Accurizing the Ruger Single Action Revolver
Ruger makes a fine single-action revolver. But like most production firearm manufacturers they can't afford to take the time for custom improvements to turn this revolver into an excellent shooter. Additionally the larger-bore Ruger single action revolvers can have other problems detrimental to accuracy. In this article we will identify those problem areas and improve or eliminate them. I used a stainless steel Ruger Blackhawk with a 7 1/2 inch barrel in .45LC to perform my accurizing tasks.
In order to gain maximum accuracy from any revolver, the diameter of the bullets, the cylinder throats, forcing cone, and barrel all must be in harmony. Specifically, the bullet must be one to two thousandths larger than the bore, the bore must be uniform from forcing cone to muzzle, the muzzle must be properly crowned, and the cylinder throats must all be the same diameter as the bullet or .0005" larger. The cylinder throats should not swage the bullets, just guide them. You also need a good trigger pull. I measured these areas on my Blackhawk and this is what I found:
- Cylinder Throats - .450"
- Bore - .451"
- Barrel constriction - .001". This seems to be a common problem with the larger bore Ruger revolvers. The constriction was where the barrel screwed into the frame, and it can be as much as .004".
- Trigger pull 3.5 pounds with a lot of creep. The 3.5 pounds wasn't bad, but the gritty creep definitely needed to be cleaned up.
With these measurements this particular revolver would act as follows:
- Burning gunpowder forces .452" bullet out of case into cylinder throat.
- Cylinder throat swages bullet to .450".
- Bullet jumps cylinder gap into barrel forcing cone. You have to stop and think about this for a minute. In reality the base of the bullet is still in the case when the nose is touching the rifling.
- Barrel constriction ensures bullet stays at .450".
- The .450" bullet is .001" undersize for the .451" bore, so the bullet does not make a tight seal as it travels down the bore. Gas may leak around the bullet causing leading and bullet deformation, who knows how it will exit the muzzle, resulting in a very disappointing group.
- Open up the cylinder throats to .452" - .4525". This must be done before fire-lapping, otherwise most of the lapping process opens up the cylinder throats and doesn't do much work on the barrel. (Yup, I learned this one the hard way!)
- Perform an action job.
- Fire-lap the barrel to remove the constriction and polish and taper the bore.
Reaming Cylinder Throats
I cut a slit in a piece of 3/8 dowel and wrapped a strip of 320 grit wet/dry sandpaper around it so it would fit snugly in the chamber throat. I attached the other end of the dowel to my hand drill, inserted the reamer through the chamber and ran the drill at a medium speed while moving the reamer in and out. I reamed each throat until it measured 0.4525" with my calipers. This not only opened up the throats, but polished them mirror-smooth, which made them much easier to clean. Note in the photo I reamed from the chamber end. This helped me to visually keep the reamer centered in the chamber ensuring I reamed the throats evenly.
NOTE: working on the action requires special tools and jigs and should not be attempted without them. Without these tools surfaces and parts can become rounded to where they will no longer function and/or become dangerous.
I purchased Wolf spring kit RSA-106 from Brownells. It contained a reduced power trigger return spring; 17, 18, and 19 lb. hammer springs (factory is 23 lb.); and a stronger base pin plunger spring. First I completely disassembled the gun and polished all trigger parts and pins. I used 320-grit wet-dry sandpaper on a flat surface to polish the sides of the hammer and trigger. I made sure the trigger was not rubbing against the grip frame. After polishing, cleaning and oiling I reassembled the gun using the spring kit with the 19 lb mainspring to test for reliable function.
I have two stoning fixtures that are designed specifically for shaping and polishing hammer and sear engagement surfaces, both of which are available from Brownells. The Power Custom Series 1 fixture is used for polishing triggers and sears, and the Power Custom Series 2 fixture is used for polishing the engagement surface on hammers. Available separately for the Series 1 fixture are firearm-specific adapters for working on the trigger or sear of a specific firearm. The Series 2 fixture comes with a universal adapter and multiple sizes of pivot pins to mount different hammers from different firearms for polishing. The universal adapter did not have a pin to fit the Ruger hammer so I used the hammer pivot pin from the gun.
With most Ruger SA triggers the trigger sear sits too deeply on the hammer notch. This makes a very safe, but long and creepy trigger pull. Also these surfaces are often just rough ground as they come from the factory so they need some smoothing and polishing.
I installed the hammer in my Power Custom Series 2 stoning fixture using the universal adapter. I used the original hammer pivot pin inserted groove first into one of the holes in the adapter. The pin was held in place by a set screw. I made sure the set screw contacted the groove so as not to raise a burr on the pivot surface of the pin. I marked the front edge of the hammer notch with a blue marker and adjusted the fixture until my stone was flat across the front of the notch. The notch in my hammer measured .022" deep so I took a 220 grit stone and carefully reduced the depth of the notch to .014".
I then rotated the hammer so I could polish the engagement surface of the hammer notch as shown in the photo. I marked the surface with a blue marker and made sure to adjust the fixture so I was polishing this surface perfectly flat. I used my hard Arkansas stone with a beveled edge to final-polish the surface.
Next I installed the trigger in my Power Custom Series 1 stoning fixture using the BH (Blackhawk) adapter. I used a blue marker to mark the surface and adjusted the fixture until I was polishing the surface perfectly flat and square. I used my coarse ceramic stick to polish off all of the grinding/machine tool marks, then final polished with my fine ceramic stick.
With the trigger still installed on the BH adapter, I rotated the adapter until I could cut the rear edge of the sear at a 45 degree angle with a 220 grit narrow stone. After every 10 strokes I cleaned and oiled the surface, then re-assembled the gun and tested the trigger. After about 30 strokes, and with the 19 lb. hammer spring installed, it broke at exactly 2.5 pounds every time with no creep.
Fire-Lapping the Barrel
Fire-lapping involves imbedding different grits of lapping compound into lead bullets and firing them down the barrel at a very moderate velocity. This process accomplishes a number of positive things:
* Smoothes the barrel making it easier to clean
* Removes tight spots
* Slightly tapers the barrel from forcing cone to muzzle
I hoped to eliminate the tight spot under the threads and taper and polish the barrel. I purchased a fire-lapping kit from NECO (available from Brownells) which included 4 grits of lapping compound, 220, 400, 800, and 1200. Their instruction manual said to use lead bullets to fire-lap a revolver barrel, and shoot multiple exact full cylinders of bullets. (This is so each chamber throat in the cylinder gets the same amount of polishing.) They recommended 12 rounds with 220 grit, 18 rounds with 400 grit, and 24 rounds with 800 grit. They did not recommend using the 1200 grit but they stated it would not hurt. So at a minimum this meant I had to prepare 54 loaded rounds. Just to make sure I removed the constriction, I actually loaded 48 rounds of 220 grit.
First I took ninety 250 grain bulk-purchased cast lead bullets and laid them in an aluminum pan. I baked them in my toaster oven at 250 degrees for 30 minutes to remove the lubricant from the lube grooves. Then I took the appropriate number of bullets and impregnated them with the proper grit compound.
I spread a thin layer of compound on the steel plate provided in the NECO kit and rolled 3 bullets at a time between it and another steel plate thereby impregnating the bullets. I wiped off the excess compound from each bullet and separated them by grit in preparation for loading.
The plastic bowl in the photo is marked 400 for putting bullets impregnated with 400 grit lapping compound. I also used bowls marked 220, 800 and 1200.
Finally, I loaded each round with 4 grains of Red Dot which produced a low velocity load.
I started with the 220 grit rounds and fired a cylinder full, then I had to thoroughly clean the barrel and cylinder using a patch soaked with Remington Bore Cleaner and wrapped around a brass bristle brush. Everything got oiled with Hoppes, then I slugged the barrel to gauge the fire-lapping progress. I fired 36 rounds of 220 grit to remove the constriction, cleaning and slugging between every six shots. Then I fired 18 rounds of 400 grit, again cleaning between every six shots, and then 24 rounds of 800 grit for final polish. It is important to clean after every six rounds otherwise you begin to lap the fouling and not the barrel metal. Also, the cases used for fire-lapping should be destroyed. This is because residual compound in the cases can contaminate the bullets and actually cause damage to your newly polished barrel.
This target shows the results. This 25 yard group was shot with cast bullets from Lee mold C452-300-RF sized 0.452" and crimped on the lower crimping groove. It measured 0.588"! This made all my work worthwhile, and it certainly paid off in improved accuracy.
This is what is happening now with my accurized revolver:
- Burning gunpowder forces .452" bullet out of case into cylinder throat.
- .4525" cylinder throat guides bullet into the forcing cone, no swaging occurs.
- Bullet jumps cylinder gap into barrel forcing cone.
- No barrel constriction exists so .452" bullet enters .451" barrel. Because the bullet is .001" oversize all lands and grooves are sealed.
- .451" bullet is in constant contact with the bore because fire-lapping slightly tapered the bore. Bore is sealed, no gas cutting/leading occurs.
- Bullet exit from muzzle is consistent resulting in excellent groups.