This is a 1933 era pistol, with the firing pin in the frame, and a flat hammer face. Problem is it hits the .22 rim too soft and often misfires - leaving shallow dents on those rounds that do fire.

The firing pin moves very easily, without drag, and can be manually pushed out to about .050" with a flat instrument from the back. The hammer, pushed forward, only has travel to push pin out to maybe .030". I know the pin depends on the hammer to impart momentum to the pin to do the job. But the light rim dents suggest this is inadequate. The cylinder is tight, without front to back play.

The hammer does not hit or stop on the frame. I guess my question is, can hammer fall be increased to allow more like .040" of firing pin protrusion? I suspect this should be safe, as the rim dents are way too shallow now.

So, since the hammer isn't stopping on the exterior frame, what limits hammer fall at the firing pin? Is there an internal surface/notch or such that limits hammer fall?

I dont think so. I think it travels till the firing pin bottoms out. It sounds more and more like a weak mainspring.

I'd stretch the spring a bit and see if it cures what ails you.

With the hammer pushed as far forward as it can travel, there is still a gap between hammer face and frame of about .025", with the pin visible sticking out the rear of the frame. But like I say, the pin can be manually pushed out to about .050".

Also, I took a closer look, and the hammer can only push the pin out about .025". So something limits hammer fall so that it can't bottom out on the frame.