New and need advice

[pmmarionneaux]

I am interested in purchasing a mortar but with all the choices out there I am confused. I am interested in a soda can size mortar for making some noise and of course launching some cans. Does anyone own a mortar built by Cannon Mike. His prices are about 1/2 of others. The vent/fuse hole is not drilled through but that should be easy to complete. Ii do not care about historical accuracy...just want to have some fun. Can anyone help?

[Double D]

Have looked into having one made?

Get a set of beercan mortar plans. Go to your local Machine shop, have them make you a tube.  Build the bed yourself.

Historical accuracy isn't all that important, it's historical similarity that makes thes guns legal.

[Cat Whisperer]

pmmarionneaux -

The dellema of where to start.  Consider two things first:  what and where to shoot.  Ammunition is as much a consideration as where to launch.

If you only have access to 100 yard ranges, that's OK - the nationals are shot at that range.  (We're talking 4.56 and 8" diameter).

If you have longer ranges (open fields are good) you can still see the things hit out to about 300 yards or so.

I started by making a beer-can caliber mortar.  Fired on the 4th of July 1975 - on the 200th anniversary of the first shot heard 'round the world, but about 20 miles west of the bridge between Lexington and Concord.

Golf ball mortars are fun - they hook and slice just like I do.  

The 'hand-gonnes' (12th century) small often pole mounted mortars are fun to shoot but tough to tell what you've hit.

I haven't yet tried a small cannon, that may be next as I have a 1-7/8 bore Napoleon that needs to be exercised.

The big one (on the left) is 4.5" and shoots 4" pvc pipe filled with concrete out to 350 yards or so.

Look around.  You will find something that you HAVE to have.  Then compare prices, quality and the option of making your own.

ONE thing comes first:  SAFETY, quickly followed by keeping legal.  Do your homework, there are many things to read listed on our site.

AND WELCOME!

[Will Bison]

I agree with Double D, you can have one turned at a local shop. Get some rough plans to show a machinist for an estimate on cost. Check for metal/scrap dealers locally for raw material. Take a look at some of the photos on this site for ideas.

[pmmarionneaux]

If you were building a mortar what type of metal would you use. I have access to brass, carbon, and stainless. I was thinking brass for the look but not sure if it will handle the load. Any suggestions on what metal to use.

[Cat Whisperer]

Brass for looks.

If I remember right, N-SSA requires cast barrels to be lined with steel.  They don't say which type other than seamless and 3/8" thick.  And there are other requirements they have regarding welding.

I tend to overbuild.  A few mortars I've made were from CRS (cold rolled steel - 1018), one from a mystery billet of hot rolled steel, and the rest from 4140 for extra strength.

4130 has about the strenght of 4140 and you can (IF DONE RIGHT) weld to it - it MUST be preheated and such if you don't want it to crack.

Your design will dictate to a large degree the strength you need, hence the material you use.

[Double D]

Use Hr or Cr what ever you can get.  Send  me a PM with your adress and I'l send you a sent of plans for the popcan mortar.

[pmmarionneaux]

I would not be casting...I would be machining from solid piece of metal. Do you think it would be necessary to line the brass if I used it.

[Cat Whisperer]

Assuming a cannon.

1. The N-SSA requires a steel liner if you want to fire in their competition).

2. The cannon (1" bore) that I saw (at about 15' distance) explode was bronze and did not have a liner.

Yes, I would line a brass/bronze cannon with a healthy seamless steel liner.

[Calamity Jane]

There's two problems with brass/bronze that makes a steel liner mandatory for safety.

First, brass and bronze have very low tensile strength and poor resistance to shock loads. Brass and bronze have a tendency to SHATTER under shock loads - good for a grenade but poor for a gun!

Second, in building a cannon, you want materials of KNOWN properties so you can depend on its strength and mechanical characteristics. Brass and bronze are not manufactured to provide consistent strength, impact resistance, etc. - they are manufactured to control other properties that are more desirable in thier normal application.

Although you can pick up a piece of junkyard steel for a liner, I would STRONGLY recommend that you pay a little more for a piece with KNOWN properties.

I used 1061 structural steel (seamless) tube for my liner. Knowing the liner was strong enough to handle the loads, I used "bearing bronze" for the barrel because of its machinability and beautiful mirror finish.

[2oakes]

I see that in many Coehorn designs, the trunion bar at the rear is often welded into a milled recess. I have seen a version where most of a hole is drilled through the breech and the trunion bar sits in there without welding. http://www.brasswithclass.com/mortar_sled.php

Two questions:

1) Is this a good method to avoid welding problems with certain steel alloys (see quote below). It would seem that as long as sufficient thickness is maintained at the breech, it shouldnt affect safety, and it certainly wouldnt come apart.

2) It this modification sufficiently like a "replica" of a historic Coehorn to maintain its legality as a non-destructive device?

4130 has about the strenght of 4140 and you can (IF DONE RIGHT) weld to it - it MUST be preheated and such if you don't want it to crack.

[Double D]

The method of construction has nothing to do with it being being classed as a destructive device.  It's the replication that get's it exempted. If it looks like a coehorn and shots like a coehorn, it's a coehorn.

Depending how big your mortar is or how big your trunion is that is going to be a tough hole to drill.  Can be done but a lot of work.

Also drilling  an hole is going to require a longer tube and/or shortened bore/powder chamber.   The Trunnion will still need to be welded in place.

I would have no qualms about turning a cannon tube from a piece 1018.

[Cat Whisperer]

I generally agree with DD.

On the mortars I make, the trunions are bolted to the tube with two bolts offset to very near the edge of the tube.  This way the strenght is very good and it gives a good clean line between the trunion with no welding.

If anything my intent is to clearly overbuild.  This comes simply from fear, having seen a cannon explode up front and personal.  DD's recomendations are certainly reasonable.

Somewhere on this forum are jpg's of the cad drawings I used in making my 4.5" coehorn which show the dimensions and locations of the two bolts holding the trunion to the tube.

Welding is of course a viable option.  I chose to sidestep the issue completely (as I use 4140).  I would recommend though, that when you weld you use a certified welder - that way you know it's done right.