I bought my Dan Wesson M15 about 11 years ago from the pawnshop and it shoot great single action but it will not fire double action ( light primer strike ) and I tried Federal primer, Winchester and CCI the misfire will be vary from 1 shot to all 6 shot and if I cock the hammer and shoot it single action all the round will fire. What part that I need to replace? and where can I obtain the instruction with picture on how to do it ?