Author Topic: Punt Gun? (Read 5853 times)

NitroSteel · « **on:** December 05, 2006, 09:35:14 AM »

Using this forum, I have safely made and fired (hundreds of times) a bowling ball mortar. It is amazing, everyone that sees it can't get over it. I've been using black powder, but ran out and used pyrodex successfully last week. I got within 30 feet of my target at 550 yards, I was proud...

One thing I would also like to make is a punt gun - - a gun like the market hunters used in the old days to obliverate ducks. Of course I don't want to obliverate any ducks, but I would like to mount it on something and shoot it just to watch the smoke and see it tear up some pumpkins or something...

Has anyone built one of these before? I know a shotgun barrel is long and thin and is safe. Would something like a 2 inch steel pipe be a way to start? Say 6 or 7 feet long with a thick steel powder chamber mounted/welded on the rear with a fuse hole, and secured in a "log" and then strapped down to a tripod of some sort? I do plan on using #6 or #8 lead shot just like used in a modern black powder shotgun.

I know this is a black powder forum and I would plan on using black powder in it and making it "legal" as a replica of something built back in the day. I have a book with pictures of several from the 1800's, but don't want to just build something that may not be safe.

Any ideas? Has this been done before? I couldn't get the search function to work.

Thank ya'll again,

NitroSteel

GGaskill · « **Reply #1 on:** December 05, 2006, 01:13:53 PM »

Sorry to be blunt but forget the pipe. Pipe is for water, not gunpowder. If you check the strength standards for steel pipe, you will find numbers such as 800 psi internal pressure, etc.

4130 seamless tubing is available in .250" wall and 2" ID from Aircraft Spruce online (and from others I am sure) at $20 a foot. This would be much more suitable for barrel use than pipe.

As I recall, punt guns were strapped to the boat (punt) and aimed by turning the boat. Elevation was fixed.

There is still a tradition of waterfowling in the UK using punt guns. wildfowling.com See the section on "The Punt Gun and Its Firing."

Double D · « **Reply #2 on:** December 05, 2006, 04:25:57 PM »

Ssorry, but I don't realy think that a Punt gun falls with in the scope of our board. The problem is I don't know where to put it. I am going to go on the Moderators board for some suggestions of where to put it so it might find persons who are a bit more knolwedgable o the subjet to help.

For right now the subject is open so post away guys!

jeeper1 · « **Reply #3 on:** December 05, 2006, 05:49:55 PM »

FWIW, I have a video of Tom Knapp shooting a punt gun on my computer. It's tied to a shooting bench but still kind of seriously recoils.

GGaskill · « **Reply #4 on:** December 05, 2006, 06:27:20 PM »

What about wall guns?

NitroSteel · « **Reply #5 on:** December 05, 2006, 07:26:16 PM »

Thanks for the reply guys. If it doesn't fit the board, then I'm stumped as to which board it would fit. I've seen folks post about hand "gonnes" (sp?) - hand held golf ball cannons. This is a boat mounted or heaven forbid - shoulder fired black powder cannon (basically). If it gets moved, let me know where to.

I'll look into the tubing at Aircraft Spruce, I actually have one of their catalogs at home. Is 4130 seamless the tubing of choice? As a rule, how do you determine the necessary wall thickness to barrell diameter, maximum powder load, maximum barrell length, maximum weight projectile, grade of powder (ffg?)? I used the mortar rules for my bowling ball mortar, but I assume this would fall under a different set of rules since the barrell will probably be 6 ft long and the projectile will fit tightly inside (much different than the mortar).

I can't wait to get started on this project.

Thanks again,

NitroSteel

GGaskill · « **Reply #6 on:** December 05, 2006, 09:07:04 PM »

I only list the Aircraft Spruce site because it is online. You should try to find a metals dealer with a wider selection of thicker wall tubing than AS has since you're not needing this device to be able to fly. If you want the tapered barrel look of a real punt gun, you'll need something that starts out pretty thick walled. You could use the .250 wall by 2 ID with an appropriate breech piece but you wouldn't be able to taper it. You should also get a flint or percussion musket lock for an ignition system if you are building a muzzle loader.

Just guessing from the picture, 1.5" bore and .75" walls at the breech, maybe 2" at the muzzle. You have to decide how much powder and shot and build to that. Be sure to check out the link at wildfowling.com.

Double D · « **Reply #7 on:** December 06, 2006, 05:53:21 AM »

Okay guys the punt gun stays...moderators agreed. So lets get to talking. Take pictures for us NitroSteel

Cat Whisperer · « **Reply #8 on:** December 06, 2006, 07:09:17 AM »

I was going to suggest the large bore rifle forum, but they seem to top out about 50 or 60 caliber.

Lookin' forward to the pix.

Rickk · « **Reply #9 on:** December 06, 2006, 07:20:20 AM »

ffg is too fine for something that big and that long.

I'm thinking cannon grade would produce lower (safer) pressures than fg and with the barrel length you are talking there shouldn't be any issues with incomplete powder combustion.

GGaskill · « **Reply #10 on:** December 06, 2006, 07:57:46 AM »

Agree 100%, for a 2" bore, Cannon grade all the way.

NitroSteel · « **Reply #11 on:** December 06, 2006, 09:08:47 AM »

Since my first post I've done alot of reading on the subject. It seems most punt guns were between a 4 bore and 2" in diameter. It looks like a 4 bore is just a touch over the 1" mark. I decided that it would be more appealing to make a real shotgun size than to go with something like "a 2 incher". In short I decided on the 4 bore.

I went to the junkyard today and got a 6 ft long hydraulic cylinder with a 1" inner diameter. From what I understand hydraulic cylinders are seamless steel tubes. I'll probably just use 5ft of it for the barrell and get a breach plug made and go from there. I can't wait... Once I get it together and tested I'd like to work DOWN some loads so that I can shoulder fire it - if only once...

Is the consensus that I should use cannon grade powder on the 4 bore also, what if the barrell is only 4 ft instead of 5 ft? How long should the breech plug be? What would be a reasonable load of shot/powder for a "cannon" of this size.

I'll post pic's of my BB mortar tomorrow. And will keep you posted on the punt gun as it comes along. Any ideas on firing mechanisms, etc. will be greatly appreciated.

Thanks again,

Nitrosteel

jeeper1 · « **Reply #12 on:** December 06, 2006, 10:05:11 AM »

Quote

Any ideas on firing mechanisms

In the punt gun video I have, it is percussion fired. Probably uses musket caps.
If anyone is interested in seeing the video email me at rlachance@wavecable.com and put 'punt gun' in the subject line.

Rickk · « **Reply #13 on:** December 06, 2006, 01:12:31 PM »

Now that you have dropped the bore to 1 inch, I would not be sure if fg or cannon would be more appropriate.

However, Cannon grade would be safer to start with. A 4 foot barrel is still pretty long. If the bigger grain size still burns mostly complete in 4 feet, you will have lower pressure for the same velocity, as it will use it up more slowly over the length of the barrel instead of peaking higher for only part of the ride up the tube.

One thing to be aware of... I learned it from personal experience... more than likely you will be dealing with loads that are not all that big, at least as cannons go. Cannon grade, and fg to a lesser extent, are hard to measure by volume. In smaller powder measures (100-200 grains or so range... maybe even a bit more) you will find that you are doing exceptionally good if you are even getting charges to fall within +-10% of a target value if you measure my volume. I now use a scale 100% of the time for cannon loads. I got sick of using a beam balance powder scale for this, and found a small battery powdered digital scale that measures in grains, grams, ounces, up to about 3.6 ounces. I think it ran about $65 dollars or so... about the same price as a good beam balance powder scale. I use a volume measure to pour out the first 90% or so, and then drible the rest in by hand.

GGaskill · « **Reply #14 on:** December 06, 2006, 01:24:37 PM »

I went to the junkyard today and got a 6 ft long hydraulic cylinder with a 1" inner diameter.

What's the wall thickness?

From what I understand hydraulic cylinders are seamless steel tubes.

I don't know this one way or the other, but I would definitely inspect the tube looking for a seam.

One inch diameter is the boundary for me between Fg and Cannon grade. Either should work OK, and with either, you have to be intelligent in the application.

Rickk · « **Reply #15 on:** December 06, 2006, 01:46:54 PM »

Here are some links to some good punt gun pictures / drawings:

http://www.thefiringline.com/forums/showthread.php?p=2113315

http://www.sinkbox.com/productdetail.php?Inv=456

NitroSteel · « **Reply #16 on:** December 19, 2006, 05:00:23 PM »

Okay, I finally had some time today to work on the "barrell". I put it on the band saw and cut through the tube. The external diameter is 2.25", the internal diameter is 1.75", wall thickness is .25" and the tube is seamless.

Having limited experience with my bowling ball mortar (which I've genuinely tried to post pictures of, but as it turns out my pic's are too large and I'm not sure how to downsize to that small), I know that the wall thickness of the breech should be the same thickness as the diameter of the bore. My powder chamber will be 1/2" diameter (leaving approximately 5/8" wall thickness all around. This being said, how long can the barrell be? Right now it is 5'3", I don't mind cutting a little off of it, or for that matter cutting enough off it to make it safe. I'm not planning on tapering it, but realize that it may (I don't know?) cause excessive pressure to build up if it is too long. I realize that the rules on a "cannon" state that this should be the thickness all the way down to the end of the barrell. I'm not building a "cannon" per say. This isn't practical for what I'm doing and I really don't think it's necessary either, but I'll leave it up to you to tell me that I'm wrong.

I know on my shotgun the thickness of the barrell is not nearly as thick as the diameter of the bore and it can safely shoot a tightly packed, hot and fast load - - - even a slug. I won't be loading excessive heavy loads, and nothing I use will fit tightly (similar to the bowling ball mortar, just with a longer barrell). Just thinking out loud.

Please let me know what is safe as far as length of barrell (assume I am shooting cannon grade powder) and shooting a golf ball, very rarely would I want to actually shoot it as a punt gun, there's just nothing to shoot at with a 1 bore shotgun). I'm really just wanting the look of the gun, the smoke, the bang, and the amazement of shooting a golf ball farther than Tiger can hit one or even see it...

Thank ya'll again,

NitroSteel

GGaskill · « **Reply #17 on:** December 19, 2006, 07:23:43 PM »

Barrel length will have nothing to do with maximum pressure. Powder charge weight and granulation and shot weight are the main factors in chamber pressure. The farther down the barrel the shot goes, the lower the pressure, so the barrel can get thinner to the point its mechanical strength limits it. In fact, if the barrel is too long, the shot will not exit because the pressure has dropped too much (I don't think 5'3" is that short.)

A 1/2" diameter chamber is pretty small. With a 2.25" diameter barrel you could go to a 3/4" chamber with no difficulty. I would recommend shrinking a 3" sleeve over the chamber area so you could use a 1" chamber. The sleeve doesn't need to extend more than a couple of inches past the front of the breech plug and you could taper the front if you prefer.

I would not bother with Cannon grade powder unless you make the chamber larger than 1" diameter. Fg should be fine, especially if you stay under 1".

I know on my shotgun the thickness of the barrel is not nearly as thick as the diameter of the bore and it can safely shoot a tightly packed, hot and fast load - - - even a slug.

The difference between your shotgun and your punt gun is that the shotgun was engineered of known materials to use a shell of known characteristics; your punt gun is SOP'd from unknown materials and experiencing unknown pressures upon firing. You are welcome to engage a Professional Engineer to design your punt gun but be prepared to pay for the work.

NitroSteel · « **Reply #18 on:** December 20, 2006, 01:59:27 AM »

GGaskill,

Thank you for the information. You cleared up alot of my questions and concern. I will get a 3" sleve made to go over the chamber area and extent about 2" out in front of the breech plug. Chamber will be 1" diameter and will plan on shooting Fg.

In regards to the breech plug, what is the best way to design this and "attach it"? Should it be threaded into the rear of the barrel, or be held in with 2 pins (much easier for me to do)? If so, what should the pins be made of, how thick should they be?

Thank ya'll again.

NitroSteel

Double D · « **Reply #19 on:** December 20, 2006, 06:21:16 AM »

Since this is basically going to be giant shotgun, i would build it with a screw in breech plug. You will need a tang any way to help stock mount it.

GGaskill · « **Reply #20 on:** December 20, 2006, 08:13:15 AM »

I would recommend a screw-in plug also since it will make cleaning much easier. The threading will be a pain; you'll need a long bed lathe, but once it's done, you won't have to do it again. Cleaning needs to be done every time you fire it.

NitroSteel · « **Reply #21 on:** December 20, 2006, 12:17:24 PM »

I don't have a lathe, but I have a friend/neighbor at the machine shop that will do it for me, however it always gets put on the backburner and usually takes 4 to 6 months to get done (but usually cheap/free)....

In regards to the "sleeve". I called our local steel supply company and checked on getting a foot long piece of 3" o.d., 2.25 i.d. seamless tubing. Well, the price was $120.00 for one foot or $180.00 for 5 feet. I declined. I started looking on the internet and couldn't find this tubing anywhere. I did however find a combination of seamless tubing that will work (building up the thickness).

2.26 id, 2.50 od
2.5 id, 3.0 od

I figured this would be fine since it is a tight fit and it is all seamless (I could even use it to give a bit of a contoured look without any real machining) and will be a combined cost of about $55.00 for one foot of each, plus shipping. Do you guys think this will work / forsee any problem with it?

Assuming I decide to go elsewhere to get my breechplug threaded (I'm impatient), what should I expect to pay? Does anyone else have a "pinned in" breach plug, are ya'll thinking this is unsafe for a reason, or just nicer to have it threaded?

Thanks again,

NitroSteel

Rickk · « **Reply #22 on:** December 20, 2006, 12:49:08 PM »

I've been shooting BP guns for 30+ years, and have never had a reason to remove a breech. You don't need to. If you can make a hooked breech to remove the barrel from the stock, that makes cleaning easy. Remove the barrel, remove the nipple, drop it breech first into a bucket of host, soapy water, and run a tight cleaning rod up and down and you will pump water in and out of the barrel. Flush with clean hot water and then run a few patches soaked in "moose milk" or whatever you want to call it (machine soluable oil) and you should be OK.

If you decide you don't need to remove the breech, either weld it or braze it. Welding should be a fairly low cost deal if you have to farm it out. You can braze with Mapp gas in a propane-type torch that can handle MAPP. If you weld, make the breech plug fit tight. If you braze, make it fit loose. Also, if you are brazing, make the breech plug longer... an inch or so at least. You won't be able to penetrate an inch deep by welding, but you can if you braze. An inch long brazed plug will be stronger than a 1/4 inch deep Mig weld.

If you sleeve tubing together, unless the fit is tight the extra layers will just be a blast shield when the primary tube ruptures (as our recent experimenter with thinwall found out).

CU_Cannon · « **Reply #23 on:** December 20, 2006, 01:12:28 PM »

I would go with the threaded breach plug. It would make cleaning and inspection much easer. It also leaves the option of trying different chamber sizes. If you have it welded up and find the chamber isn’t quite what you want you are stuck with it. There are also porosity issues with welded barrels.

From a strength standpoint the threaded plug should be the same as the welded if done correctly.

GGaskill · « **Reply #24 on:** December 20, 2006, 02:50:20 PM »

Regarding the reinforcing sleeve, I guess I have a different perspective since I have four lathes in my garage shop. I would drive to my local steel supplier and look through his rems (remnants) pile for a piece of 3" solid round as long as needed. This will weigh about 25 lbs and shouldn't cost more than $15 as a rem.

The hole through the sleeve needs to be exactly .003" SMALLER than the outside of the barrel (which needs to be truly round which seamless tubing usually is NOT) for a reasonably easy shrink fit process. If the sleeve doesn't compress the barrel when installed, it will not provide much extra strength. So you probably will have to machine the outside of the chamber area of the barrel until it is true, then bore the sleeve to the proper diameter for the shrink fit. A lot of work and PITA but the best way to do it.

I don't think pinning the breech plug is a good idea; not enough material doing the work. Also, the inside of chamber area should be bored since seamless is not perfectly round inside either and you want the breech plug to be a good fit (preferably shrink fitted also.) If you decide to weld, put a heavy chamfer on the back of the plug and the back of the bore and fill the V with filler rod. Combined with the shrink fit, it won't come out.

Paying a commercial shop to do this kind of work is expensive. I would expect at least $100 to make a threaded plug, $100 to turn the barrel inside and out, and another $100 to thread the inside. Lots of setup time for only single parts. Maybe even more. And finding someone who will work on cannons is usually pretty hard.

Double D · « **Reply #25 on:** December 20, 2006, 04:16:43 PM »

The outer reinforcing bands do not need to be seamless tube. Only the inner bore does.

NitroSteel · « **Reply #26 on:** December 21, 2006, 07:30:27 AM »

I think I'm going to do what GGaskill said. I actually checked on it today. To use the shops "remants" and make the sleeve and breech plug to specs it will cost a total of $110. $75 for the sleeve and $35 for the breech plug. I'll just plan on welding the breech plug in, I can't see paying $100-200 for threading this when it really isn't necessary. O.D. of the barrel is 2.25". For the sleeve I was planning on using a 6" long piece of 3" diameter roundstock. Having the 2.25" hole bored through the middle (only 5" deep), leaving the last inch as a backing. The barrell is 1.75" I.D. The breech plug will be machined to fit inside the barrell (2.5" long, with a 1" diameter hole bored 1.5" deep, leaving a 1" backing on the breech plug).

I will weld the breech plug in, then slip the sleeve over the whole deal and weld it (only place to weld will be to the barrell). This will leave 2" thickness on the back and 1" thickness around the "bore" 1.5 inches long - and for the first 3.5 inches of the barrell.

From there the ignition system is still a bit undecided, but have a pretty good idea of how to design a hammer on top with some linkage for a trigger on the bottom. A friend of mine loves woodworking and has already agreed to build a stock. Gonna do/get done the metal working for one that he is planning on making as soon as he finds a barrell.

Do you forsee any problems/safety issues with the design so far? Is it a bad idea to weld the sleeve to the barrell, will it weaken it? Would it be better to just JB weld the sleeve on?

I'm probably gonna go ahead and let the shop get started if ya'll think this is good. This is gonna be one heavy gun, for sure.

Thank ya'll again,

NitroSteel

Rickk · « **Reply #27 on:** December 21, 2006, 07:45:54 AM »

If you weld the sleeve to the barrel anywhere but the back (which is behind the chamber) it will weaken the barrel right where the weld is. It may be OK, it may fail. no way to tell for sure.

Welds should in general not be done laterally like that on any object. There are risks even longitudinally in a barrel.

You could possibly drill holes in the sleeve and weld thru the holes. The best place to weld would be in the back where there is no stress on the barrel. Maybe weld thru holes near the rear to get the best of both worlds.

Maybe silver solder would be better solution. It would not get hot enough to alter the base metal at all.

Not sure how to do it right, but I know welding on the front is not a good idea. Maybe someone else has a good solution.

Double D · « **Reply #28 on:** December 21, 2006, 08:45:44 AM »

Since there is no thrust to separate the reinforcing section from the thinner barrel i would epoxy the barrel and the reinforcing section together just as is recommended for installing liners in cannons. Put a single pin through the reinforcing ring and breechplug. You will also have to put a vent liner in and it can serve as second securing device.

GGaskill · « **Reply #29 on:** December 21, 2006, 08:50:05 AM »

The hole through the sleeve needs to be exactly .003" SMALLER than the outside of the barrel (which needs to be truly round which seamless tubing usually is NOT) for a reasonably easy shrink fit process. If the sleeve doesn't compress the barrel when installed, it will not provide much extra strength. So you probably will have to machine the outside of the chamber area of the barrel until it is true, then bore the sleeve to the proper diameter for the shrink fit. A lot of work and PITA but the best way to do it.

The whole purpose of the sleeve is to compress the barrel in the chamber area which means it needs to be a shrink fit. Gluing or welding will not accomplish this. That is why I went through the description of the machining processes above. The shrink fit will be more than adequate to retain the sleeve in position; welding is not necessary and gluing won't work because you have to heat the sleeve to red and slide it on the breech end of the barrel before it gets cold (the heat expands the sleeve enough to allow it to fit.) It is possible to just force it on with a big enough press but that is more of a PITA, especially with a 5 foot long barrel.

I would bore the sleeve all the way through so I could inspect the breech plug weld at intervals. Then I could reweld if I noticed a problem.