I checked my bisley 45 convertible today. It's given me no trouble at all, however the fit left something to be desired when i got it new. The hammer was dragging terribly on the frame, basically didnt look too good. And the hammer pin was rotating, could not stop it, even tried loctite on the pin, still no good, frame to hammer pin fit was very ,very sloppy. Tried different hammer pin and different extended grip frame screw and still no good. I actually had to drill and tap the frame, and put in a set screw to prevent the hammer pin from rotating, and still used the extended grip frame screw. The mag research BFR I have uses a set screw like this, which is where I got the idea from.
Regardless the hammer cross pin does slide right out, however once again i find the end furthest from the plunger making contact with the frame opposite the plunger and this side of the pin was smaller diameter and appeared to be worn and rounded. I think the location of the plunger (being offset in the hammer) may tend to push the pin toward the other side of the plunger but im not sure about this. I do think on a double action the problem will likely be non existent as the hammer dog is centered in the hammer. Anyway, I again beat the pin with hammer a few times on a pair of pliers to increase the diameter on one side, and pushed it in from plunger side of the hammer. If you choose to do this, just remember in the event you have to remove the pin, push it out from the correct smaller diameter side.
There is enough play and side to side movement in some situations of the cross pin within the hammer (in my opinion) over time to potentially wear the pin and bind the plunger if it gets misaligned. Mind you we are talking about the hammer falling thousands if not 10's of thousands of times in my estimate to ever cause a problem in the worst cases, but in my opinion the risk is still there over time.
I'd say the pin itself needs to slightly longer in all the hammers Ive seen to make this event more unlikely or possibly to prevent this from ever happening. Increasing the diameter of the pin on the side closest to the plunger and pushing/hammering it in from that side might be better idea. This way it is very unlikely if not impossible to ever cause problems with binding the hammer plunger as it cant push through to the other side of the hammer (after wearing or whatever) and misalign or snag the plunger. The wear of the cross pin will likely be much worse if the frame to grip frame fit is off at all, especially the side opposite the plunger as this gives the pin a surface to catch on.
There might be other problems that lead to failure of a ruger single action prior to this happening, but I dont see many other possibilities. The only other big improvement id like to see on ruger single action would be to use heavier (where it meets trigger) or forged pawl, I think both would be big improvements and both changes would make an already excellent design nearly indestructible, and this post/poll would likely not even exist.
Edit...and fitting the transfer bar to the hammer better, so the hammer hits the frame at the same time it hits the transfer bar to avoid pinching and over stressing the transfer bar. Ive seen that mentioned probably on this forum, an excellent idea.