What metal? Mild Steel? Bronze????

[willysjeep134]

1) how would one calculate the barrel thickness needed for a 10 gauge short barreled hand gonne? I'm thinking it should be similar to a 10 gauge shotgun or musket, but I haven't the fogiest idea how to calculate how much of what I really need.

The plan is to make a 10 gauge, 10" long hand gonne. I was thinking a powder charge in the neighborhood of 70 grains and no more than a 2oz projectile would be about right for a maximum load, just off the top of my head. So, where would one learn how to calculate barrel dimensions for shoulder arms?

[maddmaxx]

Don't know the calculations, but if you buy a barrel blank fron Gun Parts Corp, that work has already been done. They have  some 12 ga. blanks unturned and unchambered with a wall thick enough to bore some and still be on the safe side. And they are nitro-steel, so they are strong. They are also a really good price. If I remember right, around $10-$15 for a  blank 19"x1.150" od.x .729" id. Happy Huntin'

[Cat Whisperer]

The calculations include figuring hoop strength (among others).  It requires knowing the stresses to be encountered, safety margin and strength and shape of the material.

My preference is to massively overbuild.  Comes from fear & having seen a cannon explode up front and personal.

Isn't 10 ga about 0.750" diameter?  You probably could get away with 1/4" but I'd go 3/8 to 1/2" wall thickness of 4130 or 4140 steel.  Build a powder chamber of the right size for extra strength.

There are formulas and rules of thumb (like in thickness in diameters of the bore) listed in the beginning of this forum that simply specify 'steel'.

[Cat Whisperer]

Some of the issues you deal with are where and how severe the stress points are.  For instance on the inside of the bore at the bottom, do you have a rounded corner or a sharp corner - the rounded one is much stronger!  In the same regard, a small, deep powder chamber gives you additional steel thickness where it counts.  If you cut the 'iron from one piece of steel with no welding, you have little to complicate the design like strength of threads and potential of cracking of welds.

A general rule of thumb I use is to look at what other PROFESSIONALS are doing and overbuild that.

[willysjeep134]

Actually, hearing about barrel blanks being available cheap, I might look in to getting one and just threading it for a hook tang and fitting it to my CVA Plains Hunter caplock stock instead. All I'm looking for is something to play with that I can say I made. I'm thinking that if I can find a shotgun barrel blank that approximates the outside dimensions of my rifle barrel, the bore diameter isn't really that critical as long as it is a shotgun of some type.

Otherwise, a half inch of steel should certainly handle a light shotgun type load I would think. Most modern smokeless 12 gauge barrels are about 1/5 thick. I think a half inch should be safe. Thanks for the advice about profiling the breech too. I was thinking a suficient "cup" machined into the breech plug might help a little

PS. Here is a site I found extremely useful, and I got to learn some cool jargon.
http://www.weights-and-measures.com/xcombulletgage.html

[Double D]

Just a reminder gentlemen, this is the black powder Mortar and Cannon forum.  We have accepted hand gonnes, but muzzle loading shot guns don't fit....so if you wanna stay on topic while discussing muzzle loading shotguns apply their construction to the building of hand gonnes...a modified hooked breech made to fit on the end of a pole might work to make a hand gonne from a shotgun barrel.