Rev war prototype needed

[accuratemike]

A while back I decided to build my first cannon (well, second if you include Jr. High shop class). At the time I looked around and decided it would be easiest to build a "pack parrott". Straight breech and maybe a simple taper. I bought a chunk of steel, 18" long-1.75" ID-4"OD. To get a little experience (and because I had a fitting piece of steel) I built the scale Gribeauval. Since then, my son and I have started reenacting Rev War. Our group has a local "home turf" where we can do what we please (including firing our cannons and mortars). I'm glad I picked the Gribeauval to be my mortar, but now I think I'd like to do something scale Rev War with the bigger chunk. I'll have an OD of 4" and an overall length of ~22" (with backplate and cascabel) to work with. I saw a "full scale British 1/2-pdr" listed on SBR's (?) site that is around the right size, but no picture. I'm sure others would scale to (or near to) my chunk. I would like to make a field piece and had my eye on some 19" wheels when I was thinking parrott. Keep in mind this is NOT for reenacting, but it would be nice to build something from the right period.
Does anyone know of a good pic I could work from ? I'm still saving my nickels for "Mueller's Treatise on Artillery" (I have a full scale "Galloper" with Verbruggen tube in my dreams) so I am not really shopping for books right now. The Gribeauval is testament to my ability to scale from an image with PhotoShop and a caliper. I'm not looking to make an exact reprodiction, more like "stand-off" scale. These pieces are are for getting the feel of things while I work twords something we can take out with us. (Mostly for fun)
I have the aforementioned tube, 1" plate for the backplate, some 2" for the breech plug and trunions and hitch ball cascabel all sitting here. Any suggestions? Any good (shot perpendicular to the tube or a drawing-thanks George for the Gribeauval) images out there? It is winter now and I could spend some AutoCad time to while away the long nights.
Thanks in advance, MIKE

[GGaskill]

... so I am not really shopping for books right now.

If you haven't bought a copy of Round Shot and Rammers (the source of the Gribeauval mortar drawings), you should, in spite of your comment quoted above.  It has a lot of coverage of that period including British, French, American, Spanish and Swedish materiel.  A Swedish four pounder would be something out-of-the-ordinary.

By the way, from the British table on p. 42 (RSaR) a full size 1/2 pounder would be 3' long, weigh 165 lbs and be of 1.58" bore.

[accuratemike]

Interesting, it was CannonLtd. that showed the  "full scale British 1/2-pdr" at 24" & 70#(SB31) (not SBR). Maybe I should do a 1/2 scale Verbruggen and a little Galloper. They show SB33 at 40" long. Maybe that is erroneous too. Santa is poor this year, I may still ask him (her) for some books after all. Thanks, MIKE

[accuratemike]

Drawing from Caruana's grasshoppers & Butterflies. Fig 2, Lord Townshend's Light Infantry 3 pounder (pg 6). From Muller: "The length of a gun is always reckoned from the hind part of the base ring, or beginning of the cascabel, to the extremity of the muzzle". This gun is 36" long, full scale. If simply halved, the breech is 3 1/2" in diameter. Having a 4" OD chunk (1.75" ID & 18" L), I expanded the diameter (~14%) and left the length unchanged. Now I have a 4" OD tube that will be 20" overall, with the cascabel. This pic is of the half scale drawing and chunk.



Now to make alot of chips. MIKE