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Discussion Starter #1


a rather crude CAD drawing i whipped up... anyone ever done a design like this? the only thing i can see there being trouble with in construction is cutting out the track for the bolt to lock into.

other than that, turn a solid piece of stock to slip fit the barrel, bore out the powder chamber, bore a hole for the piece that follows the track (i'm rusty on my gun terms...), making sure that it will result in the back of the bolt being flush with the back of the barrel, re-enforce the part of the track that the bolt would put the force against, and then attach a handle to the back.

what do you guys think?

purpose: easy cleaning, disassembly, reloading, emptying, exchanging of powder chambers, and so on. no welds to break


problems i can see would be the track in the barrel wearing out and getting all loose depending on re-enforcement and/or the quality of steel used. also might be a hassle to get to if you have a more vertically-firing gun.... this would be a good design for a little cannon that fires more flat, in which the breach can easily be accessed.

this might be a fairly common thing that is done in cannon designs and i just don't know it.. after all i am a noobie.
 

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Writing as an amateur, even if the locking lug or lugs held the pressure, which I doubt, you would have flame erosion, gas cutting and crud buildup so bad you could not open it.
It would be better to copy the 1861 Williams gun design if you are looking for a breechloading cannon.
 

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Very interesting idea but you have to be REAL careful with breechloaders. I see a few possible problems that come to mind with your design.

First, as jeepers1 said, the strength of the single pin that holds the breech into the barrel is critical. There'd be a LOT of force on it during firing and if it sheared you’d have a projectile flying out the rear. Three or four pins, evenly spaced around the tube “might” work OK but there’s no real guarantee.

The second problem is that there’s no seal between the barrel and the breach to keep hot gas from blowing back. That could be real nasty if somebody happened to be behind it when it went off.

The final question is could this design be classified as a destructive device? Remember that we’re limited to what we can do by the following law:

“Muzzleloading cannons not capable of firing fixed ammunition and manufactured in or before 1898 and replicas thereof are antiques and not subject to the provisions of either the GCA or the NFA. [26 U. S. C. 5845, 27 CFR 179.11]” (See the FAQ’s sticky)

While breech-loading cannons have been around for a few hundred years and there are a few types that are OK for our purposes, I don’t know if this design qualifies as a replica of an antique. Also, to the best of my my knowledge, there never has been a breech loading mortar. If that's the purpose of your design, it wouldn't qualify under the scope of the above stated law.

Since you REALLY don’t want to be building a Destructive Device, to be safe, I’d run a design like this by the BATF for a ruling before you ever build it.
 

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Step One: Write the ATF for approval of the design. Do not make any parts before receiving approval.
Step Two: Add more locking pins. Three or four total would be enough.
Step Three: Do not cut the locking recesses all the way through the tube. It should be cut maybe halfway through so the locking surface has some support. The way you have it now, the locking part will bend open from the pressure. Think about a bolt action rifle. There is a ring of metal surrounding the locking recesses. Your barrel material would need to be fairly thick (at least 1/2" in my opinion) and the locking pins should be at least 1/2" (and it would be better for them to be flat on the rear face to lessen the stress) for this to work.
 

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mortarnoobie said:
...
purpose: easy cleaning, disassembly, reloading, emptying, exchanging of powder chambers, and so on. no welds to break
....
GOOD START on the process. Powderchamber looks good - rounded bottom (rounded corners inside with flat bottom would be good too).

One large pin (size of the diameter of the powder chamber could be used as a cross-pin and trunion. Easy to disassemble for cleaning, big enough for strength. A step in the breach block (two outside diameters) could be used to deflect/limit blow-by. Outside form could be made to look like a Confederate mortar with ease.

I think I will be submitting a few drawings to BATF - just to make sure.
 

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Discussion Starter #6
i highly doubt i would be producing this design in reality.. it was just an idea i had, a spur of the moment thing. the points about hot gases escaping out the back are good, and are probably right on target. this design would require more refining before it could be used with peace of mind. all that aside, i fell asleep a few times drawing up what i already did, and since its just a concept,its not worth the trouble of making it more complete right now. maybe someday...

and ya, this would very likely be considered a dangerous and very illegal weapon to build.

by the way... what exactly is defined as "fixed ammo"?
 

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Fixed Ammo

Let me take a wag at that.
Projectile, propellent and ignition source in a rigid or semi-rigid self-contained unit.
Non fixed ammo is where the propellent, projectile and ignition source are loaded seperately.
 

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Discussion Starter #8
well thats good to hear.... i didnt think a pop can or tennis ball would count, but wanted to make sure. (unless of course i loaded the charge on it.

if someone were to do this (i doubt i would... it sounds like a hassle/sorta unpredictable), how would someone go about getting proof you did to prosecute you? (aside from finding unused rounds that you were carrying with you maybe)
 
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