Hi<br><br>I have an 1877 Colt thunderer that will not operate in single action mode. The double action operation is perfect as well as the half-cock position for loading. However in single action mode, the trigger will not cause the hammer to move forward regardless of how hard it is depressed. Any suggestions as to the cause of this problem would be greatly appreciated. Any suggestions as to possible inoperable parts.<br><br>THANKS!!<br>TERRELL<br>