We'll assume, for the purposes of this exercise, the gun is in good working condition and relatively clean.
There are a number of different ways a semi-auto can "jam," and if you are considered knowledgeable of firearms and make such a statement to an expert, he is going to consider you a beginner, because "jamming" is actually the result of several different reactions to the mechanical actions occurring in the handgun. You should know these and be able to describe them properly. Not only will the expert be able to understand the problem better, he will instantly raise his estimation of you as a handgunner at least several notches.
The most common of these failures in a semi-automatic pistol can be described as one of these three events:
• Failure to feed. The bullet does not travel properly from the magazine to the chamber, and the slide closes only partially. When this occurs, with the chamber partially open or the slide not locked correctly into the rear of the chamber, the pistol is said to be "out of battery." This frequently results in the guide rod for the slide sticking noticeably out of the front of the gun.
• Failure to extract. The bullet fired, but the extractor did not pull the fired case from the chamber. Another round could not be fed into the chamber because of this. Sometimes this results in "double-feed" in which the fired shell is still in the chamber, and a live round has been picked up from the magazine and forced against the fired shell. The gun is out of battery with the slide partially open. The magazine may be stuck and will not drop.
• Failure to eject. The fired case is pulled from the chamber, but not fully ejected, causing the slide to lock partially open on the empty case. Sometimes the case is trapped by the slide and held in an upright position, the empty hull pointing upwards like the metal chimney of a stove, thus leading to the nickname of "stovepiping."
Taking them one-by-one, a Failure to feed can generally be attributed to any of several things - a dirty chamber, thus keeping the round from seating properly, or damaged magazine lips, causing the round to be misaligned as it is picked up by the slide and carried to the chamber.
Probably the most common reason for this malfunction is "riding the slide," i.e., holding onto the slide as it travels forward, reducing its forward speed. The slide does not have enough forward momentum to properly seat the bullet, and the gun will be "out of battery," or not completely closed.
On all semi-autos, pull the slide all the way to the rear, and let it go. The slide has to travel rapidly, even violently, to the forward position to properly seat the bullet in the chamber.
A failure to extract can be traced generally to one of several things - a dirty chamber (or dirty bullet case) makes friction hold the case with more strength than the extractor can apply, and the empty shell stays in the chamber. Another cause can be a damaged extractor - generally a claw-like device that clips over the bottom edge of the shell and pulls it out of the chamber with the rearward motion of the slide. Another common cause is termed "limp-wristing."
A failure to eject can also have more than one reason for occurring. It can be a damaged or faulty ejector - this is the piece that is located near the end of the rearward path of the spent shell, and causes it to kick out of the extractor with some force, causing it to fly clear of the pistol. Another, much more common reason is "limp-wristing."
Why your gun "jams"
Let's see. I noted three types of "jams" and seven causes of that series of actions, and one of those was repeated twice.
Of all the reasons for a pistol to "fail to function" (the proper terminology for what is loosely referred to as a "jam"), one of the most common is "riding the slide," which fails to seat the round properly. The slide does not lock forward (the gun is "out of battery") and the gun fails to fire.
The absolute most-common reason for a malfunction is a loose grip ("limp-wristing"), which causes the mechanical action to fail. The gun slips in the hand of the shooter, the slide moves only part way to the rear, short-stroking instead of traveling completely to the rear of the slide rails. The gun then fails to extract, or eject.
When a student comes to us with a complaint of their gun "jamming" a lot, we can generally attribute the problem to improper grip.
Sometimes, the pistol in question is on the lower end of the economic scale, and at the risk of hurting their feelings, we ask them if they really want to trust their lives to a piece of junk, for which they all too often have paid an exorbitant price.
But digressions and preaching about junker guns aside, we will take the gun, stick a fully loaded magazine in it and almost always empty the magazine into the target with no failure whatsoever.
Turning and handing the befuddled student his now-empty gun with the slide locked back, we'll tell him, to the great delight of his buddies, "You're 'limp-wristing' the gun."
A semi-automatic pistol operates off recoil, right? The rearward "kick" of the shell being fired forces the slide backwards. When the slide goes backwards, several actions are initiated to make the gun ready to fire again.
As the shell fires and the bullet travels out the barrel, the claw-like extractor pulls the spent case out of the chamber, ripping it backwards with the rearward motion of the slide. As it travels backwards, the ejector forces it out and away from the extractor, causing it to pop from the slide and clear the gun.
The slide continues on its rearward path until the very powerful recoil spring, being compressed by the rearward push of the slide, builds energy that overcomes the rearward motion of the slide and forces it back in the other direction. As the slide comes forward, it picks up a fresh, unfired shell and forces it out of the magazine lips, up a feed ramp and into the chamber.
The slide locks itself in the forward position, the gun is cocked, and it is ready to fire again. You only have to pull the trigger to initiate the sequence all over again.
The gun operates on recoil, right? Therefore you must have a firm platform for the pistol to operate from, or you are negating the effect of the recoil. You are causing the gun to fail to function - it isn't the gun's fault!
Any gun can have mechanical problems that can cause a failure to function, but ask any instructor on any range anywhere the main reason semi-automatic pistols fail to cycle, and he will invariably grin and say "limp-wristing."
You actually should control the trigger on a semi-automatic pistol in a different manner than a revolver. You use the tip of your finger to fire a semi-auto, rather than the full finger needed to manipulate the longer trigger pull of a revolver.
If your pistol is a double-action-only semi-auto, you may need the strength of the full finger to make the longer trigger pull. As with all tips and techniques, there are exceptions, and this is one. You should practice with your gun and learn your trigger.
The two most important shooting fundamentals for accuracy are sight alignment and trigger control; you learn both of these by shooting the gun regularly.
The most important thing you can do is practice; shoot often in a safe environment such as a range, and concentrate on improving your skills, rather than just pulling the trigger and burning ammo. This practice might save your life some day.