By Larsen E. Pettifogger, SASS #32933 Life
In the June and July, 2008, issues of the Chronicle we tuned up a Pietta cap and ball revolver for CAS competition. The next few months, we’ll tune an Uberti open top. In addition to its line of cap and ball revolvers, Uberti also makes reproductions of Colt cartridge conversions and the 1872 Open Top. Photo 1 shows an 1851 Navy on the top, a conversion of an 1860 Army in the middle, and an 1872 on the bottom.
The tuning techniques for all three are essentially the same, so this article will cover all three. From left to right, photo 2 shows the frames for the 51 Navy, the conversion, and the 72.
Photo 3 shows a top view of the three frames.
The back of the frames are all lined up, but the plate on the conversion frame extends much further forward than the recoil shields on the 51 and 72. (This is one difference that we will address when we are doing our tune-up.) Photo 4 shows the cylinders from out 51, the conversion, and the 72.
And, Photo 5 shows the cylinder ratchets (same order).
It is apparent from a side-by-side comparison that the ratchet of the cap and ball cylinder (the 51) is much different that the ratchets on the conversion and the 72.
The cap and ball revolvers use a single-tooth hand. The conversion and 72 use a two-tooth hand, as does the Colt Single Action Army and its clones. (The SAA was the next evolutionary step from the 72.) Photo 6.
This has some impact on tuning since hand pressure on the ratchet helps control cylinder over rotation. The big single-tooth hand stays constantly engaged in the ratchet throughout the cylinder’s entire rotation and acts as a brake on the cylinder. This combined with the large surface area and increased friction of the cylinder arbor (which is much larger in diameter than the cylinder pin on a SAA) and the fact that the arbor is usually covered with grease, which further increases friction, makes it unusual for a Colt cap and ball to over-rotate. On a two-tooth hand there is a slight overlap between when one tooth stops rotating the cylinder and the next tooth takes over. If the handspring is to weak or the bolt timing a little off, a conversion or 72 is
more apt to over-rotate than a cap and ball revolver. Handsprings are the weak link in all open tops and we will permanently fix that problem.
The next noticeable difference is in the wedges used on the three guns. The cap and ball uses a wedge with a spring in it. The tip of the spring, where it sticks through the barrel slot, has a hook on the end. The conversion and 72 use a flat steel wedge with a small recess milled in it. Photo 7.
The most common problem area on Uberti open tops involves these wedges. Most discussions around the campfire go something like – “the proper way to adjust the wedge on a cap and ball is to push it in so that the hook on the end of the spring catches on the opposite side of the barrel. The hook is there to keep the wedge adjusted.” On the conversions and 72’s the conventional advice is normally – “push the wedge in until the milled recess is slightly inside the barrel, then install the wedge screw and push the wedge back out until it seats against the screw. That is how the wedge is adjusted.” The hook on the wedge on a cap and ball and the wedge screw on a conversion and 72 are not intended to be adjustment mechanisms. Their primary function is simply to keep the wedge from falling out and getting lost. The reason open top shooters go through these machinations is to keep the barrel from moving to far to the rear, thereby eliminating the cylinder gap and causing the cylinder to drag or bind-up entirely. As part of our tune-up we are going to fix that problem once and for all as well.
The first things we have to do before starting our tune-up is to fully inspect and function test the gun. Rather than cover the same ground, now is a good time to re-read the inspection portion of the Pietta articles. You did save the June and July 2008, issues of the Chronicle didn’t you? If not, they can be found at
As part of our inspection one of the things we are looking for, and to clean up or polish, are burrs and rough surfaces. One of our tune-up guns had the granddaddy of burrs in it. Photo 8 shows a burr that is roughly one-quarter inch wide and one-half inch long that was curled up inside the frame like a party whistle.
Definitely had to deburr that burr. Another problem that seems to affect Ubertis more than Piettas is that the lever latches are often loose from the factory or fall out after a few matches. Photo 9 shows a latch that was only finger tight in a brand new Uberti 51 Navy.
In this case, the machining on the dovetail and the latch is very precise; there is no gap or up and down movement. It just slides from side-to-side with light finger pressure. Rather than peen, dimple, stake, or any of the other things that could be done to secure the latch, a drop of red loctite in the dovetail is a permanent fix and there is no chance of marring the finish on our gun. Identify and make a list of all the little things you find that will need addressing before the gun is reassembled. Since we have dealt with examples of common fit and finish issues in the
Pietta articles, we won’t spend more time on those issues here. Instead, we will focus on some specific problem areas and how fix them.
In the Pietta articles we also discussed some tools that would be needed to work on our guns. Since most people don’t have milling machines or lathes in their garages, in this article we are going to use tools that many people do own or can borrow from a pard. Photo 10 shows a basic Home Depot type drill press.
Nothing fancy, just a tabletop model. Photo 11 shows a typical drill press vise.
We will need a vise to hold our work while we are drilling some holes needed to tune our guns. Photo 12 shows a couple of center punches.
On the right is a standard old semi-dull center punch. We are going to be center punching some pretty precise locations. So, we are going to use a new (or freshly sharpened) prick punch like the one on the left.
The prick punch has a tip with more taper than a standard punch and will allow us to more precisely locate the punch tip on our work. We are also going to scribe some fairly precise lines. When scribing, remember that if the tip of the scribe is held vertical our lines are not going to be where we want them.
Photo 13 shows a scribe held up vertically against a work piece.
Notice that the tip of the scribe is not scribing along the edge of the work piece, it is scribing to the right several thousands of an inch. Hold the scribe at an angle so it marks a true and correct line on our work. Photo 14.
With these basic tools on hand and procedures in mind, let’s begin our tune-up.
In the Pietta article we spent a lot of time refitting the cylinder bolt. Uberti bolts are generally “sort of fit.” They are not set up ideally, but they do usually work as they come from the factory. Photo 15 shows a typical Uberti open top bolt.
The workers at Uberti typically grind a taper on one side so that the bolt head does “sort of” fit into the cylinder notches. Fitting the bolt so both sides of the bolt are parallel with each other would be better, but Uberti’s method of fitting bolts does make the bolt serviceable. Photo 16 shows a bolt out of a brand new Uberti that was ground on the wrong side.
If this happens in one of your guns, it’s time to order a new bolt as this one is a problem waiting to happen. Here’s why. Photo 17 shows a head-on view of the bolt depicted in Photo 15.
The side of the bolt head at “A” is vertical and higher than side “B”. The top of side “B” is also tapered slightly towards side “A.” Side “A” is taller because the cylinder notches are machined off-center from the centerline of the chambers and the chamber walls are, therefore, thicker where “A” engages the cylinder notch. Photo 18 shows the BOTTOM of the cylinder.
The cylinder rotates clockwise, but because we are looking up from underneath it is rotating in the direction of the green arrow. Notice that the cylinder notch is to the right of the nipple. The nipple is on the centerline of the chamber; this shows how much the cylinder notch is offset.
As our cylinder rotates, the bolt drops into the leade at “B” and slides into the notch. Side “A” of the bolt in Photo 17 slams into the cylinder notch wall at “A” in Photo 18. That’s why side A needs to be square with the cylinder notch walls and why its extra height also helps.
The extra height gives the bolt head on the thrust side of the cylinder’s rotation more engagement material to stop cylinder rotation and firmly lock up the cylinder. If side A is tapered or worn (or the cylinder notches are worn) the bolt can bounce out and cause cylinder over-rotation. Photo 19 shows the bolt fully engaged in the cylinder notch.
If your bolt fits the notches, we are ready to proceed. If it doesn’t, or the taper is on the wrong side, follow the instructions in the Pietta article and refit a new bolt. Just remember any material that needs to be removed should always be removed from side “B” of the bolt. In part 2 we will alter the hand and frame to use a coil spring and plunger.
We are going to do some modifications to our frame that will allow the use of a coil hand spring and plunger – thereby eliminating hand spring breakage and help smooth up the action – and modify the arbor to eliminate wedge problems and cylinder binding.
In order to do this, we need to drill some precisely located holes in our frame. Whenever a hole has to be drilled or a part modified, the first thing to do is look for any reference point on the work piece that will facilitate getting the job done as easily as possible. On our frame, if it is lying down in its normal shooting position all the machined surfaces are angled.
It would be very hard to locate or drill a hole in these angled surfaces. However, if we stand the frame on end everything changes. First, we can see that the arbor is parallel to the top of the cylinder window. Photo 21 at “X”.
Second, we can see that the arbor and the back strap area of the frame are set at 90 degrees to each other. Photo 21 at “Y”. We can use these surfaces to accurately guide the location of our holes. Our first task will be to drill the hole for our new hand plunger and coil spring.
The first thing we need to determine is where the hole has to be located. We start by measuring the thickness of the hand.
In this case the hand in our gun is .140” thick. Ideally, the plunger should ride in the center of the hand, so half the thickness of the hand would be .070”. However, many hands, including our Uberti hand, have a boss at the bottom of the hand to space it out from the hammer.
To find the thickness of this boss simply measure across the bottom of the hand, including the boss, and then subtract the dimension we got in Photo 22 from the total hand thickness. Photo 23.
In this case the bottom of the hand, including the boss, is .170”. Thus, in order to get the plunger to ride in the center of the hand we take half the thickness of the hand and add the TOTAL thickness of the boss; in other words, .070” + .030” which gives us a total of .100”.
In order to locate this dimension on our frame set your dial calipers to .100”. On the opposite end of the caliper there will be a tab sticking out .100”.
Take a black magic marker and blacken the frame above the left grip frame screw hole.
Then set your calipers up against the frame and scribe a line along the end of the tab.
Remember to angle your scribe like that shown in Photo 14 in order to get an accurately scribed line. The distance in from the side of the hammer channel is fairly critical. However, the location of the hole between the top of the frame and the screw hole is less critical. You just need to make sure the drilled hole will not extend above the top of the frame or into the screw
hole. Take your punch and tilt it sideways so you can see that the point is on your scribed line and about equal distance between the top of the frame and the grip screw hole. Photo 27.
Tilt the punch up and when you are sure the tip has not moved and is still on your scribed line tap the punch with a hammer and center punch the location of the plunger hole. Photo 28.
The best way to get a firm hit is to put the arbor in a vise (make sure you pad the jaws) with the arbor facing down and the recoil shield resting on top of the vise jaws.
Now that our holes location has been established on the back of the frame, we need to set it up so the hole can be drilled.
On the drill press vise in Photo 11, the jaws are relatively deep and the sides of the jaws are perpendicular to the top of the vise.
One way to set the frame up so that it is square is to put the arbor in the vise jaws and then firmly press the frame up to the sides of the jaws. Photo 29.
Since the top of the cylinder widow is parallel to the arbor and the arbor is set at 90 degrees to the bottom of the frame (Photo 21) this will give us the proper 90-degree angle to drill our hole. Depending on how your drill press vise is configured, you may have to try different ways of securing the frame in the vise.
For example, the jaws in the drill press vise shown in Photo 30 are too short to allow using the cylinder window to square the arbor. So, we can turn the frame around and use the arbor to square the frame. In Photo 30 the frame is now held in the vise.
The sides of the vise jaws are square, but they don’t extend down far enough and the arbor hits the base of the vise below the arbor and will tilt the frame.
Again, as long as we keep everything parallel we can space the arbor out from the frame and still keep the base of the frame square.
In Photo 30, a piece of flat steel stock is placed between the arbor and vise jaws and then everything is pressed against the vise jaws. This will maintain the relationship between the arbor and cylinder window.
(Before tightening the vise jaws on the frame make sure to insert some shim stock to keep from marring the frame.)
You simply need to look at your particular vise and determine how to best secure the frame to get the base of the frame perpendicular to your drill bit.
Once your frame is properly secured, put a number 35 drill in your drill press and move the vise under the drill. (Number drills can be obtained from most hardware stores, hobby shops or Brownell’s.)
With the drill press NOT running, slowly lower the drill bit and watch the tip of the drill VERY carefully. As it hits the center punch dimple it will deflect if it is not centered exactly. Keep moving the vise (VERY small movements) until when you lower the drill it hits the center punch dimple and does not deflect.
At that point it should be centered fairly well and you can turn on the drill press and drill your hole. Photo 31.
Keep drilling until the bit goes through the frame into the hand channel. Once the hole is drilled it should look like the one in Photo 32.
Take the frame out of the vise and insert a standard Ruger plunger and spring. Photo 33.
(Brownell’s part numbers 780-012-104 or 780-012-105. Midway also carries Ruger parts although it will have a different part number.)
This plunger and spring is found in virtually all Ruger single actions. If it drags in the frame at all, take the number 35 drill between your fingers and spin it back and forth while moving it in and out of the hole. Photo 34.
This should remove any burrs that might have been left in the hole.
Uberti hands are usually smooth on their backside so little polishing is needed. On the percussion hand (Photo 6, left hand) simply pull the old handspring down and it will break off.
(See the Pietta article for more detailed instructions and photos.)
Put the hand on the hammer and install it in the frame and then put in the plunger and spring. Put on the back strap (to compress the spring) and cycle the hammer. Without the cylinder, sometimes the hand won’t move smoothly since it is going further forward than it would with the cylinder in place and will jam or drag in the hand slot.
Simply take a screwdriver tip and push the hand back a little. At this point, all we are checking is to see if the plunger is to short. These guns vary a bit from gun to gun and sometimes the plunger will be to short.
If the plunger drops through the frame hole into the hand channel don’t worry there’s a simple fix. Simply cut a piece off the end of the number 35 drill you used to drill the plunger hole and use that as a new plunger. Photo 35.
The conversions and 72’s hands are two-tooth. Photo 6, right hand. (The hand in the photo is out of a conversion.) The 72 hands generally fit into the gun about the same as the percussion
models and you can use the same standard Ruger plunger and spring set-up. The conversions, however, take a little more work.
As shown in Photo 3, the conversion plate extends forward from the recoil shield. On the stock hand, the handspring sticks back from the hand to take up this extra space. Photo 6, right hand. Because the hand sits further forward in the frame, the Ruger plunger and spring and to short. So short, in fact, that even making a longer plunger out of the end of our number 35 drill won’t work. Again, a little work will solve the problem. Break off the hand spring and work the back of the hand on a stone until you have two small flat spots stoned on the back of the hand. Photo 36.
Then go to your local friendly hardware store and buy a piece of 1/8th inch square keyway stock. They are generally an inch long and this will work about perfect. If your keyway is bright and shiny it is probably plated with a coating to make sure it doesn’t rust. Put the keyway on a stone and work it back and forth a few times to remove the coating. Photo 37.
While it’s on the stone, mark the top of the keyway with a little black mark from your magic marker and place the keyway on top of the hand. Photo 38.
Once the keyway has been stoned, the stoned surface will also be bright and hard to tell from the coated surfaces. The black mark will help identify which side goes down in case you drop the keyway while working with it. Next solder the keyway to the back of the hand. (Put the end of the keyway right above where the old hand spring was broken off.) Photo 39.
Cut the keyway off just below the top of the hand. A Dremel with a cutoff wheel works well for this. And, round off the bottom of the keyway. See photo 39 again.
Put the hand on the hammer and install it in your frame. One thing that makes installing even the original hand and spring difficult at times is that the hand channel on most Uberti’s is oval shaped at the bottom and the sharp edges of the hand or the flat leaf spring hang up going over this oval portion of the hand channel. You can see the oval shape in Photo 40.
Carefully work your new hand up into the channel looking at it with the little flashlight shown in the Pietta article. Sometimes a little material has to be removed from the outside corners of the keyway to get it to slide past the oval part of the frame. Once the hand is inside the hand channel, and the hammer screw is installed, gently cock the hammer and with your little flashback look for any interference between the bottom of the hand and the hand channel. (Especially in the oval area of the hand channel.) Stone a little material at a time at the bottom of the piece of keyway we soldered to the hand until the hammer comes back almost to the full cock position. Install the back strap and keep stoning the keyway until the hammer goes to the full cock position. Photo 41.
When you are finished, the hand should look something like the hand shown in Photo 42.
We are now halfway through our Uberti modifications. In part 3 we will begin fixing the wedge/arbor fit.
Parts 1 and 2 of this series dealt with more or less standard action tuning procedures and between them and the information in the Pietta articles, the actions on your guns should be a little smoother. However, a smooth action is useless if the cylinder binds and the gun is difficult or impossible to cock. This difficulty comes primarily from the cylinder gap closing because the wedge is going too far into the barrel, or powder fouling building up on the face of the cylinder (especially with black powder). The reason this occurs with Ubertis is because almost every Uberti open top has a poorly fitted arbor. In almost every case, the arbor is too short. Since the arbor is too short, as the wedge is pushed into the barrel it tilts the barrel backwards and it binds on the cylinder or reduces the cylinder gap to the point that powder fouling makes the cylinder hard to turn.
To test for this condition, remove the cylinder and make sure all gunk and dirt is out of the arbor hole in the barrel. Put the barrel on the arbor at a 90-degree angle to the frame and make sure it is fully seated on the arbor. Photo 43.
(Make sure the arbor is in the arbor hole and not the bore!) Now twist the barrel down until it comes to rest on the barrel alignment pins or the frame. Photo 44.
If the arbor is properly fitted, the barrel will either mate perfectly with the frame or be only a FEW thousands of an inch behind the frame. Perfect alignment is shown in Photo 44. On virtually every Uberti, the barrel will wind up a good distance behind the front of the frame. Photo 45.
As long as this misalignment between the barrel and frame exists, the cylinder gap will never remain perfectly set. Once the arbor is properly fitted, it will remain that way for virtually a lifetime. Photo 46 shows an original Colt.
It is over 140 years old; there is a lot of wear on the arbor and in the arbor hole in the barrel, yet it still mates perfectly with the frame. So, how do we fix this problem? More importantly, is there a way the home gun tinker can repair the arbor?
One way to repair the arbor is to remove it and either try and find one that is longer or to weld up the existing arbor and machine it to fit. This is not practical for the home smith. There are a few other things that can be done. A precisely located hole can be drilled in the end of the arbor and a spacer installed. Photo 47.
Another method is to drill a hole in the arbor recess in the barrel and install a setscrew. Photo 48.
The barrel/frame fit can then be adjusted by simply turning the setscrew. Photo 49.
A setscrew can also be fitted to the end of the arbor. Photo 50.
All of these methods present some potential problems. For example, the hole for the setscrew or spacer has to be centered well and the hole tapped perfectly straight or the setscrew or spacer
won’t seat squarely on the top of the arbor or in the center of the arbor hole. Also, the bottom of the arbor hole on Ubertis is typically not flat. It is concave in the center. That is why the setscrew or spacer must be well centered. If it is not, the screw will hit the concave area of the arbor hole and give poor contact with the barrel. Sometimes the arbors are hardened fairly deeply and are difficult to tap. Besides these mechanical problems, there is also a practical problem on many Ubertis.
The cutout in the barrel under the loading lever is sloped. On many of the open tops, cap and ball and cartridge, the bottom portion of the arbor hole is paper-thin or has been perforated during the machining process. For those guns with thin metal in the arbor hole or for those that are perforated, this makes installing a setscrew an unsatisfactory fix. (It is also somewhat difficult to measure exactly how thick the metal in the arbor hole is because of the sloping surfaces.) Photo 51 shows a “C” series second generation Colt 51 Navy barrel looking from the cylinder end.
The center hole is the arbor hole and it can be seen that the lower half of the hole is perforated. Photo 52 shows the arbor hole looking down into the loading lever cutout.
Again, the perforation is apparent. So, does this mean if the metal in the arbor hole is thin or perforated that we can’t fix the arbor fit? No! The cutout in the barrel is sloped. So, even though the bottom half of the hole may be paper thin or perforated, the upper half is quite thick and will serve as a solid bulkhead for our arbor to bear against. It turns out the solution to our problem is something a lot of us already have lying around in our gunrooms. A Dillon #3 locator button! Photo 53.
(Dillon part number 14060.) That’s right, one of those little brass buttons that locates the casings in all of the Dillon loading machines. The button is cheap, big enough to make solid contact with the bottom of the arbor hole, yet small enough that if we make a small centering error it will still fit in the arbor hole, and, being brass, it is easy to machine.
The first thing we need to do is look at the end of the arbor. It’s either flat, or it isn’t flat! The arbor in Photo 54 has a small nub left in the center from when the arbor was turned during manufacture.
That little nub is right where our locator hole has to be drilled, so it has to be removed so we can get an accurate center punch location. Take a stone and stone the nub down until the stone makes uniform contact with the tip of the arbor. Photo 55.
On our arbor, the end of the arbor is shaped like a donut. The center is flat as are the edges of the arbor, but the area in between is slightly lower. Photo 56.
As long as the nub is flat and there is even contact from the stone around it, we don’t need to stone any further. At this point, we can use the bright spot left by the nub to center our punch. Remember to use a new, sharp, prick punch so you can see where the punch tip is contacting your work. Angle the punch, put the tip in the center of the spot left by the nub, photo 57,
straighten the punch and when you are certain it is centered, give it a tap with a hammer. Photo 58.
If there is no nub, or if the end of the arbor is all bright and shiny after you have stoned off the nub, or you don’t trust your eyeball centering on the nub, then we have a little more work to do to make sure our center punch is accurately located. Take a black magic marker or sharpie and blacken the end of the arbor. Photo 59.
Now we need to scribe lines in the black surface to locate the center of the arbor. A machinist’s centering square would be the simplest thing to use. Photo 60.
It is designed so that when it is placed on a round object the leg of the square runs through the center of the round object. Photo 61.
Not everyone has one of these things and they usually can’t be purchased at local hardware or tool stores. An alternative is a combination square that can be purchased at many local stores. Photo 62.
This is a cheap one that was picked up from Harbor Freight for $7.00. Remove everything but the center finder and you wind up with a giant, but serviceable, version of the little machinist’s square. Photo 63.
Put the arbor in a vise with the tip sticking up far enough so that your square can fit down tightly against the end of the arbor. Photo 64.
(Make sure to use some shims or padding so you don’t damage the sides of the arbor.) Scribe a line down the center of the arbor. Remember to tilt your scribe so that it makes an accurate line. Photos 13, 14, and 64. Turn the square 90 degrees and make a second line. “X” now marks the spot. Photo 65.
Tilt your punch to accurately locate it at the center of the X, photo 66,
tip it up, photo 67,
and when you are sure it is centered give it a tap with a hammer. You should now have a nice, centered, punch mark. Photo 68.
In the next installment you will get to do some home machining and use that Dremel you have been dying to use!
When we finished part 3, we had marked and punched the center of our Uberti open top arbor. We are now ready to install and fit the Dillon #3 locator button and make our open tops ready for competition. This modification is the single most important thing that can be done to an open top for long-term longevity. WAY back in Part 1, Photo 11, a typical drill press vise was shown. Also in Part 1, Photo 21, the relationship between various angles on our open top frames was shown. To install the locator button in the arbor we need to be concerned with the “Y” dimensions in Photo 21. On most drill press vises the bottom of the vise is perpendicular to the jaws of the vise, Photo 69,
and will maintain our “Y” dimension. On this particular drill press vise the frame was simply inserted and the bottom of the frame firmly pressed down on the bottom of the vise while the jaws were being slowing tightened. Photo 70.
Remember, we are not out to crush the frame, simply to hold it tight enough for drilling.
Put a number 28 drill into your drill press chuck and put the vise under the drill. With the drill press NOT running, slowly lower the drill bit until it hits the center punch mark and look for any deflection of the drill bit. Move the vise until when the bit hits the center punch mark it is dead center and there is no deflection of the tip of the bit. Photo 71.
Drill the tip of the arbor right through into the wedge slot. Where the shank of the locator button joints the head of the button there is a small radius. This radius could prevent the locator button from seating squarely on the top of the arbor. So, without moving the vise, change the drill bit to a number 1 bit and just lightly kiss the top of the hole you just drilled. Photo 72.
This will make a chamfer for the button to fit into. Photo 73.
Take your locator button and drop it into the hole. Photo 74.
If all went well it should drop right in and sit flush on top of the arbor. Photo 75.
Yes, the shank of the locator button is sticking into the wedge slot. Photo 76.
At this point, don‟t worry about it or try to shorten the shank. We need that extra length for the next operation.
Now comes the part where you get to do some machining and actually use your Dremel and not ruin your gun! Install the barrel on the arbor at a 90-degree angle and rotate it down to the frame. The barrel is now in FRONT of the frame, Photo 77,
instead of behind it, Photo 45. Take your electric drill, (yeah, I know it‟s actually a „drill motor‟, but this article is for the average guy and average guys just call them drills) put it into a vise pointing up. GENTLY tighten the vise just enough so that the drill won‟t fall out of the vise. If you tighten it to much you‟ll get to see if Home Depot will really honor that money back guarantee! (If you don‟t have a bench vise but have an extremely strong and patient neighbor, he may be able to hold the drill for the next operation.) Now go get your Dremel and put a sanding drum in it. Put the locator button in the drill chuck and turn on the drill. Now take your Dremel, turn it on, and gently start machining the head of the locator button to make it thinner. Photo 78.
The two rotating devices will ensure that the button is machined evenly. After you have thinned the button a bit, remove it and check to see how close the barrel is getting to the frame. In Photo 79, we are about halfway done.
On some guns, depending on how far off the arbor was when it was originally fit; the head of the button is going to get fairly thin and might bend if you press to hard with the Dremel. To help prevent this, if the head is starting to get very thin, put a steel washer under the button head to help support it. Photo 80.
Keep grinding and checking the fit until when you rotate the barrel down it mates flush with the frame. Photo 81.
Next, put in the cylinder and mount the barrel to do a preliminary check for cylinder gap, on the cap and ball guns, or cylinder gap and end shake, for the 72‟s and conversions (which have cylinder bushings). Part 1, Photo 4. On the 72 in Photo 82, the end shake and cylinder gap appeared about perfect.
You can also see the shank of the locator button sticking into the wedge slot in Photo 82. This now has to be shortened so we can move on to the final fitting. Put a cut off wheel in your Dremel and cut off part of the shank. Photo 83.
Try it in the arbor and then grind a little material off at a time, Photo 84,
until when the button is seated in the arbor it no longer protrudes into the wedge slot. Photo 85.
Now comes the moment of truth. Put in the wedge and, hopefully, everything will be properly aligned. In Photo 86 the wedge goes in just a little past the bottom of the wedge slot and our retaining screw will fit in with no problem.
This 72‟s arbor, barrel, and cylinder all wound up fitting perfect so this particular gun is finished.
Guns have tolerances, however, and sometimes the wedge might not go into the wedge slot far enough, or the cylinder gap is too big, or there is too much end shake, etc. Sometimes the button head may have to be thinned to allow the barrel sit just slightly behind the frame. This will allow the wedge to tilt the barrel back just a little to adjust the cylinder gap and end shake. On the conversions and 72s, if the cylinder binds or drags and there is a gap between the cylinder bushing and the barrel, then some material may have to be removed from the back of the forcing cone area of the barrel. In other words, in Photo 82 if the barrel is contacting the cylinder at “A” and there is a gap at “B” it might be necessary to remove a little material from the back of the barrel at “A.” The object of the button adjustment is to ensure the cylinder gap is established and maintained by the cylinder bushing contacting the barrel around the arbor hole so that once the wedge is inserted, the cylinder gap can no longer change. We don‟t want the cylinder face dragging on the back of the barrel.
The cap and ball guns are different because they have no cylinder bushing. With the hammer at half cock pull the cylinder to the rear. You should have a gap between the barrel and the cylinder. Photo 87.
When the gun is brought to full cock, the hand will push the cylinder forward until it contacts the back of the barrel. Photo 88.
If the gap is to large, over .010” or so, thin the button until when the wedge is inserted the gap is reduced. If there is no gap or it is very small (below .004) then some material may have to be removed from the back of the barrel. The object of the button adjustment on the cap and ball guns is to have a gap at halfcock that will not change when the wedge is inserted. With a properly set gap, as fouling builds on the cylinder face, the cylinder will be pushed slightly to the rear by the fouling buildup but still have enough gap to turn freely.
Remember on all of these adjustments DON‟T remove any material from the gun parts until you have exhausted all attempts to adjust the barrel, arbor, cylinder fit by making adjustments to the button. What is nice about the button adjustment is that if you make a mistake, you are only out a dollar and can simply make another one. Once everything is set and gapped properly you can
put the button back in the drill and lightly polish the dull surface left by the Dremel. Photo 89.
This is entirely optional and is only cosmetic. But, since you will want to show all your friends your work you do want it to look nice, right? After final fitting and polishing put some loctite on the button shank and seat it in the arbor hole. You don‟t want it falling out and don‟t want to mix it up with one from another gun, as each button will be custom fit to each gun to make up for individual arbor variances.
One side benefit from the 2nd Gen Colt‟s perforated arbor hole shown in Photos 51 and 52 is that the results of our work can be seen. In Photos 90 and 91 the brass button can be clearly seen bumped up against the end of the arbor hole.
Now that this gap has been filled, your wedge can do its job and properly seat the barrel to the frame. Your cylinder gap won‟t vary and you will have years of trouble free shooting. If
anything ever changes (you change barrels or cylinders, etc), heat the arbor, pull out the button, and simply start over.