Colin;
One question from me, what is your bore diameter on these 2-bores. I don't recall if it was the single or not but do recall seeing about a modern made 2-bore & as I recall the bore diameter was more like that of true 4. Per the proof house charts a 2 would masure 1.325" with 4 being 1.052". I know that at least some of the early 4's built for paper shells were proofed as 6's. Since you said the "Ball" you were using for this gun weighed 3,600 grains I assume you are not using a spherical ball as such. Certainly way out of this ol pore'boys price range but interesting reading never-the-less. As a retired machinist model-maker I can certainly appreciate what all you had to do to build an item like this on a non-production basis.
