I was working a shift at the gun club recently, and one of my friends was eager to show me his new revolver. As he was talking me through the details of the new gun, I noticed that the rear sight was pushed far over to one side, and my friend explained that the correction had been necessary to get the gun to shoot straight.
Being a RevolverGuy, I have to admit I was a little suspicious. My friend is a very good marksman, but his preferences in handguns trend towards single action and striker-fired autos, and this wouldn’t have been the first time that I saw a shooter who was accustomed to short-travel, autopistol triggers struggle with the long, double action trigger on a revolver. I’ve seen lots of pistol shooters who wound up pushing or pulling their revolver off target as they wrestled with the long trigger stroke on the gun, so that’s the first place my mind went when I saw the displaced rear sight.
My friend asked me to try the gun to see if it shot differently in my hands. “It would be nice to know if the problem is the gun, or if it’s me,” he said.
I dutifully loaded the revolver with six rounds and proceeded to give it a go. When I lowered the revolver to examine my target, I expected to see a nice, but displaced, group as a result of the radical sight correction on the gun. Instead, I was greeted by a nice group in the center of the Bull.
Normally, a group like this would be a good thing to see, but I wasn’t relieved by this one. Instead, I was now convinced there was a problem with the gun. With the rear sight pushed all the way over to one side, this gun should have grouped wide, but the fact it didn’t indicated there was something wrong.
It only took a second to confirm my suspicion. A quick examination of the unloaded gun revealed the problem, and I had the sad responsibility of telling my friend that his brand new gun had a flaw—it’s barrel wasn’t properly installed, and it had a “clocking” error.
When a barrel is installed on a revolver frame, the timing of the threads on the barrel extension and the frame itself has to be just right for everything to line up in the right place. A small difference in the thread pattern, or a frame or barrel shoulder that’s not properly dimensioned, can result in a barrel whose shoulder bottoms out against the frame too early or too late. This results in a front sight that’s angled off to one side, instead of being perfectly centered and perpendicular to the topstrap of the frame, at top dead center (TDC).
If you’ve ever had to do any kind of home plumbing repairs, you’ve probably encountered something like this. In example, I recently had to replace a hose spigot in the backyard, and when I got the new one threaded onto the pipe, it was no longer oriented straight up and down like the old one was, but was instead about 10 degrees off true vertical. Grrrr.
There may be a different term that’s preferred for this situation (maybe “timing” or “indexing”), but we’ll call it a “clocking error” here, because the part isn’t oriented at 12 O’ Clock, like we want it to be, but instead is pointing at some other clock position on either side of center.
The problem, from the shooter’s perspective, is that a clocking error leaves the front sight angled to one side or the other, and this has a negative influence on accuracy.
If the front sight is angled too far to the right (from the shooter’s perspective), for example, the shooter will likely see it crowding the right side of the rear notch when he aims the gun, and will “correct” the problem by angling the barrel towards the left, to “center” the front sight in the rear notch. This results in the bullet striking to the left of where the shooter wanted it to go. RevolverGuy readers may recall that Justin encountered this very issue on a 4” Smith & Wesson Model 610 that he evaluated here in these pages.
The reverse happens if the front sight is angled too far to the left. The shooter will move the barrel to the right, to “center” the front sight in the rear notch, and the rounds will impact to the right of center.
Since most revolvers are threaded so that a barrel is turned clockwise (when viewed from the muzzle end) to screw it into the frame, a barrel shoulder that bottoms out on the frame too early will leave the front sight angled towards the right, from the shooter’s perspective (towards 11 O’ Clock, from the muzzle end). This results in bullets impacting left of center, for the reasons described above.
Similarly, a barrel shoulder that bottoms out on the frame too late will leave the front sight angled towards the left, from the shooter’s perspective (towards 1 O’ Clock, when viewed from the muzzle end). This will result in bullets striking to the right of center, after the shooter makes his “corrections.”
Identifying the problem
Because a barrel clocking error can be subtle, it’s not always easy to tell if your barrel is off center. A gross misalignment is pretty easy to see, but most of the time a problem like that won’t be allowed to leave the factory. Usually, the problem is much more subtle, and it takes a hard look to determine what you’re dealing with.
The first place to start is to look at the revolver from the muzzle end. After unloading the revolver, leave the cylinder open, and examine the gun from the front to see if you can detect a clocking error. Does it look like the front sight is cocked off to one side or the other, with respect to the frame?
RevolverGuy friend Dean Caputo showed me a trick that can help with answering this question. If you take a straight instrument, like a ruler or a pencil, and hold it up against the underside of the topstrap inside the cylinder window so that it’s evenly centered, you can use it as a reference line to see if the front sight is cocked. A nicely-centered front sight will make a right angle with the pencil, but one that’s cocked off to the side will form an angle that is more than 90 degrees on one side, and less than 90 degrees on the other.
Another place you can look is the juncture between the barrel and the frame. If the barrel has any kind of grooves, sight ramp, or square profile on its top surface, you might be able to detect a misalignment where the barrel’s shoulder meets with the frame. A square shoulder that is too high on one side, and too low on the other, indicates that the barrel isn’t screwed into the frame properly, for example.
I’ve found that sometimes these subtle differences can be hard to tell with the naked eye, but they become more obvious when you see them in a picture, so it can also be helpful to prop your gun up, or place it in a vise, then snap a few pictures to help with your analysis. If you print the pictures out, you could even use a protractor to measure the angles, if you needed to.
Fixing the problem
The clocking error on the hose spigot that I mentioned previously was easy enough to fix, with a little bit of Teflon tape. Just a few extra wraps is all it took for me to eat up a little space on the threads and provide a tight fit, while still allowing me to put the part on straight.
Unfortunately, it’s not always that easy when we’re talking about a revolver.
If you have a revolver with an adjustable rear sight, then things aren’t too bad. You can simply run the rear sight to the left or right to fix your problem. If the clocking error is minor, then you should have more than enough travel in the rear sight blade to get the gun shooting straight. Personally, it would drive me nuts to see the rear sight pushed over to one side, but if you can live with it, then you can do good work with the gun set up like that.
Things become more difficult with a fixed sight revolver, however. Here, your fixes aren’t as simple as turning a screw, and involve some procedures that are fraught with the potential for making a very costly error.
The first you thing could try is to bend the front sight over, back towards the center. This was a relatively common fix on guns like the Colt Single Action Army revolvers, or the older Smith & Wesson revolvers with integrally-forged front sight blades, from what I understand. I remember a number of the Old Guard of writers—and some new ones, like John Taffin–describing how front sights were bent to fix windage problems. Taffin, as I recall, was pleased with the outcome on his samples.
But there are significant risks with this procedure. With guns like the older Colts, it’s very easy to break a front sight off completely at the joint in the sight’s key slot on the barrel. This would require you to silver braze the sight back on and reblue the gun—an expensive fix, for sure.
On the other guns, it’s just easy to screw up the job and wind up with a front sight that’s gouged or twisted (which will do you no good at all—you really don’t want to see the side of your front blade when you’re trying to aim), or leave a good scratch on your barrel.
Bending the sight is also contraindicated in some cases. It requires a relatively tall and thin sight blade, like the one found on the SAA, to get enough purchase on the blade to bend it. A gun with a short post (like a J-Frame), or a thick blade (like a modern ramp sight), could be very hard to bend without damaging the gun.
All said, there are much better methods of fixing the problem.
Doing some filing
One of these is to file your sights (usually the rear) to correct the windage error. This is probably easier to accomplish, and comes with less risk of breaking the gun, but it still has its own risks.
First, you have to understand which side to open up! The rule is that you want to open up the same side of the rear notch that the front sight is pointing towards. For example, if the front sight is angled towards the shooter’s right (towards 11 O’ Clock, when viewed from the muzzle end), then you’ll want to open up the right side of the rear notch to help “center” the angled front sight. Picking the wrong side will only make your problems worse, so make sure you get this part right.
Second, you have to remember the first rule of filing—it’s easy to take material off, but very hard to put it back on! Go slow with your file, keep it square, don’t take too much metal off, and check your progress frequently. Just a pass or two is all that’s usually required to relieve the notch enough to fix your windage issue.
If you have a blued gun, you’ll need to touch up the file work with a little cold blue to hide the shiny part, but a stainless gun shouldn’t need anything. If you do get a shiny edge that bugs you on a stainless gun, you could probably just smoke it with a match to dull it.
RevolverGuy Dean Caputo was kind enough to fix my S&W 640 in this manner, and I’ve been very pleased with the results. Dean used a file with a safe edge to avoid scarring up the bottom of the rear sight notch, and with a few small passes, he removed enough material from the right side of the sight notch to account for a barrel that wasn’t screwed in far enough by the factory (a common occurrence in J-Frames, in particular, it seems). As a bonus, my aging eyes have enjoyed having a little more light around the front sight, too!
The front sight can also be filed to correct a windage problem, if the misalignment isn’t too gross. If the front sight leans to the right, from the shooter’s perspective, then you can thin the starboard side of the front blade to make the sight picture look more balanced.
Go to the bar
Industry veteran Ed Harris suggests another popular method for correcting the problem is to strike the barrel shroud with a babbit bar, to turn the barrel ever-so-slightly in the frame. This is the method that’s taught at Smith & Wesson’s Police Armorer School, and it has also been used for corrections at Ruger.
A skilled person could probably make the necessary corrections with this method, but it’s probably not wise to give it a go on your prized heirloom the first time around. You’d also want to skip this method if you were dealing with a Scandium or Aluminum-framed gun, as they would be easy to damage.
As an alternative to whacking the gun with a lead bar, Ed says that some places have used a frame wrench and a barrel vise to allow the barrel to be turned with a little more finesse and precision. This was apparently the favored solution to fix tapered Colt barrels, back at the factory, using precision frame and barrel inserts that were specially-machined by Colt for the job.
Amateurs need not apply
The last method for fixing a clocking error is to remove the barrel and solve the issue that created the problem in the first place.
The reason that our barrel isn’t screwed in far enough is because the thread patterns aren’t timed properly, and the barrel’s shoulder hits the frame too soon for the front sight to be properly oriented. Gunsmith Jerry Kuhnhausen, author of the “Shop Manuals” which have become industry standards, describes how the frame and barrel surfaces will need to be cleaned up and trued to fix this interference issue and get the barrel timing right. Sometimes a ridge of material will build up on the front of the frame when the barrel is torqued into place, and this may need to be knocked down. Similarly, some material at the barrel’s shoulder may need to be removed to fix the issue and allow you to index the barrel properly. Both operations require some careful machine work to change the fit between these parts so that the barrel is both snug and perfectly timed, although Ed Harris suggests it could also be done with an India stone, some honing oil, and some patience.
Ed advises that during manufacture, some companies (like Ruger) use a special timing gage to check the barrel threads, which ensures the barrel threads are within tolerance. This usually eliminates the barrel as the source of a clocking error, leaving the frame itself as the culprit. If the front of the frame is a little too proud, then the properly-timed barrel will bottom out, and the barrel assembly fixture will reach its maximum torque value, before the front sight reaches TDC. This mismatch can be detected when the barrel is being hand-fitted to the frame as part of a pre-assembly test (a barrel that is screwed in until it is hand-tight should clock to approximately 15 degrees short of TDC, since the machine will torque it the rest of the way, so anything more than 15 degrees indicates a problem that needs to be addressed), and if it’s caught at this stage, then a few passes with a surface grinder can take enough material off the front of the frame to resolve the issue before final assembly. However, if an operator isn’t paying attention to tolerances, then the barrel will simply come up short of TDC at the maximum installation torque value, and your front sight will be cocked off to the right when you look through the sights.
It’s possible, but less common, that your barrel could be screwed in too tightly, as well. This can happen if the thread timing is off, or if the frame and/or barrel shoulders are not properly dimensioned. It can also happen if too much torque is applied during barrel installation, and the barrel is turned too far into the frame. In this latter case, Ed Harris advises that the barrel can suffer from “thread choke,” where material gets displaced in the bore underneath the threads, causing a constriction of the bore. Ed advises that over-torquing during installation can also cause stress cracks at the root of the barrel threads, which can be exacerbated over time and cause a barrel to crack completely off the frame—especially if the cracks are corroded by the use of chlorinated oils or solvents during manufacture or maintenance.
A barrel that has been turned too far onto a frame may have crushed or damaged the frame or barrel enough that it needs to be replaced. In some cases, a gunsmith could possibly repair the mating surfaces and reinstall the barrel properly, leaving the sight at TDC.
Experienced police armorer Dean Caputo notes that when clocking issues are corrected, it can result in barrel-cylinder gap (B/C gap) issues that need to be fixed as well. If a barrel is fully turned into the frame, this could narrow the B/C gap enough that the barrel extension would have to be relieved to restore the proper clearance, for reliability. If an over-torqued barrel is backed off, it could widen the B/C gap to the point that it’s beyond spec, and result in the need for a new barrel.
Fixing all of these problems is probably beyond the ability of the average gun tinkerer, and requires some real machining talent and a host of proper tools. Just getting the barrel off the frame without twisting or breaking the frame is a specialty job in itself, which requires special tools and techniques, so most of us are better off leaving this kind of work to a professional gunsmith or a factory warranty service.
This is actually the path that I advised my friend to take. Since his gun was brand new, and the misalignment of the barrel was substantial, I encouraged him to contact the Customer Service department at the manufacturer and ask them to repair the gun under warranty. Reputable manufacturers will make the process relatively painless for you, and will usually pay for the shipping as well (a good thing, since carriers like UPS will require the firearm to be sent via overnight service—an internal policy, sadly generated by issues with employee theft, in the past). They can easily install a new barrel or make the appropriate adjustments to your frame and/or barrel to get everything straight.
We should note that the increased use of two-piece barrel assemblies—once popularized by Dan Wesson–by manufacturers like Smith & Wesson and Ruger has simplified the installation of barrels at the factory, and reduced the probability of clocking errors.
In these setups, the exterior shroud is easily “timed” to ensure that the front sight rests at TDC, and the liner or sleeve that actually makes up the true “barrel” can be easily installed to set a proper B/C gap. RevolverGuy purists (like myself) may not appreciate these tensioned barrels for their cosmetics, but there’s no arguing that they simplify manufacture and largely eliminate clocking errors. There’s a good argument that they might enhance accuracy, too—something that we hope to investigate someday here in these pages.
Get it straight
There’s a lot of reasons why a new gun might not shoot straight, and not every windage problem in a revolver is due to barrel clocking. However, if you’re sure that your trigger press is good, the sights and/or barrel haven’t been bent, and the crown is in good shape, you might have a barrel clocking issue to investigate.
Azimuth errors are usually a result of the screwball behind the trigger, instead of the barrel not being screwed in properly, but the guys who make guns have bad days too! If you understand the problem though, you can get it fixed without too much drama, and have your revolver shooting straight in no time.
Have fun and be safe out there!