I'm looking for suggestions on my quasi-swivel gun/mini-cannon project. My main sticking point is the various rules and regulations from reenactor societies versus what I believe is a great utility in properly cleaning the cannon regularly, as I do with other muzzleloading arms.

On one hand, yes, welded breech plugs are required by both N-SSA and AAA, but neither holds my interest. I'm building purely for my own enjoyment. On the other hand, being able to remove the breech plug for end-to-end cleaning and rustproofing, as I do with my other muzzleloaders, seems harmless as long as the threaded portion is sufficiently strong to hold the pressure, along with being machined in such a way as to properly tension the plug. I don't see any obvious safety concerns, and I suspect that both the N-SSA and AAA have their rules in place to make things quick and easily verified as safe for the crowds.

I'm making the barrel itself from A519 1026, with plenty of wall thickness, and the breech from 1045 HR, with the eventual goal of making something along the lines of the following:



Any experience you have to share would be most welcome.

There a 3 to 1 rule at the breech , meaning you want a one inch bore your OD at the breech must be three inches .
Most small cannons do not have a removable breech plug .

If you really want to lean about cannons and shooting them safely go to Grey Beard Outdoors and look at the Black Powder Cannon Forum .

Nothing else comes close .

Small Bronze VOC Gun

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French 75 by Dominic Carpenter

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Confederate Parrott gun , Golf Ball bore .

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Welds and threading are not appropriate options. Interface fit and pinned breach plug or prepare to have people who know about these things tell you you're doing it wrong...because you are.

You will have to look up the type of interference fit you will need, but you will have to hear the bore and freeze the plug, you want to keep the edge of the plug going into the bore nice and sharp, so chamfer the edge of the bore to make it easier to drive in. You're going to need a forge and liquid nitrogen...and a lathe.

Might want to tell N-SSA and AAA, along with every "mentor"-level member on the GBO forums that. Welding is, apparently, the only acceptable method of fixing a breech for reenactors.

I could certainly do the welding to their spec, or your (I'm assuming) 0.020"+ interface fit and pin, but I don't see the issue with threading the breech in as on a rifle, but on a larger scale with substantially more thread interface. What, specifically, is the concern or objection you have?

Where but at the GBO forums do you think I learned of N-SSA and AAA requirements? I'm not a reenactor, nor do I have interest in it.

The OD isn't an issue, I have that (and the chamber dimensions, since I won't be doing a bore-diameter chamber) well in hand, but I genuinely appreciate the concern.

Is there a reason, past tradition and traditional methods of manufacture, for shying away from having a removable breech?

I'm just sharing what I was told when I built a 1.14" bore BP cannon. I was told sternly by people that build them that welding was not acceptable because even with a friction fit plug, gasses under firing can still get between the plug and bore, BP bores must be cleaned or they corrode (obviously). You can't clean between the plug and bore if any gasses get there, so it will eventually corrode and get worse, and weaken the breach. I was told doing such things has killed people, oh not the first firing, or the 30th, but 5- 8 years later when it's sat for a while and someone decides to break it out for 4th of July and fire a max charge.

I'm no expert, just repeating what I was told.

I'm positive a muzzle loaded BP cannon is a non-legal issue. A breach loader..... not nearly as sure as I think there may be legal restriction, I'd definitely research it before building one.

That reasoning is exactly why I want to treat it the same way as any other muzzleloader, frankly.

Antique ignition system, no fixed cartridge, and it's still a non-firearm for GCA/NFA purposes. I'm not making a breech loader, but a threaded breechplug on a muzzleloading cannon.

After far too long of a delay I've finally received the last of the tooling I needed to replace.

Some time during April I'll be starting this project. I will be taking a few pictures as I go and once I get to the point I proof the barrel will report back.

Looking forward to the progress reports !

Welding a breach plug is good for the first shot. As mentioned above there is no way to tell if there are any corrosion issues between plug and barrel and when that will become a problem

For a threaded breach I agree with three times bore diameter. Plus a short unthreaded section that extends into the bore fitted to bore diameter. Threading type is also important. A course thread will have more resistance to recoil on the plug/barrel interface than fine threads will. And will give longer service after multiple plug removals and installations than fine threads will.

Buttress thread is best, if you are cutting the threads on a lathe.

I am going large for the 1026 tube/1045 plug cannon with plenty of thickness around the breech. The unthreaded "plug" forward of the threads was also part of the plan as were coarse threads. I figure copying what worked in the past - but with modern materials - will work just fine.



I gave it a thought and almost went that direction but I settled on traditional 60° V-threads for this just for ease of machining and due to my tooling. Plus - as stated above - it worked just fine in the past for later blackpowder era cannons of such small bore.

One of these days I'll buy some more HSS blanks and make or buy a new boring bar but for now I can't excuse it as business related as I can with the insert tooling.


Along with the 1026/1045 example I've also decided to see how relatively thin wall (0.25") normalized 4130 does as an oversized musket or punt gun of the same bore diameter. I'm curious what it will take to make it burst and I intend to proof it to failure prior to making one to keep.

FYI~

http://www.buckstix.com/HowitzerBarrel.htm

I'm now interested in this build from a mechanical standpoint.

What welding process and procedure is typical for a breech? Are most builders using a flat cap and fillet welding it? Dome cap with butt weld?

In my opinion (as a pipe welder), the only suitable way to weld a breech in would be by use of a domed cap (or similar), with a proper open-root butt weld using TIG. I'd be looking for a completely smooth deposit on the root pass. Would probably run a purge even on a material that doesn't require it, and considering the heft of the materials, a good preheat, which would be required on a steel such as 1045. You'd also want to look into appropriate post-weld heat treatment.

The major concern mentioned in this thread is the corrosion, and I concur it is going to be an issue long term using BP if there are any orifices for the fouling to enter. If a fillet weld is used, or the root reinforcement on a butt weld has any nooks, rippling, etc, it will provide a place to begin stress-corrosion-cracking. The root must be 100% melted down smooth.

Threads seems like the better option. They will allow full cleaning, thusly no corrosion. I would worry about gas blow-by, but my guess is a very long NPT style would work. Cut the threads 2 or 3x longer than normal, to ensure strength, and with typical thread sealant and the NPT end, it shouldn't leak.

The usual procedure I see recommended is to deep V-groove and circumferentially weld the plug in from the outside of the barrel/liner - along with plenty of length of plug press-fit into the barrel. Not specified on the rod or process used but I see people using anything from FCAW "MIG" to TIG to good old stick with whatever rods they have handy. It all seems sketchy until you realize that to meet the requirements photos of before/after and during the build and assembly are required to certify the barrel - along with proof testing. That obviously leaves the entire joint inside the barrel entirely open for corrosion which will inevitably occur. Cannon barrels are seen as disposable I suppose. The original cast barrels certainly were. They were fired so many times and then considered unsafe. When dealing with bronze I suppose it wasn't the end of the world to only fire it a few hundred times before sending it in to the armory to be melted down and cast anew.

You can see why I've settled on threading. I'm not planning to use tapered threads as it doesn't seem to be needed. If I have issues with leakage around the breech I plan to groove it and turn a brass or copper obturator.

This project has been temporarily delayed due to a minor disaster in my shop. A wind storm caused some damage to the building and that took all of my attention and free time lately.

I'm hoping to finish the machining this week and proof test the barrels next weekend.

Still seems a taper thread would be better, but any which way, I think a threaded joint is the superior method here verse welding or press/pin. I love welding because it's permanent, but that's the major detractor as well.

If done as a pressed plug with V groove, most any process could be used, but then I question weld strength considering the sheer amount of pressure, particularly as a very quick shock load opposed to gradually increasing pressure. I'd be cutting a VERY deep groove in there.

Do you have reference material or engineering consulting to back up your choice of thread size/pitch? I'm sure someone has calculated and tested these things ad nauseam, but what do YOU know?

What is the peak pressure looking like in a typical cannon? 20kpsi?

Maybe one day I'll build my own cannon. I definitely want to. At least a golf-ball, probably a tennis-ball size to pack with light loads as a dog toy.

Sure I have reasons behind my chosen thread OD and pitch. Machinery's Handbook. Even with modern materials I'm still overdoing the safety factor for the specific loads I'm planning on.

There is no typical cannon. Pressures can vary wildly and that's why so many people suggest sticking with the existing designs (or scale versions) and known-good loads. Off the top of my head here are a few things that will impact both peak PSI and dwell at higher pressures:

Rifled or smooth
Windage
Grain size
Projectile weight

I'm certain I could come up with more but it's nearing midnight where I am.

Any progress on the build?

Just found time to cut the tubing to length and face it last night. Hopefully after a bit more work today I can get back to it.

Cleaned up a few torch cut M61 muzzle half barrels too. Looks like I'll be making some .79cal rifles too.

The little swivel gun worked out great. Proof testing went well as expected. The breech seals beautifully and the 10° taper with matching taper inside the barrel worked similarly well to keep gas out of the threads.

I just have to band the trunnions on and pop it on either a yoke and pole or a sled. I haven't decided and might actually do both.

I forgot to actually stop and take many pictures but hopefully these two get the idea across.

Neat.

I thought so. I blued it as well but only have a picture just after bluing.



Don't see anywhere near enough blued cannons. Usually it's paint.

Looks great.

What's your proof load going to be? Regular max?

Indeed. I measured various points breech to muzzle and after what I consider the maximum charge was used I measured it again. No change so I sent a few more. No change in measurement. Perfectly safe with that charge.

Of course - my main use is going to be salutes. On the occasions I do fire it live I will likely use lighter weight projectiles than the cast zinc balls with which I proofed it.

Cleaning went as well as expected. Clamped down thoroughly and of course with a large wrench the breech plug came out. Reinstalling it was a breeze after cleaning and I just torqued it until the index lines matched again.

Overall I'm pleased with this project.

The next barrel will be far more interesting to me - a relatively thin walled 4130 cannon. It will be very interesting to see what it takes to burst such a barrel.

Glad to hear she's good to go!

Why zinc?

Able to get those threads cleaned out easy? Antiseize? Did I miss wrench flats in the pictures? I assume you're not putting a pipe wrench on that beauty. Strap wrench has enough ass? Guess it depends on your torque spec. I'm guessing around 100ftlbs?

Zinc is about as light as iron and a lot easier to cast. It's nowhere near as heavy as lead. 11.5oz versus 17.5oz. The polymer projectiles I'll likely use when I don't use zinc weigh about 2oz - but I do plan on having this be mostly for celebrations. It's mostly going to see salute charges and little else.

The threads - both on the plug and inside the breech - scrubbed right out with a copper brush. Easy! Cleaning the bore was a snap with some hot soapy water as well.

I thought about using antiseize and almost didn't. I ended up going with a few small dabs of Permatex copper. I'm glad I did as it didn't seem to harm anything and certainly didn't hurt.

No flats - I didn't like how they would look. Rosin and hardwood blocks! No joke. One set in the barrel vise and one set on what amounts to a giant torque wrench as the jaws.

Assuming no slippage occurred I applied 450ftlbs of torque. It seems like a lot but it amounts to a gigantic fastener. Similar fasteners are spec'd for 4000+ ftlbs.

I painted a couple of projects long ago, was never really happy with the results. Been bluing ever since.

Like this recent 1" bore 1841 6-pounder. Machined from 1018 round. Solid breech, bored from one piece.




Pre-blue . . .




Or this golfball Coehorn . . .







Coehorns are addictive, but I can stop anytime. I can, really . . .

I knew there had to be others bluing their mini-artillery!

Looking great. I may have to go with oak instead of mahogany for the carriage for mine.