Sounds to me it needs a good strip & clean. Had a similar situation some years ago; sent the gun to Kirk Merrington. This one was so tight you almost couldn't operate the triggers! He measured the tighter bbl. at .054 constriction! As to the tight opening & operation; wot had happened was the vehicle in the grease as originally used had dried over the decades essentially becoming a solid. Removal of that solidified junk and lubricating properly once more was all that was required. I had him open the altogether too tight choke while he had the gun. It too utilized a helice grip lock; I gather that was fairly common on French SxS's once the VC patent expired, from wot few I've seen & earlier discussions here. Hope that you will post some pics for us.
