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• Cylinder Throats - 0.450”
• Bore - 0.451”
• Barrel constriction - 0.001”:  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 0.004”!
• Trigger pull – 3.5 pounds with a lot of creep

With these measurements this particular revolver would act as follows:

1. Burning gunpowder forces 0.452”bullet out of case into cylinder throat.
2. Cylinder throat swags bullet to 0.450”
3. Bullet moves across the cylinder gap into the barrel forcing cone.  Actually the bullet is still in the cylinder when it enters the forcing cone.
4. Barrel constriction ensures bullet stays at 0.450”
5. 0.450” bullet is 0.001” undersize for the 0.451” bore, bullet does not make a tight seal as it travels down the bore, gas leaks around the bullet causing leading, who knows how it will exit the muzzle, resulting in a very disappointing group.

So, to accurize this revolver I want to perform the following tasks:

1. Open up the cylinder throats to 0.452 - 0.4525.  This must be done before fire lapping, otherwise most of the lapping opens up the cylinder throats and doesn’t do much work on the barrel.
2. Perform an action job.
3. 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 paper around it so it would fit snuggly in the chamber throat and attached the other end of the dowel to my drill.  I applied a few drops of oil to the paper, 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”.  This not only opened up the throats, but polished them mirror smooth which made them much easier to clean.  Note in the above figure I reamed from the chamber end.  This helped me to visually keep the reamer centered in the chamber ensuring I reamed the throats square. 

Action Job 
First I installed a spring kit.  I purchased kit RSA-106 from Brownells product SKU# 080-665-106 which 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 made sure the trigger was not rubbing against the grip frame.  (I had this happen on one revolver I worked on!)  I also polished inside the frames where moving parts made contact using 400-grit polishing stones and oil.  After polishing, cleaning and oiling all internal parts I reassembled the gun using the spring kit with the 19lb. mainspring to test for reliable function.  I resized and primed 6 cases with CCI primers.  CCI primers are noted for being harder than other primers.  I loaded the primed, empty cases into the cylinder and tested to make sure each primer fired reliably.

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 I purchased from Brownells product SKU# 713-270-014 using the universal adapter Brownells product SKU# 713-271-000.  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 0.022” so I took a 220 grit stone and carefully reduced the depth of the notch to 0.014”.

I then rotated the hammer so I could polish the engagement surface of the hammer notch as shown in Figure 2 above.  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 Brownells product SKU # 713-070-008.  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 ceramic stones Brownells product SKU# 080-721-621 to polish the sear.  I used the coarse ceramic stone to polish off all of the grinding/ machine tool marks, then final polished with the fine ceramic stone.  Ceramic stones use water as the cutting agent, not oil.   

I applied a bit of Action Lube Plus available from Brownells product SKU# 083-050-002 to the hammer and sear mating surfaces to ensure smooth function and to prevent corrosion.  I re-assembled the gun and tested the trigger.  With the 19 lb. hammer and lighter trigger return springs 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 which makes it easier to clean
• Removes tight spots
• Slightly tapers the barrel from forcing cone to muzzle

I really wanted to eliminate the tight spot under the threads; tapering and polishing the barrel were added benefits.  I purchased a NECO fire-lapping kit 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 couldn’t 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 cast lead bullets that I bulk purchased already cast and lubed and laid them in an aluminum pan.  I baked them in my toaster oven at 250° for 30 minutes to remove the wax lubricant from the lube groove.  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 imbedding the compound into the bullets.  I wiped off the excess compound from each bullet and separated them by grit in preparation for loading.  I loaded each round with 2-grains of Red Dot which produced a low velocity load. 

Now it’s off to the range I go.  I started with the 220-grit rounds and fired a cylinder full, then I had to thoroughly clean the barrel and cylinder using a .38 caliber patch with Remington Bore Cleaner wrapped around a .44 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, after using the cases for fire-lapping they should be destroyed.  If you reload these cases residual lapping compound can contaminate the bullet which will damage your barrel.  However, if you plan to accurize more then one gun of the same caliber, you can re-use the cases, but you must keep them separated by grit. 

Cleaning Up the Muzzle 

Nicks and imperfections on the muzzle can be detrimental to accuracy.  To ensure the muzzle is completely free of any nicks or imperfections I lapped it using a brass muzzle lap available from Brownells product SKU# 080-764-000.  I chucked the lap in my hand drill and put some 400-grit lapping compound on the end of the lap.  With the drill running at 500-700 RPM I pressed the round end of the lap against the muzzle at the angle shown in the above photo and rotated the drill through 360-degrees keeping the lap at the same angle.  I did this for about 30-seconds making sure I kept rotating my drill in a circular motion.  I washed off the lapping compound with brake parts cleaner.

The figure above shows the results.  This 25 yard group was done with bullets sized 0.452”.  It measured 0.774”!  This made all my work worthwhile, and it certainly paid off in improved accuracy.  This is what is happening now with my accurized revolver:

1. Burning gunpowder forces 0.452”bullet out of case into cylinder throat. 
2. 0.4525” cylinder throat guides bullet into the forcing cone, no swaging occurs. 
3. Bullet moves across the cylinder gap into the barrel forcing cone. 
4. No barrel constriction exists so 0.452” bullet enters 0.451” barrel.  Because the bullet is 0.001” oversize all lands and grooves are sealed. 
5. 0.451” bullet is in constant contact with the bore because fire-lapping slightly tapered the bore.  Bore is sealed, no gas cutting/leading occurs. 
6. Bullet exit from muzzle is consistent resulting in excellent groups. 

These are procedures that any hobby gunsmith can perform and work well for any revolver, whether single or double action. 

Addendum

Although I was able to open up the cylinder throats by reaming them with wet/dry sand paper, the proper tool is a cylinder throat reamer available from Brownells product SKU# 513-000-002.  This reamer opens up the throats to 0.4525”.

First I installed the T-handle from my .38-.45 Basic Chamfering Kit, Brownells product SKU# 080-479-451, to the end of the reamer.  I chucked the cylinder in a padded vice, lubricated the reamer with cutting oil, and inserted it from the chamber-end of the cylinder.  I turned the reamer clockwise as viewed from the handle end until the reamer protruded from the end of the chamber.  I never want to turn the reamer counter-clockwise as this can break the teeth.  I cleaned off all of the metal chips before removing the reamer according to the included instructions.  Now all the throats consistently measured 0.452”.

Finally I wanted to polish the throats to remove any burrs or reaming marks.  Brownells sells a cylinder hone specifically designed to polish chambers in revolver cylinders called a Flex-Hone, refer to my article Polishing RevolverChambers.  This is the correct tool for polishing chambers and consists of small balls of polishing grit on the ends of a spiral wire brush.  The Flex-Hone comes in two different grits, medium product SKU# 080-608-145 and fine product SKU# 080-608-246.  The medium-grit hone is used to polish-out the tooling marks, and the fine-grit hone is used to final-polish the chamber.  Brownells states that you should only use the Flex-Hone Oil product SKU# 080-609-008 as the cutting/lubricating agent, and that you should not spin the hone any faster than 750 RPM.  This is well within the slow speed of my cordless drill. 

I used the fine Flex-Hone to polish out the tooling marks.  I put a few drops of Flex-Hone oil in the chamber, chucked the hone into my cordless drill and ran the Flex-Hone in and out of the chamber at slow speed for about 30-seconds.  Now each chamber throat is consistent and polished.