After doing a thorough cleaning as suggested, if it still drags, try the following.
Take the barrels off and put in a couple of new shells that you usually use. With the barrels held steady, take a good metal straight edge and place over the shells. With a strong light, look to see if the shells are not a tiny bit proud of the breech.
This has been a problem for more than one gun. It is usual for a man to close his loaded gun with a bit more force than he realizes after he loads it. We are usually more gentle , with these older ladies, when we close them empty.
It just may be that a proud rim drags when you open the fired gun for you will open it more gently.
A simple change of ammo or reload cases will solve the problem.
Best,
John
