Well, you can pretty much eliminate the cocking effort from compressing the main springs if it is difficult to open whether fired or not. I think a good place to start would be checking the mating surfaces of the hook and hinge pin for roughness, galling, or lack of lubrication. Old dried up grease can cause a surprising amount of resistance to free movement. Check the mating surfaces of the action knuckle and the forend iron for any roughness and old congealed lube as well. This area also needs a little lubrication.
This is all stuff that you don't really need a gunsmith to look at. The subject of correct hinge pin lubrication has been beaten to death for years here, and opinions are varied. We are opening a gun, not spinning hot turbocharger bearings at 10,000 rpm. I like a little Mobil synthetic grease, because it is good stuff, and I have plenty on hand. Unlike oils, it isn't as likely to migrate from the metal surfaces and soak my wood. Make sure to use a solvent to clean and remove any old lube. This is just regular gun cleaning maintenance, because old lube that gets contaminated with dust and grit becomes a grinding compound that will actually accelerate wear.
