I know this is a bit outside the bounds of normal gunsmithing, but I've had to folks lined up for this project that have fallen through, so I thought I would reach out here and see if anyone knows a shop that might be able help.
I have a replica 3 pounder Whitworth cannon (2" bore). It's a breechloading gun, but unlike the original, it's a smooth bore, not rifled. Now, the problem is that if I use the normal muzzle loading cannon technique of a seperate powder bag and ball, you still have to ram it from the breech to make sure the ball hasn't rolled away from charge (with a true rifled gun, the project engages the rifling first and gets held in place until fire, preventing that issue. Plus, the powder "bag" (it's tin foil) typically needs to be punctured before firing, as the 209 shotgun primer doesn't always punch through. So, the way we did it before is to have someone push the ramrod down the muzzle, holding the ball against the charge and the charge against the breech block, then remove the firing mechnism, puncture the bag, and then screw the mechanism back in (get the rammer out of the way), load the 209 primer, and then fire. It's cumbersome and really defeats the purpose of having a breechloading cannon to begin with.
So, what I want to do is have some cartridge cases made up out of steel (with a simple hole instead of a convention primer pocket, since the gun is exterior primed, which is both historically accurate and prevents it from being a Destructive Device as classified by the ATF). I can have the powder charge bag inside the cartridge case, with the projectile put on top of it (maybe held in with some tape, just to keep it as a unit, if press fitting doesn't do it). That should let me increase the firing rate, plus make it way easier to puncture the bag with the breech open, then simply close the breech, simplifying the loading procedure.
The cases would be about 6" long and probably just a hair less than 2" in OD, since the barrel is exactly 2" ID, with a relatively thin rim on the outside, as it's just meant to hold the case in place while the bag is punctured before the breech is closed (there is a small amount of clearance for a rim between the breech block and the breech face, I'll have to hunt down the measurements).
Anyway, the shop I started with on this doesn't have the bandwidth to work on this and the hobby machinist friend I have who was going to give this a try has his lathe down, so he can't do it.
I'm also wanting to talk to someone about building a lead mold for a projectile for the gun that would work with the gun and let me cast them at home (unfortunately, the 2" diameter is just a bit too small to use the normal expedient of concrete filled soup cans, as I can't find a roughly 1.95" diameter standard for cans to use). I made a rough sketch up of the projectile I'm thinking about (hollow base to try to provide stability and ease up the weight that a solid lead project would have, since the original guns fired iron projectiles.
And just for fun, here is the gun the first time I had it out at the range (last Fall's Proteq INGO shoot):
[video=youtube;6J6LSPeIKjU]https://www.youtube.com/watch?v=6J6LSPeIKjU[/video]
I have a replica 3 pounder Whitworth cannon (2" bore). It's a breechloading gun, but unlike the original, it's a smooth bore, not rifled. Now, the problem is that if I use the normal muzzle loading cannon technique of a seperate powder bag and ball, you still have to ram it from the breech to make sure the ball hasn't rolled away from charge (with a true rifled gun, the project engages the rifling first and gets held in place until fire, preventing that issue. Plus, the powder "bag" (it's tin foil) typically needs to be punctured before firing, as the 209 shotgun primer doesn't always punch through. So, the way we did it before is to have someone push the ramrod down the muzzle, holding the ball against the charge and the charge against the breech block, then remove the firing mechnism, puncture the bag, and then screw the mechanism back in (get the rammer out of the way), load the 209 primer, and then fire. It's cumbersome and really defeats the purpose of having a breechloading cannon to begin with.
So, what I want to do is have some cartridge cases made up out of steel (with a simple hole instead of a convention primer pocket, since the gun is exterior primed, which is both historically accurate and prevents it from being a Destructive Device as classified by the ATF). I can have the powder charge bag inside the cartridge case, with the projectile put on top of it (maybe held in with some tape, just to keep it as a unit, if press fitting doesn't do it). That should let me increase the firing rate, plus make it way easier to puncture the bag with the breech open, then simply close the breech, simplifying the loading procedure.
The cases would be about 6" long and probably just a hair less than 2" in OD, since the barrel is exactly 2" ID, with a relatively thin rim on the outside, as it's just meant to hold the case in place while the bag is punctured before the breech is closed (there is a small amount of clearance for a rim between the breech block and the breech face, I'll have to hunt down the measurements).
Anyway, the shop I started with on this doesn't have the bandwidth to work on this and the hobby machinist friend I have who was going to give this a try has his lathe down, so he can't do it.
I'm also wanting to talk to someone about building a lead mold for a projectile for the gun that would work with the gun and let me cast them at home (unfortunately, the 2" diameter is just a bit too small to use the normal expedient of concrete filled soup cans, as I can't find a roughly 1.95" diameter standard for cans to use). I made a rough sketch up of the projectile I'm thinking about (hollow base to try to provide stability and ease up the weight that a solid lead project would have, since the original guns fired iron projectiles.
And just for fun, here is the gun the first time I had it out at the range (last Fall's Proteq INGO shoot):
[video=youtube;6J6LSPeIKjU]https://www.youtube.com/watch?v=6J6LSPeIKjU[/video]
