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It's almost a given that many mass-produced guns will have rough chambers, even to the point of sticky extraction with normal factory loads, or badly-scratched brass. Most of the Ruger Blackhawks I have owned exhibited rough chambers, and I've seen one that had burrs bad enough that fired cases were difficult to extract. Fortunately, the cure is simple and easily attended to by anyone with some basic tools.
The following picture shows the basic tools & supplies required: A short length of steel rod, split for about an inch; some strips of 'wet-or-dry' sandpaper, and a caliper. Even the caliper isn't strictly required, but speeds the process somewhat. Not shown is a can of WD-40 or some other similar light oil.
I'd recommend starting with 400 grit. That's normally enought to clean up the burrs and rough spots, but not
so aggresive that there is any danger of recutting the chamber oversized. Normally, 400 grit will just smooth off the burrs and high spots, not even completely removing the original reamer marks & bluing. Start by cutting or tearing the sandpaper into strips about an inch wide. The length will be determined by the amount of paper needed to wrap around the rod until just below chamber diameter. In this example, the rod is 3/8" (0.375") and it take about 10 inches of paper to bring it up to chamber diameter, normally about 0.483" or so for Ruger .45 Colt cylinders. The caliper can help find the exact length of paper needed to bring the assembly up to a snug fit into the chamber.
Start the paper in the slot, then wrap grit-side-out in the direction that you will turn it. It isn't necessary for the assembly to be a tight fit in the chamber; too tight a fit and the paper will just tear and you'll have to start over. Just wrap until there is some resistance to starting it into the chamber. I prefer to start the assembly in the chamber, then chuck the rod in the drill press.
The chamber should receive a spritz of WD-40 or some other light oil before starting. 'Wet-or-dry'sandpaper will cut much smoother when wet. Don't drown the paper or it will just tear. Chuck in the drill press (possible to do this with a hand drill, but much handier to do with a drill press!), and just hold the cylinder in your hand. If you clamp the cylinder in a vise or other fixture, there is a risk of cutting the chamber off-center. Set the speed of the drill to one of the lower settings, the lowest on my drill press is about 600 RPM.
As long as the rod is straight, and the chuck runs true, it wll center itself up in the hole. The exposed part of the sandpaper will quickly wear down, which limits the amount of material removed. As you can see from the next picture, only a little over an inch of the paper has made any contact with the chamber walls. Run time is notof much consequence, as it only takes a few seconds for the grit to wear down on the paper. Just try to keep it consistent; 10 or 15 seconds is fine. Move the cylinder up and down a little as the drill turns so each part of the chamber gets some exposure to the grit. The cylinder will warm slightly from friction, but not so much that gloves are necessary to hold it.
That's it! Repeat for each chamber. You can re-wrap the strip of paper and use the other (fresh) end on the next chamber, but after that, the rest of the paper can't be used (unless you have another, smaller-diameter cylinder that can use the remaining 'good' sandpaper on the strip). Clean the oil/grit/sludge off of the cylinder, re-install, and enjoy cases that fall out of the chambers under their own weight!
This process can also be used to open up slightly-undersized throats, but is much slower than using a reamer.
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