It really depends on the application - a handgun of a certain caliber that's good for self defense may not be well suited for varmints, and vice versa. As stated earlier, I'd recommend going to a local gun store and chatting up the employees to get an idea of what suits your particular...
Are her hocks swollen? Redness/tenderness?
Something similar happened to one of our pullets not long after we first brought her home; she just started holder her leg close to her body and limping/flapping around. Comparing one hock to the other, the right one was quite swollen and very red...