I was asked as to the procedure to complete this job, so I'll go out on a limb here for all the adventurous/frustrated people with one of these guns, which really are super quality pieces otherwise. Let's put it this way, it's better to have too much steel in the cylinder, and then be able to correct it, than to have too little to start with.
The procedure is really straightforward. The key is to go slowly and carefully understand what you're doing with the reamer. You are enlarging the chamber diameter and depth within each cylinder charging hole to SAAMI sporting spec, but you are NOT cutting the recess for the cartridge rim. You might square up the recess a bit, but that's optional and if done incorrectly gets into headspace issues, so I'm not going to deal with it here. Suffice to say, follow the instructions below and you should be fine. If you muck it up by not being careful/being a Bubba, well, I have to refer you to the ancient Greek saying, "know thyself". If you have mechanical aptitude, this is a piece of cake, but some people just don't have that. So, Know Thyself before attempting. I disavow any responsibility for hamfistedness. That said, truly it's really very easy.
First off, you need to keep the extractor in place for all this, and you need to make sure that the extractor and the extractor recess in the cylinder are completely clean, and that it is sitting as flush with the cylinder as it should be. The extractor will be enlarged by the reamer right along with the rest of the chamber hole. Thus, it behooves you to make double sure the whole area is clean, and that you keep the extractor in its proper position throughout the procedure. To ensure the extractor was secure in the rotatory dimension, I used three fired cases and put them in the chambers I wasn't working on at the moment to secure the extractor from any rotation wiggle while cutting on the chambers.
OK. All that said, we're really doing something very simple, and that is to use the existing chamber diameter to self-center the reamer (at the mouth of the chamber - at the throat, it's the pilot) and then to slowly grind metal in a very controlled and measured manner out of the existing chamber.
I am going to assume you know how to correctly remove the cylinder from the revolver to start with. If you don't, you should find out how before even beginning to attempt this.
To start the procedure, chuck the removed cylinder securely using a non-marring method. I used poly inserts on my vice, coated with a paper towel. Your technique for this may vary, but you need to accomplish a similar thing with securing the cylinder.
Once you have secured the cylinder, you simply give the charging hole and reamer a coat of cutting oil, and place the reamer carefully within the charging hole. Begin to turn the reamer CLOCKWISE ONLY with light to moderate downwards pressure. Every 3 or so complete turns of the reamer, remove it WHILE TURNING CLOCKWISE and clean the flutes, add more oil, repeat until the reamer is almost bottomed out against the cartridge rim recess in the cylinder. Then once more clean the reamer, reinsert and keep a careful close eye on the cutting "lip" of the reamer as you turn the final few turns. Once it begins to touch down on the cartridge recess, stop pressing down, give it a few final light turns to complete the cut, remove and clean. I found it helpful to use a little dykem around the charging holes to show where the reamer was touching down. Once you've given the final few turns with little to no downwards pressure, making sure to avoid cutting on the cartridge recess, you're done. Move on to the next charging hole, clean, lube, and repeat until cylinder done.
Once all chambers are done, fill a small bowl with acetone and give the cylinder a good washing, then give it a good oiling and clean out the chambers. Admire your precision work and easy extraction.
