Here's some information and pictures on how I optimized my Ruger GP100 and SP101 for shooting lead bullets, which might be helpful to other shooters. It could be a long post overall, so I've broken it into two parts and please note that I won't intend to cover every step of the process, but will just hit the highlights.
Part 1 will cover recutting of the forcing cones, and Part 2 will cover reaming of the cylinder throats and then show targets shot "after" both steps were completed.
Before I get too far into this, due credit has to be given to a fellow named Iowegan, the resident gunsmith over on
www.RugerForum "dot net" and "dot com"(in the gunsmithing forums), as it was his IBOK that first inspired me to complete these projects on my GP100 and SP101. I got an informative e-mail response from him and also found several of his online posts which helped with many of the "how to" details, as well as some online info for the various tools used. As my late father would say, you have to be very careful as the metal take-off tools work much better than the metal put-back-on tools! So if you have any doubts about your abilities to do these tasks, it'd be best to seek help from a pro. For me, the challenge and research needed to "do it right", and by myself, is a part of the fun of such a project. But proceed at your own risk...
The "before" condition of both revolvers showed some machining marks visible in both forcing cones and undersized cylinder throats for the 0.358" lead SWC bullets I am using. The net results were excessive leading with mediocre accuracy at 50 feet, and I finally decided it was time to improve upon that reality. Let's start off with some "before" pictures of the forcing cones.
Here's the GP100 before:
And the SP101 before:
The 11-degree 38-45 Basic Chamfering Kit (#080-479-451) sells for $80 from Brownell's, but I obtained a used set (in very good condition) on GunBroker for about half that, and downloaded the instructions from the website. The cutter was very sharp, but the kit was complete and the Brownell's instructions and Iowegan's e-mail told me all I needed to know to do a decent job with this tool.
Here's a picture of the 11-degree cutter in my SP101:
Plenty of cutting oil and a smoooooooth cutting stroke were used, and I stopped frequently to check on the progress -- carefully cleaning the cones and tool of any chips. I used a steel millimeter ruler to check on forward progress, estimating "how many mil's left" till I overcut the original cone and this worked out well, using the slot in the cutter as a reference mark.
Forcing Cone Ruler:
Well, here's the cut forcing cones after using the tool. This picture (with the GP on top) was taken before I lapped the cones using the 11-degree brass lap with Flitz.
GP-SP Forcing Cones after:
OK, they look good, but did it help?
Stay tuned for Part 2...
Old No7
