Pete;
In 1954 at age 16 I bought my first double bbrl'd shotgun, a J Stevens Arms & Tool Co, model 325 if memory serves me correct. After using it a few months one day I pulled the rear trigger & it fired both bbls. I didn't have much money for a gunsmith, so first pulled the stock, it had a through bolt. A study of the innards revealed the tail of the right sear sat a little higher than the left one. There was also enough slop in the pin holes they could get togther, so if the rear trigger was pulled first the possibility of lifting both sear tails was strong. Now I was a farm boy, didn't even know at that time what a schematic was but thought this needed fixing, so I started pulling parts. The was a space between the sears where the pin went through & ball point pins were just getting popular on the market & usually ran out of ink after about a page & a half, so I popped one apart & but the little coil spring between the sears around the pin to keep them pushed apart. 5-6 years later I traded it off, but in so far as I know it may still be out there firing one bbl at a time with that "Bic-Fix" still working.
Moral is; A J Stevens is not really very complicated. If a 16 yr old farm boy can take one apart & put'er back together without a schematic, You almost certainly could to. I have no idea where you might find one. I have a Stevens parts catalog from about 30-40 yrs ago but it doesn't go back enough to cover those.
