I just acquired an H&R model 732. Can anyone tell me about this gun? Is this a double action only, or is it in need of repair?-- It will fire (with the cylinder removed) by pulling the trigger, but won't thumb cock. There is an odd little trigger-like device in the rear trigger guard that will drop the hammer from halfcock to firing position. i don't see a safe purpose in that. Any info would be appreciated. Thanks.