Author Topic: Advice for my new mortar (Read 1253 times)

Pogue · « **on:** March 15, 2004, 03:59:15 PM »

I finally took the plunge and ended up trading some unused firearms for a cute little Coehorn mortar that had been sitting in a local gunshop as long as I can remember. It appears to be the one Dixie Gun Works used to sell. I found an old DGW catalog, and the descriptions match: 2 5/16 in steel lining in an iron barrel, OAL about 15 in, about 85 lbs total weight, etc. Now I'm ready to get it ready to fire (of course the guy at the shop wouldn't recommend that, but the DGW catalog says go ahead).

Obviously the first step will be to clean out the light rust from the bore. No questions about how to do that, being a long time muzzleloader.

Next step will be to finish drilling the 1/4 in or so of the vent. The current diameter is 1/4 in according to DGW, but that seems a little large. I plan on using cannon fuse, so should the remaining vent be drilled at 1/8 in?

Now onto charges. DGW says 1 to 2 oz. Any suggestions? Difference between blank and projectile loads. Is wadding needed?

And what about projectiles? I've yet to find any cans that are that exact diameter. A racquet ball is perfect, but I'd be afraid of getting it glommed in there should it melt. Maybe if I filled it with shot, and put a well Criscoed patch, a la a muzzleloading rifle ball around it???

Anyway, all inputs welcome on helping the newbie...

Cat Whisperer · « **Reply #1 on:** March 15, 2004, 05:02:50 PM »

Pogue - finding the right projo's can be a real search. You could easily make a mould - cut a cylindrical hole in a timber - line it with tin or plastic and pour in the concrete.

All of my morters, while not histerically correct are of standard sizes for commonly found boolets - golf balls, beer cans, soda pop bottles, and PVC pipe. Others include D-cells, OJ cans etc.

Let us know how it shoots!

Blaster · « **Reply #2 on:** March 16, 2004, 11:48:45 AM »

Hey Pogue.....glad to hear someone else has a mortar and is asking questions. That way I'll learn too and I have a lot to learn. I have a couple mortars. One fires a beer can loaded with concrete. The other one fires about a 2 1/4-in piece of electrical conduit about 5 inches long, also filled with concrete. I had contacted South Bend Replicas, (formerly Barneys Cannons) in Indianapolis and after hearing him recommend only about 65 to 70 grain of FG to start, thought I'd do just that. It is absolutely unbelieveable how LITTLE powder is needed for these mortars. I presume your's has a chamber which will be much smaller in diameter than the bore? You should get a lot of good responses regarding the firing of your mortar. Just be C A R E F U L and follow all safety procedures. Good luck with it and be sure to let us know how it works out! Blaster (Bob in CO)

Cat Whisperer · « **Reply #3 on:** March 16, 2004, 12:59:48 PM »

Conduit is a sleave that I'd not thought of - great uniformity, easily available!

Echo the concerns of starting with small charges and working up. If you have a really short barrel it will use much more powder than the longer ones.

I've got two different beer-can caliber mortars - both with bores about one beer-can long + 1/4". Range on them is 100-130 meters. My friend's DOM beer-can caliber mortar can reach out 400 meters using 1/3 the powder mine uses.

Pogue · « **Reply #4 on:** March 16, 2004, 04:13:05 PM »

I don't think I can measure the chamber volume until I complete drilling the vent. But it is the same diameter as the bore (2 5/16in), so I think the DGW recommended charge of 1-2oz will be necessary. I guess I can rig up a plug for reduced charges.

BTW, any inputs on the vent diameter? Keep going at 1/4in or reduce it to the 1/8in fuse diameter?

TIA

Double D · « **Reply #5 on:** March 16, 2004, 04:40:16 PM »

If you are drilling into Cast iron and then into the steel liner you are going to want a vent liner. If you don't install a vent liner you will end up with black powder fouling building up in the vent between the tube liner and the cast iron. This area will corrode, rust and make weak spot that can blow out bursting the gun.

If you go down to the post The More Complete Cannoneer http://www.graybeardoutdoors.com/phpbb2/viewtopic.php?t=18455 you will see what a vent liner looks like.

Blaster · « **Reply #6 on:** March 17, 2004, 06:55:35 AM »

Cat Whisperer: Just curious as to how many grains of FG you are using for your beer can size mortar? I presume you are merely dropping the charge into the chamber loose or are you wrapping the charge in aluminum foil? Thanks! Blaster (Bob in CO)

Cat Whisperer · « **Reply #7 on:** March 17, 2004, 01:33:38 PM »

Both of my beer-can caliber mortars are coehorns. That is, there is a powder chamber with great thickness of metal around it that contains the charge and then the walls of the bore can be made much thinner and lighter. I've never weighed the charge. But filling the powder chamber would be between 1/2 an ounce and an ounce of powder.

Take note that both are extreemly strong. My first one I cut from a billet of hot rolled steel - the other cut from 5" diameter of 4140 tool steel (prehardened state). Both much stronger than cast iron, less brittle too.

When I was first test firing my 4.5" mortar I started with one then two and finally 3 35mm film cans full of powder under 7.5 lbs of concrete filled PVC pipe. (It also is made of 4140 - which is what rifle barrels are made from.)

If you use aluminum foil, you'll need a method of getting it into the powder chamber and of course a pick to puncture it.

I have seen pieces of fuse still burning some 2 minutes after firing - in the bottom of the bore or in the fuse hole. Clean well, swab and wait.

Cat Whisperer · « **Reply #8 on:** March 17, 2004, 01:38:09 PM »

Also - I generally use FFg or FFFg. Which I would NOT do with a cast mortar. The pressure is higher, but I've over built for it and have VERY short barrels. The barrel lenght on my two is 1/4" longer than the can. With a friends mortar (24" barrel) Fg or Cannon grade is much better - more efficient, slower burning, greater range, less noise and smoke.

Blaster · « **Reply #9 on:** March 17, 2004, 02:32:24 PM »

Many thanks for the info on your two coehorns. That's what mine are too.
I should have been out shooting mine today since it was 80 degrees here.
I'll have to post some pictures of mine when I have a chance to "wade through" the instructions I have for picture posting. The powder I have always used has been cannon grade or else FG. Blaster (Bob in CO)