Originally Posted by Southerngunner
From what I have learned in the last few days ever since I picked up my first Speed Six there is a difference in the early low back models built from 1972 through 1974 and some models were round butt and some square butt.
I could be wrong but I believe that the Speed Six's were round butt. Perhaps Iowegan can chime in with the correct info.
All Speed Sixes (to my knowledge) were round butt. Presumably for concealed carry.
Service Sixes and Security Sixes were square butt. But, as you point out, the backstrap shape was changed.
So, essentially there are 3 different grip patterns (possibly 4).
Square Butt Low Back for some Security Sixes and Service Sixes
Square Butt High Back for some Security Sixes and Service Sixes
Round Butt for Speed Sixes. Was there a high back/low back change for the Speed Sixes?
I have a Security Six with a set of Speed Six (aftermarket) grips that are oversized for the Speed Six. I had to relieve the inside of the grips for the square butt, but they work.
If you wanted to put a set of Security Six grips on a Speed Six, you probably could do it, but would want to shim or fill the inside of the grips (much like bedding a rifle action). But you take your chances that it will work well or look good.