Re: Jennings J22....
I filed a slot in this one for the extractor to fully seat in the barrel breach, and also filed the chamber opening flat to increase headspace. I just took it out and shot about 10 clips full through it. With high velocity ammo it shot very well and many clips with no jams. The standard velocity ammo had some jams, i.e. the ammo with the black/blue colored lead tips. The ammo with the yellow or orange lead tips worked well.
At least it's a shootable gun now. Before it was basically a single shot with a 6 round clip, and I had to dig out the shells after each shot with a pocket knife.