One's an old H&R 922 and the hammer simply doesn't poke through the hole far enough. It looks like someone messed with the tip. I figure I could build it up a hair; I only need a tiny bit. The spring is fine. I have two other 922s and have owned maybe 7-8 more and it's just as stiff on this one. It strikes the same on every shell, from the look of the dents; they aren't quite as deep as they need to be, causing irregular performance. The other is an old H&R Young America with the same problem, a messed up tip-end of the hammer.
BTW: Both of these guns have solid, one-piece hammers, no floating pins or anything.