12mm pinfire
A decent number of pinfire revolvers came into the US and Confederate States during the Civil War. Both sides were quite willing to buy about anything which could shoot. Either to issue to troops, or to keep the other guys from getting it.
I've never seen much, really anything, concrete on pinfire revolver ballistics. I've read somewhere they weren't well liked in North America, because, in effect, they didn't "shoot hard". This compared to percussion revolvers, despite the much greater ease of reloading. I don't think I'm going out on much of a limb to say in 1861-65, percussion revolvers were the gold standard.
The Union used Colt, Remington, Whitney and Starr revolvers, primarily. The Confederates mostly used native copies of Colts, and never really had enough.
Pinfire cartridges were loaded in the US. Again, I have no hard facts, but apparently not for very long.
Anyway:
Got to look at 1 unfired round of 12mm pinfire. Copper case, lead bullet quite whiskery from oxidation.
Headstamp was maybe "C S" in italics, best I could read it. The striking thing was that it had a hole punched in the case side about 180 degrees opposite the firing pin, just forward of the case head. In that was inserted a percussion cap. It was neatly done, I think factory work.
(1) The ignition system used the chamber wall as the primer anvil.
(2) Imagine how low the pressure had to be for that to work.
Pinfires are strange.
12mm pinfire
by Slow Hand 
, Indiana, Monday, March 11, 2024, 08:18 (47 days ago) @ A K Church
Agreed that pin fires are odd.
I have read some modern accounts of reloading pin fired rounds. Basically is using a suitable centerfire case with either the primer pocket licked with a brass plug, solder or just a fired primer and ahold drilled for a simple brass rod for a firing pin. Drop a percussion cap into the case and line it up with the pin, push the pin in to hold it in place and go from there.
I’ve also read of a guy who added a center fire pin to the hammer of a bonfire gun and drilled out the recoil shield to allow use if standard, properly formed, centerfire cases. This was for reenactment use with blanks only. Not sure how well hit wood work with live fire but can’t see it being too horrible.
You mention low pressure, that makes me wonder what kind of pressures various black powder loads produce. I’ve always figured you cans stuff enough BP in a case to cause an issue (EK kind of priced that false), but it makes me wonder about such things as BP pressure of say a .45/70 vs a .45/90 or my little .50/45 vs a full length .50/70. It would be interesting if someone got their fancy piezo electronic deals really dirty and measure BP pressures of various loads and also of various powders including the substitutes. Hmmm. Off to google I go!
Sherman Bell did that with various BP cartridges
and wrote up the results in the Double Gun Journal. Lots of interesting info; one item was the effect different types of filler had on pressure in both NFB loads and BP loads.
Sherman Bell did that with various BP cartridges
by Slow Hand , Indiana, Tuesday, March 12, 2024, 10:16 (46 days ago) @ JohnKDM
John, have you watched this video, or this guy at all?
https://youtu.be/ONup8G2vpgE?si=jY3sZfw7oe3xNgFR
He is pretty interesting and has a thing for trying out different things. I don’t want to say ‘busting myths’ but he has no trouble going against the grain on ‘common knowledge’ to see what could happen with different setups.
Recently he was trying to get original .303 BP velocities. He’s done a couple other videos with various duplex loads and in this one does some odd stuff and comes up with some interesting information.
Have not seen him. I do shoot a lot of duplex loads
using SR4759 under Swiss 1.5 & 2f. Primarily for double rifle regulation as our BP is not equivalent to the original Curtis & Harvey #6. It does burn a lot cleaner with the smokeless kicker and since 1gr of smokeless is roughly equivalent to 3grs of BP, when you run out of case volume you can offset by adding the smokeless up to a certain point. S. Bell and G. Wright discovered when pressure testing you can overdo the kicker and exceed the original pressures. Most pressure tested safe loads keep the smokeless less than 10% of the BP charge. Aside - fillers, usually the dense ones, can raise pressures.
When he put the smokeless on top and gained velocity you notice he had flattened primers. Of course primer visuals are not always a good indicator, but what I think happened there was the smokeless lit after the BP pressure peak and caused a secondary wave peak. There was a French scientist (Paul Vieille) that worked with the effects of a pressure wave bouncing back and forth in a closed cylinder - and if it got in sync with another wave, the peaks combined and increased pressure as they bounced back in forth in a closed cylinder and slammed into the ends. His work using these ideas led to nitroglycerine being developed into smokeless powder (controlled burn instead of an explosion). This concept is a good theory behind barrel ringing at the base of a bullet if an air gap is left in a BP case.
Even though the bullet is moving, it might apply here as well.
Have not seen him. I do shoot a lot of duplex loads
by Slow Hand , Indiana, Tuesday, March 12, 2024, 18:24 (46 days ago) @ JohnKDM
I remember you running out of velocity in your doubt rifle and thought you had worked with duplex loads to up the speed for regulation.
It wo7ld. Interesting to see what the pressures were doing with his backwards and mixed up duplex loads!