That is one fine shooter for the price....ya did good,only thing is from now on when you buy your next K-22 you will feel like your overpaying!!....oh you WILL buy more...he he he
late model 17-4s transitioned into the heavier barrel and the 17-5 continued it,
Your 17-6 is probably transitional as it has the 17-5 heavy barrel,
The early 17-6's probably used up leftover 17-5 barrels.
Your barrel has a wider and thicker barrel rib almost like a Model 19 without the underlug.
Also has a longer ramp base.
Here is a picture of the barrels on a K22 outdoorsman, K22 post war Masterpiece then the K22 Heavy Masterpiece.
The photo at the bottom is your 17-6.