For many years Ruger produced a line of revolver that ended in 6: Speed 6, Security 6, Service 6.  They were the precursor to the GP100 and Sp101. As usual with Ruger, they are rock solid.  In some ways, they are a little easier to get inside of than the modern revolvers.   They only drawback for custom work is that they do not use a coil spring for the trigger return spring.  This makes tuning the trigger a little harder, but replacement...