Roughly 1/2 scale Parrot Field Rifle

[Victor3]

The barrel is sleeved with a piece of 3" round stock and it is "sweated" on (the barrell is approximately 5 thousands larger than the hole in the round stock). There is no breech plug , and the is a minimum of 2 inches on the rear of the barrell and approximately 1" wall thickness around the breech area.  When using a "heavy" lead ball or bullet, should I be concerned about pressure (assuming I use no more than the recommended powder load of 2 ounces for each inch of bore diameter)?  Should I weld the sleeve on? The person at the machine shop didn't think welding the rear on was necessary, but he quickly said he was not an expert on cannons...

NitroSteel

 NS,

 You'll get differing opinions on this; most will probably say it should be welded for safety's sake. Personally, I don't think you're in any danger of the sleeve ever backing off, considering a .005" interference fit and the length of the joint.

 Might not hurt to weld it at the front of the sleeve, but be aware that if the barrel wall is thin in this area, heavy welding may reduce the bore diameter at the weld. I found this out the hard way after welding the trunnion ring on my 1" smooth-bore Parrott.

 I've built two cannons using heat-shrunk, blind-bottom barrel sleeves similar to yours, but both of those also have threaded/welded breech plugs. Not that it was necessary, but I wanted them that way.

[Double D]

Yes his barrel may have been made with DU in mind, but it was in a gun designed and built to fire bullets of DU.  This gun isn't built for the additional pressure and recoil the DU round would generate.  The lead projectile is also going to generate additional pressure and recoil in theses smaller lighter guns and will tear things up if not built strongly..

The Zinc rounds are also reuseable, they will be less deformed during loading, firing and impact.

Nitro steel, the Sleeve was made boring out a piece of solid round stock .005 smaller  and then shrinking fitting the barrel without fitting a breech plug?  You have a very great chance that you have created a pocket for corrosion to form. When the sleeve cooled you got a good shrink fit around the outside diameter of the barrel and the OD of the barrel.  But what kind of fit did you get at the bottom of the hole in the sleeve and the bottom face of the barrel.  I fear you have a seam there and over time corrosion will build and the gun could fail and harm your Grandchildren.  Remember we build these things not for us but the next guy to own it.

You definitely should weld the sleeve on and you should also be sure to put a vent liner in before you fire this gun to protect the seam between barrel and sleeve. 

This is a outside breech plug and is no different than an interior breech plug which is shrunk then welded inplace.

[Victor3]

"Nitro steel, the Sleeve was made boring out a piece of solid round stock .005 smaller  and then shrinking fitting the barrel without fitting a breech plug?  You have a very great chance that you have created a pocket for corrosion to form."

 I was going to mention that, but figured what's done is done...

 Could be modified by facing the rear of the sleeve off to the back end of the barrel and tapping for a 1 1/4-12 cap screw as a breech plug. Then it could be cleaned easily and breech-loaded if desired.

[Cat Whisperer]

I have such a cannon that has a removable breech plug.

The end of the plug has a copper washer that presses up against a shoulder - crush fit.