I have one of these "jam o matics" There are VERY ammo sensitiive, not 100% reliable, and the same comments were re interated to me directly from a Henry rep when I called to mention my issues. I had one of the Charter Arms versions also and they were even worse. They are a cool idea and can be made ot work better with a good deal of work.
There was a tutorial around a while ago that discussed this. The only thing I recall, was a mention of "throating" the barrel at the breech with some polishing compound and the head of a bullet, I think it was a cased 223 round if I recall.
It is a fun guy, just would not rely on it in a one shot life or death situation.
Nemo ME Impune Lacessit
Manus sapiens potens est