Here’s the picture I copy and pasted from double guns that helped me out showing mine and your Deeley style fore end lever patten was in 1873 for the Deeley I was told.
It’s been a while or I should say a few years since I’ve messed with that gun probably a good three or more. If I remember right, I didn’t shim it with a piece of metal. I just stuck a piece of duct tape where I have a circled. It locks up super tight when doing so eventually I’ll have to shim it. I think in aluminum shim that I had which I tried from a pop can was too thick. Don’t remember maybe I did stick an aluminum shim in there. It’s been a while. I’ll have to look. Just depends on how loose Andy even your mating surfaces are. I remember Larry Potterfield has a video up on YouTube about it.
I’m gonna load up some shells for it later today. Going to add a plastic shot cup and some buffer to my proven 100 grains of Fg and 1 1 5/8 oz of shot turkey load to see if I can tighten up my shot pattern. It recoils like a 20 gauge/light 12 gauge trap loads with the load the way it is now so I have ZERO worries about modifying the load with buffer and a shot cup. If I don’t get good enough patterns, I will probably add one and 7/8 oz shot to my load. Imo I’m WAY under pressured vs some of the modern smokeless loads listed in the sticky here for Damascus. I’ve tried up to a square load with 1 5/8 oz of shot with 130 grains of FG. I’m sure a 100 grains with a 1 7/8 oz (or even 2 oz of shot for that matter…i don’t plan on trying a 2oz load) will be less recoil and less pressure vs the 116 grains of fg powder and 1 5/8 oz of shot square load. If my patterns look promising I’ll even down load with 90 and 95 grains of FG to see if I can tighten up my pattern even more. I’m just not impressed with any loads I’ve tried so far that I’ve tried out of it yet because the pattern spread out so much.