Sunday, July 6, 2014

SP101 Cylinder Mods

My followers may remember the action job I did on my new SP-101, you can see it here

The gun shoots amazing, the trigger is smooth and the reduced power springs make a big difference.
Well after shooting the gun a bit I noticed the chambers were a little tight and the entrances to the chambers were a little rough.
I decided to polish the chambers and chamfer the entrances.

The first step (as with most modifications) is dis-assembly. 
Because you do not want to take any metal away from the extractor star, I had to remove it.
  As soon as I had the cylinder off I ran into a snag. The SP-101 has a different system to retaining the star extractor. The screw has a hole in it and requires a special bit.
Thanks to youtube I was able to find out how to make the bit. I started with a #3 hollow ground slotted bit
Using my Dremel tool, I cut a slot down the middle of the bit.
Before you go thinking I will never need this tool will also work for your Ruger Single Action cylinder pin retainer.
Important note! When removing the screw, remember the threads are reversed, righty loosey (turn clockwise to remove).
With everything apart I could begin working on smoothing the 90 degree edge on the chambers.
I used a half-round needle file.
You can see the file marks and how much material is removed, very minimal
Next I wanted to clean up the file marks and polish the inside of the chambers. I used this handy mandrel, I wrapped it with 320 grit paper until it barely fit in the chamber, then chucked it in my cordless drill. I then repeated with 600 grit.

I then used my Dremel again to polish the chambers with some buffing compound

Here is the cylinder after polishing

A little clean up with some Hoppes #9 and time for reassembly.

The cartridges now enter and exit the chambers much easier.
The whole process took about an hour, including making the new screw driver bit, and cost next to nothing.