I took my Boswell to a local gunsmith to check out the loose action. He commented that the degree of movement when the gun barrels are moved laterally with the forend off is quite minimal. Considering the amount of use I give the gun, he said it will be many years before it becomes an issue. He suggested using light trap ammunition as a means of extending its life further and applying grease to the hinge pin. He replaced both firing pin springs as I've had an occasional misfire, mainly when using reloads. The original box lock springs were considerably more closed at the open end compared to the new ones he fitted. Thanks to all for your input.
So your problem "mainly" started with reloaded shells. You may have identified your real problem before this long effort to fix your gun. Be aware you can over seat a primer when you seat them. Look at the hulls that fail to fire. Is the primer seated properly or has it been over seated. With my Spolar I had the hydraulic cylinder adjusted so the shaft traveled too far by about 1/4" which caused me to over-seat the primer if I stayed at the bottom of the cycle too long. Pressure, over time forced the primer too far into the primer pocket. Go fast and it never did it, but if I stayed at the bottom of the cycle, several extra seconds, it would. This was on brass headed shells and never the steel headed shells. I had adjusted my cylinder longer to better seat primers in those steel hulls and it caused a problem in the brass headed hulls later. I no longer load any steel headed hulls like Remington game or promo hulls. You can even see the base of the shell is dipped in slightly.
I also had this happen with a MEC hydraulic loader once when I had a buildup of crud in the primer seating station. The newer, multiple part MEC primer post system works fine unless it gets crud in it. Some primers are flatter than others and can naturally over seat in certain hulls. If your problem was mostly with reloaded shells make sure they are not the real problem.
