Diagnosis and Treatment of Common Gun Ailments (Part II)
by Bob Londrigan, as published in Front Sight Magazine, May 2004
In the last issue we covered how to diagnose and treat the first two types of gun ailments: ammo malfunctions and magazine malfunctions. This month, we’ll address the third category – gun malfunctions. This category covers any malfunction not solely caused by ammo or magazines. It includes failure-to-feed/failure-to-chamber, stovepipe jams, light primer hits, gun doubling/hammer falling to halfcock, failure to extract, parts breakage, spring induced malfunctions, and lube induced malfunctions. In the discussion of these ailments there will be some overlap of information because the root cause of a malfunction may be a combination of several factors.
When your gun first begins to malfunction and before you do any diagnosis and repair, step back to make sure you have not caused the problem yourself. Consider if you have recently changed anything on the gun or if you have changed anything in your normal shooting routine. If this is the first practice session since that change and you are having problems, then revert back to the gun setup prior to having the malfunction. If this solves the problem, then there is a strong possibility that it was caused by whatever you changed. Now you must decide if the change improved your shooting enough to justify going through the trouble of making your gun work with the new setup. In most cases, it will likely be best just go back to the old setup.
If you’ve ruled out recent changes you’ve made as the root cause, it’s time to go into diagnostic mode. Something has changed and you have to figure out what it is and what to do about it. Realize that all guns wear a little with every shot. Eventually most guns will wear enough to impact performance. If it’s not functioning like it was when it was new, your gun will have to be adjusted. Let’s look at some specific types malfunctions you may encounter and what type of adjustments to make for each:
Failure to feed/failure to chamber – “Failure to feed” means a round hits the bottom of the feed ramp and, thus, does not feed. A similar problem, “failure to chamber,” means a round hits the feed ramp, feeds partway into the chamber, but does not fully chamber. If a round hits the bottom of the feed ramp and stops, the culprit is usually the magazine and not the gun. In the last issue, we discussed how to solve this problem by tuning the magazines/springs. If the round feeds partway into the chamber and then stops, look to see how far up it is in the breechface. If it is not all the way up, check for excess extractor tension, a sharp edge on the extractor, or even a sharp edge on the firing pin hole that is catching the brass (the corner of the firing pin hole should have a slight bevel). If the round is at the top of the breechface and you rule out ammo problems, check for obstructions in the chamber. I have seen corn cob media or other debris get caught at the front of the chamber and prevent the slide from closing completely. This will also happen if debris is caught between the comp and the slide or in the top locking lugs on the barrel.
Stovepipe jams – There are two types of stovepipe jams: those caused by the brass hitting the port and those caused by brass hitting the scope/scopemount. To diagnose which type of jam you have, wrap the underside of the scope with a piece of masking tape and then paint the inside edge of the ejection port with black marker. Now shoot a couple hundred rounds through the gun. When you’re done, check to see if you have marks on the tape or on the port. Brass hitting the scopemount is really not a problem as long as it is not bad enough to cause a jam. If it is causing jams, tune your ejector to eject brass lower by moving the contact point up (as discussed in previous articles.) Brass marks on the port will usually be found at a point equal to the length of a piece of brass from the breechface. If brass is hitting the port, it is coming out too low and will likely cause bad jams on a regular basis. Tune your ejector by moving the contact point on the ejector a little lower. This will make the cases eject higher. Re-test the gun with the marker and masking tape to make sure you have corrected the problem.
Light primer hits – Light primer hits are usually caused by poor ammo. However, if you have ruled this out check for debris in the firing pin hole, a broken firing pin, or a broken firing pin stop. Removing debris and/or replacing the broken part should take care of the situation. You may also experience light primer hits if there is not enough overtravel adjustment on the trigger and this causes contact between the halfcock notch on the hammer and the sear.
Gun doubling/hammer falling to halfcock – There are several reasons your gun may double or fall to halfcock:
Failure to extract – Don’t confuse failure to extract with a stovepipe jam. Failure to extract is when there is an empty case in the chamber that the extractor did not remove. This malfunction is usually caused by a worn or broken extractor. Check the extractor hook to make sure it is intact and not worn. Replace or adjust the extractor if needed.
Mystery malfunctions - Other malfunctions can be grouped in a category called “mystery malfunctions.” Their mystery sometimes can make them very hard to track down. If you can’t find a cause for repeated malfunctions detail strip the gun and look for any part that is cracked or broken. A cracked slide, barrel lug, or barrel link will usually cause malfunctions before it breaks altogether. I have also seen thick oils/lubes cause malfunctions that were temperature dependent. One last thing to check is your recoil spring system. This component wears and can cause problems to appear out of nowhere. Replace your springs and see if the problem goes away.
Keep in mind that your gun is a finely tuned, precision instrument that is comprised of numerous components designed to function in one precise way. If any one component becomes worn or damaged to the point where it no longer performs or to where it adversely impacts the performance of another component, the gun will likely malfunction. By employing the diagnostic activities I’ve discussed in this and the previous article you should be able to pinpoint the problem behind a malfunction. At that point, either you or a competent gunsmith should be able to make necessary repairs and get you back to shooting trouble-free.