Diagnosis and Treatment of Common Gun Ailments (Part 1)

by Bob Londrigan, as published in Front Sight Magazine, March 2004

In previous articles, we’ve looked at preventing reliability issues by correcting situations that can lead to poor reliability.  However, sooner or later you are going to encounter a malfunction for which you cannot find a cause.  When this happens, good diagnostic skills will be crucial to correcting the problem.  Whether you try to analyze the problem yourself or end up explaining it to your gunsmith, you must understand the nature of problem that is causing the malfunction before it can be corrected.  Also, an incorrect diagnosis may cause you to change the wrong thing and, thus, make the problem worse. The focus of this article is on properly diagnosing your gun’s reliability issues by using the type of malfunction as a guide.

Let’s first define a standard for reliability.  My standard is that I want to be able to fire at least 5,000 rounds without having any type of malfunction that I cannot easily explain.  This means that if I do have a malfunction, I want to easily be able to determine its source or root cause. If it is something I can correct quickly, then I correct it and don’t worry about it.  If I can’t, then it’s time for gun diagnosis and treatment.  It is important to be able to quickly diagnose what is going on because it will enable you to spend more time practicing and less time working on your gun.  Most malfunctions will be related to either ammo, magazines, or your gun. 

 Ammo Malfunctions

Let’s begin by examining ammo malfunctions.   Ammo malfunctions include light primer strikes, failure to chamber, and failure to feed (this could also be a magazine malfunction.)

Light Primer Strike:  Light primer strike can be caused by high primers, primer flow, or obstructions in the firing pin channel.  Check for high primers by placing a loaded round on a flat surface.  You should not be able to rock the round back and forth.  If you can move it at all it means the primer is high.  The primer should actually be seated about 0.003-inch below the level of the case.  If you put a straight edge across the back of the round, there should be space between it and the primer. To correct high primers, readjust your loader or use more pressure to seat the primers.  Before a match, check all your rounds for high primers when you chamber check your loads.  If you are still getting light primer hits and you know your primers are not high, then look for primer flow, trigger/hammer/sear malfunctions, or obstructions in the firing pin hole (such as pieces of broken firing pin spring or primer flow). 

Primer Flow:  Primer flow is usually caused by excess pressure.  Look for a shiny ring around the outside of the impression made by the firing pin.  When a primer flows it flows into the firing pin hole.  As the round is ejected, the flow is scraped off and ends up in the firing pin hole as a small ring of metal. This ring will then drag on the firing pin.  It can slow down the firing pin enough to cause light hits on the primer.  I have heard many a competitor say “but it is only a little flow.”  There is no such thing as a “little flow.”  One primer that flows may eventually cause a jam.  Although it probably won’t, why take the chance?  Readjust your loads or switch powders.  Then re-chrono and check again for flow.  Repeat this process until you have a load that makes major without any flow whatsoever.  It also helps to periodically clean your firing pin hole with a pipe cleaner.  This is one of the items I keep in my range bag just in case.  I also have seen situations where altitude or heat produced enough changes to make a load that was previously fine cause primer flow.

Failure to Chamber:  Failure to chamber can be caused by many factors such as ammo that fails the chamber check, high primers, debris caught in the chamber, out of spec brass, a too tight or not properly fit extractor, or even the overall length (OAL) of a cartridge. When you have a round that does not chamber completely, set it aside and check it after practice.  At the time it happens, check to make sure there is nothing caught in the chamber.  You might want to strip the gun and look in the chamber.  Try dropping several bullets in the barrel to see if they drop in freely.  If they don’t, you’ll know there’s an obstruction that needs to be removed.

If a round does not chamber during a match, see if you can find the round that you ejected during the stage.  Later check the round for the following:

·        See if it will chamber check.

·        Make sure it was properly crimped.

·        Check the OAL to make sure it meets the specs for your load.

·        Look for high primer.

·        Make sure the brass is not too long.

If the round fails any of these tests, then you know it was your fault and not the gun’s.  You should re-check your loading and case preparation procedures. If the gun passes all these tests, you need to check your extractor tension to make sure it is not too tight. If that seems OK, there is one last thing to check.  Make sure the brass is not catching on the firing pin hole and that there is at least 0.062-inch clearance between the extractor hook and the breechface.  If it passes these checks, then it might be time to send it to your friendly gunsmith (you do have a gunsmith, right?)

Failure to Feed:  Although failure to feed is usually a magazine problem, you first want to rule out the ammo.  Make sure that none of the rounds in the offending magazine are too long or have not been crimped.  Set the offending magazine aside and measure all the rounds after practice. If you have ruled out the ammo, it is most likely the magazine is causing this problem. 

Magazine Malfunctions

Magazine malfunctions can include failure to feed, ejection problems (every once in a while), and magazines that do not drop free.

Failure to Feed:  If a round fails to feed because it hits the bottom of the feed ramp and stops, it is almost exclusively caused by the magazine and not the gun. Any round that hits the bottom of the ramp is likely to cause a stoppage at some point.  Failure to feed stoppages that occur after the round has started to chamber have other causes and are not usually related to the magazine (we will talk about this kind of stoppage later.) If you are getting hits on the bottom of your feed ramp, make sure you have fresh magazine springs and that your followers are tightly attached to the springs.  Inspect the springs for kinks or bends that were not there before.  Measure the outside dimensions of the magazine as well as the feed lips.  Compare these dimensions to a magazine that works well.   If you’re really on top of it, you will have recorded the dimensions of the magazine when it was working.  If you find that something has changed, fix or replace the magazine and then test again. 

Ejection Problems:  Every once in a while I see a magazine cause an ejection problem.  Check the top, front, right corner of the magazine lips (as viewed from the back). If this point is too high sometimes you will get contact with the brass that is ejecting.  Look for brass marks on the magazine at that point.  Grind a little off the magazine until you no longer get brass marks or re-adjust your ejection angle higher. 

Magazine Not Dropping Freely:  For magazines that do not drop free, first check to see if this is being caused by the magazine release pushing the magazine sideways and pinning it in the gun.  Hold the magazine release all the way in and see if the magazine sticks.  Then release the magazine button slowly. If the magazine drops as you are releasing the button, you will need to trim the inside of the magazine release where it contacts the magazine when the button is fully depressed. If the gun passes this first test, then squeeze the grip tightly while simultaneously pushing in the mag release. If the magazine sticks, then release the squeeze.  If the magazine releases as you soften your grip, then you are close and probably need to change the dimensions of the magazine only a bit.  But if the magazine still sticks, you may have to substantially change the dimensions. Check to see where the magazine is binding.  Coat the magazine with magic marker and then move it around in the gun.  See if it is sticking front-to-back or side-to-side by checking where the marker has rubbed off.  Then use some careful pressure from the vise to slightly alter the magazine’s dimensions.  Measure before and after squeezing, and go slowly until the magazine starts to drop free.  If you have to change the dimensions too much, it might be better to just buy another tube.

Gun Malfunctions

Lastly, there is the issue of gun malfunctions.  They include failure to feed, failure to chamber, stovepipes that hit the port, stovepipes that hit the scope, light primer hits, gun doubling, hammer falling to halfcock, failure to extract, parts breakage, lube malfunctions, and weak ejection.  As you can see, this topic requires extensive discussion.  Look for it in the next issue of Front Sight magazine.