Rebounding hammers rebound back to the position where the sear rests in the safety bent, there is no half cock as such. This safety notch also prevents accidental discharges and should be checked for function.
In my experience the most likely problems (and I had them all one time or other) special to hammers guns are worn and defaced firing pins and their springs, stock cracks under the locks, corrosion damage to the locks, and about half the hammer guns will not open when the right hand hammer is cocked, which can be a disadvantage in certain situations. Cheap hammer guns tend to be hard to cock and this is expensive to fix.
The best buys, in my opinion, are round bodied peninsula back action rebounding hammer doubles. They are the simplest, most rugged and often the best balanced and they are easy to fix too. Over the years I had to learn to make firing pins, repair stocks, and even put a couple back on face with minimal equipment, and if I could do it, anyone can do it. The other advantage of hammer guns is the because they are simple, and easy to service and repair they seem to survive better than self cocking doubles so you can find a really good buy..
My current project is a Cogswell 410 weighing 1.9 kilos, that would be 4.4 lbs, and it shoulders fast. That is a fun double to handle.
