The Pencil Test

Imagine you're looking at a used pistol with an intent to purchase it. If it has been well used, chances are that some parts may be worn out or broken. One part, in particular, is the firing pin, which may be broken, bent, blunted etc. Another part of interest is the mainspring, which may have lost some of its strength. Or perhaps you stripped your pistol in order to clean it, and you aren't sure if you put it back together properly. There is a simple test to verify that the firing pin and mainspring are working satisfactorily and this test is the pencil test, which we will study about today. The only tool you'll need to conduct this test is a pencil with an eraser tip on one end:

A standard #2 size pencil. Click on the image to enlarge. Public domain image.

1. First, make sure the pistol is empty.
2. Cock the pistol, making sure that it is still empty.
3. Insert a pencil with the eraser end first into the barrel and push it as far as it will go (do not force it, just push it in gently). For best results, use a new wooden pencil (such as a standard #2 size pencil, like the one pictured above), with the eraser in good condition
4. Hold the pistol vertically, with the barrel end aimed upwards.
5. Make sure that the pistol is indeed empty, then pull the trigger.
6. If the firing pin and mainspring are working correctly, the pencil will move noticeably. In many pistols models, the pencil will actually come shooting out of the barrel. If the pencil doesn't move, or only moves weakly, there may be a problem with the firing pin or mainspring.

This test works on various pistol models, both hammer-fired and striker-fired types. Of course, the distance that it comes shooting out of the barrel depends on the model of pistol and also the wear and tear of the parts. For 1911 pistols in good condition, the pencil should come flying out and go at least a few feet up in the air. Glock pistols will also propel the pencil out a good amount of distance, but generally not as far as a 1911. Of course, the test also depends on the shape of the firing pin and the hardness of the eraser. For instance, in some models of M&P pistols, the firing pin may pierce the eraser instead of shooting it up. In such cases, if the pencil is put in with the unsharpened end in first, it may come flying out better. Alternatively, a plastic ballpoint pen, such as a Bic, may be used. In general, hammer fired pistols tend to propel the pencil out farther than striker fired models.

For pistols that are equipped with decocking levers (such as Sig Sauer, Ruger P95, Beretta M9 etc.), a similar test may be used to ensure that the decocking safety mechanism is working properly. As before, the pistol is cocked and the pencil is pushed in as before and the pistol is held vertically. Then, instead of pulling the trigger, the decocking lever is pushed instead. If the decocker is working correctly, the pencil should not move at all. If it moves, that means the decocker is not working properly and the firing pin is contacting the eraser.

Now on to some videos, so that you can see what it looks like.

The first video is from user Sadie Thorne on youtube and shows a quick test with a 1911 type pistol.

This video comes with no explanation, but shows the test very nicely. Notice how far the pencil comes flying out of the barrel, when the trigger is pulled.

The next video is by stdlfr11 and shows the same test done using a CZ-75 pistol.

This video has the user giving an explanation of the test, as it is being done. Note that while the pencil moves noticeably, it doesn't move as far as the one in the previous video. The reason for this becomes clear when the user pulls the pencil out as you can clearly see the indentation that the firing pin made on the eraser, which could explain why it didn't fly out as much. If the eraser had been harder or if the user had put the pencil in with the unsharpened end first, it would probably have flown out of the barrel much better. The test does show that the firing pin is functional and is not broken.

So there you have it, a simple test using a pencil ensures that the firing pin and mainspring are working satisfactorily.

How do Firing Mechanisms Work - III

In our last couple of posts, we saw a couple of examples of semi-automatic, full automatic and three round burst mechanisms. The first video was prepared by the US Army to train soldiers. As it turns out, the Army had actually prepared a set of videos. The first in the series showed an example of a bolt-action firearm in action. We will study that video in today's post:

Interestingly, the video shows a hammer fired and a striker fired mechanism and also deals with extraction and ejection mechanisms, as well as loading new ammunition from a box magazine.

Happy viewing.

Hammer Fired vs. Striker Fired

In the world of modern firearms which use centerfire cartridges, there are two major types of mechanisms used to trigger the cartridge primer. One uses a hammer and another uses a striker. Therefore, mechanisms that use a hammer are called hammer-fired and the ones that use a striker are called striker fired. As you can guess, each mechanism has its own group of supporters. In today's post, we will study what this all means.

In a hammer fired mechanism, the hammer is a heavy piece that is allowed to rotate about a pivot point. When the hammer is cocked, it compresses a spring. When the trigger is released, the spring pushes the hammer and forces it to rotate forward. The end of the hammer strikes the back end of a firing pin, which is a thin steel pin with a hardened tip. The front end of the firing pin strikes the primer of the cartridge, thereby detonating it. The image below shows how this works.

In some revolvers, the firing pin is attached to the hammer directly.

Firing pin attached to the hammer of a Smith & Wesson Model 13 revolver.

Image licensed under Creative Commons Attribution-Share Alike 3.0 Unported license.

In either case, the key part of the mechanism is a rotating hammer mechanism. Here's another animation showing the same concept.

The main thing that we conclude after looking at all the images above is that a hammer-fired weapon is a rotating type mechanism.

In contrast to this, striker fired systems operate in linear fashion. The striker is a part that is a bit heavier than a firing pin and it is directly connected to a spring. When the firearm is cocked, the striker is moved against a linear spring and held in position. When the trigger is released, the spring forces the striker forward with enough energy to detonate the primer upon impact. The animated image below shows how this works.

The striker is the long part in the back of the gun that looks like this:

It should be noted that the animation example for a striker fired weapon shows the firing mechanism of a Glock pistol. When a Glock is cocked, the striker is moved back and held under partial spring compression by the trigger mechanism and safety devices. As the trigger is pulled, the striker is initially pulled back till the spring reaches full compression and then the striker is released. In other pistol models, such as Springfield XD or Smith & Wesson M&P models, the striker is already held at full spring pressure when it is cocked. Pulling the trigger in such firearms merely releases the striker and allows it to fly forward

From the above images, we see that hammer fired mechanisms use a rotational force to detonate the primer, whereas striker fired mechanisms use a linear force to do it.

Striker fired mechanisms tend to have fewer parts than hammer fired mechanisms and are therefore simpler. However, they take up a bit more room. This is why firearms that don't have bolts, such as revolvers, use a hammer-fired action. Revolver and many types of single-shot action firearms generally don't have the room to accommodate a striker mechanism.

Strikers are commonly found in many modern semi-automatic pistols, bolt action weapons and shotguns. In fact, the first striker fired weapon invented was a shotgun invented by Daniel LeFever in 1878. Another example of a striker fired weapon is the Czech vz.58, which we studied earlier (contrast this with the similar looking AKM rifle, which uses a hammer fired mechanism). Striker fired pistols started becoming popular in the 1980s, when Glock started using them on their pistols. However, it must be noted that Glock weren't the first to use it on pistols either: John Browing used it in the .25 caliber Model N pistol and the H&K P7 is striker fired as well. Nevertheless, once Glock started becoming popular, other manufacturers also started using the same idea on a larger scale and now you have several pistol models, such as Smith & Wesson M&P, Springfield XD, Ruger SR9 etc. However, there are some famous pistol models that use a hammer fired mechanism instead. Examples include the Colt M1911, Browning Hi-Power, Beretta M9 etc.

A striker fired mechanism doesn't have an exposed hammer, so it cannot get caught in clothing, shrubs etc. The fact that it has fewer parts means easier maintenance as well. Another positive is that it has a consistent trigger pull for every shot (in contrast to double action/single action hammer fired mechanisms, where the trigger pull force is different depending on whether the firearm is working in single action mode or double action mode). Striker fired mechanisms generally have a consistent trigger reset as well.

On the other hand, if there is a malfunction on a striker fired weapon because the primer didn't detonate, the only option is to eject the cartridge and try the next one. With a hammer fired firearm, it may be possible to try again on the same cartridge (on models that provide this second-strike capability). Hammer fired guns also generally impact primers harder than strikers do, thereby giving a better chance to detonate them. It is for these reasons that many military forces prefer hammer fired weapons. For example, the US military's choices of weapons: Colt M1911 pistol, Beretta M9 pistol, M1 Garand, M14 rifle, M16 rifle, M4 carbine etc. are all hammer-fired.

The video below shows some of the advantages and disadvantages of each system:

As you can see, each mechanism has its own group of fans that argue about which is better. Happy viewing.