First, welcome to the forum.

There are a couple of problems with your post. If your gun has an "S" prefix to the serial #, you have too many digits in your post. There are no more than 6 numbers following the S. Check your serial # again, on the bottom of the butt. You will have to remove the goodyears to get to the serial number.

Second, the "1955 Target" is either a pre-model 25 or a model 25, not 26. We need the correct serial number to be able to tell you what stocks are correct for your gun.

Lastly, assuming you have a pre-25, I would strongly recommend you NOT chamfer the cylinders. It would seriously impact the value. Depending on condition, it could easily be worth $1200 to $1500. I can't see the value of chamfering, as the gun shoots .45 acp using moon clips. If you are unable to drop moon clips in the cylinder, chamfering certainly will not help.

Pictures would help answer your questions.

__________________
SWCA 3297 SWHF 583