the assumption that the cartridge case circular dimension being the half the sum of the maximum and minimum, plus case wall thickness. It would not be too difficult to coin the case in a split die thus setting the position of the pin. I am totally intrigued to know if the projectile was a round discus shape or had parallel rear portion, if not how was a gas seal achieved, absolutely fascinating.
Thanks for posting.

Mike, yes, the bore is parallel but each side has three straight rifled grooves. The firing pin of the cartridge case was used to index the bullet with the barrel. A very intriguing design, indeed.





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Hi Fede,
Yes it would really have to be or the transition from chamber to barrel would be horrific to say the least. Thanks for these pictures, it does make it easier to visualise. As to the three groves being of any use I really have my doubts, really intriguing concept, glad you posted it.

Just need your wish now, for a picture or drawing of a complete bullet.

@Fede are there more pics of the gun?

The slots for the pins look extra wide. I wonder if it took an adapter cartridge only and not a regular cartridge, similar to this one I had:

I asked Guillaume Van Mastrigt about it.


Are those “standard” nipples on the cartridges, like a #10/11 cap?
That is very cool!

Yes a standard size cap, but not the ones used on standard percussion pistols.

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Cool, thanks!!

Apparently I have the book where these came from. I probably should read through it again!


Aaron, those you posted are the same found in the “The Pinfire System” p. 196, but my pictures came from an article published in Gun Report April 1968. Information is basically the same.



we think this gun uses common bullet ctges.
What is important is the fact the front of the bullet must be small enough in diameter to enter the rear part of the ogival portion of the chamber.
Cartridges with pointed bullet are ok for that.

Without dimensions of the chamber it is hard to be sure.


A cartridge with a regular bullet won’t fit the chamber because the change from cylindrical to oval is abrupt.

hi Fede

  1. exactly the same for a conical bullet as for an oval bullet if the case of the case is standard length

  2. and if it is a short case ctge (i the book the guy doesn t give dimensions of the chamber therefore we do not know the length of the cylindrical portion of the chamber corresponding to the case of the ctge) even a round nose bullet ctge is ok

  3. an oval bullet is crazy because you have to index the pin very accurately for each cartridge you make !!

it is what we think in france (not specialy me but people expert in old guns)