Ask Foghorn: Snap Caps?

Texas Deputy asks:

I know that some makers explicitly state that dry firing is safe, and will not damage the firing pin and related assemblies, but others strongly recommend snap caps for repeated dry firing.

What is your stance on snap caps?

This is actually a pretty easy one, so let’s jump right in. . .

Dry firing is the practice of pulling the trigger and letting the hammer hit the firing pin in your firearm without having a live round in the chamber. Because there’s nothing in the gun (the gun is “dry”) nothing goes bang, but everything else about the gun (the trigger pull, ergonomics, etc) is the same as if it were loaded. Dry firing is a great way to practice sight alignment and trigger pulls on firearms without spending a single penny on ammo.

I follow a 70/30 rule on firearms practice — 70% dry fire, 30% live fire. Dry fire practice is a great way to develop the fundamentals but at the end of the day, you really need to put rounds downrange to test your skills.

The problem: dry firing has the potential to ruin your gun.

Firearms are designed to be used live and loaded. When a designer is figuring out how the firing pin and hammer assemblies work in a gun, they assume that there’s a live round in the chamber. That means the firing pin meets resistance in the form of a primer as it moves forward. The energy of the hammer falling is transferred through the firing pin and on to the primer where it ignites the primary charge and sets off the round.

When the firearm is dry – as in empty – that primer isn’t there to absorb the extra energy from the hammer. So instead of most of the energy being transferred to an external component designed to use that energy, it needs to be transferred to something else in order to stop the firing pin and keep it from flying into the chamber.

Designers typically include some sort of system in the firing pin channel or on the firing pin itself that stops or arrests the forward movement of the firing pin, absorbing that extra energy as it brings the firing pin to a stop.

On an AR-15, that arresting system comes in the form of the chunky flange on the rear of the firing pin, shown here disgustingly coated with carbon. When the firing pin moves forward, that flange impacts the rear of the firing pin channel in the bolt carrier and keeps it from moving any farther forward. The flange is so chunky because it needs to absorb all of the extra energy from the gun’s hammer and transfer it to the bolt carrier (a chunkier piece of metal more capable of absorbing the energy).

The act of arresting a firing pin puts a tremendous amount of strain on the metal due to the magnitude of the forces in play. It may not seem like a lot of energy, but we’re talking about tiny pieces and it’s certainly enough to crack or break the metal over time.

That’s why many of the modern firearms have easily replaceable firing pins — especially the M1 Garand, M1 carbine and M16. All three of these weapons use an arresting system that eventually wears out the firing pin and can cause it to break. As a result, they were designed to make those parts easily replaceable by the soldier. In a time when every single part of a military firearm had proof marks and a serial number, the M1 Garand and M1 carbine had no such markings on their firing pins and extractors for this very reason.

Most centerfire rifles and handguns have an adequate arresting system and easily replaceable firing pins, but rimfire firearms are another matter. Their components are much smaller than their centerfire counterparts and therefore are much more likely to break, even with an adequate arresting system. They need something in the chamber that will allow them to safely transfer the forward energy of the firing pin to a more robust piece of metal. That’s where snap caps come in.

Snap caps emulate the primer of a live round, whether it’s a centerfire or rimfire cartridge, and allow the firing pin to dissipate its energy in a safer manner.

You physics fans out there will remember that force equals mass multiplied by acceleration. So the more time something takes to slow down (or lose energy) the less force will have acted upon it. Or something like that. Anyway, the key concept here is that by distributing the application of force over a longer period of time, firing pin undergoes less stress.

Snap caps allow the firing pin to dissipate its energy over a longer period of time due to their design — specifically the placement of some malleable material where the primer should be. So rather than the firing pin striking the hard surface of the chamber or some other arresting mechanism designed to immediately stop the firing pin (think flying egg versus brick wall) the snap cap will slow the firing pin down before bringing it to a complete stop (think flying egg versus a soft fluffy wall of pillows…or Snooki).

Personally, I can’t think of a reason not to use a snap cap when you’re dry firing. Even if you have a modern firearm made from the best materials, you’re still putting wear on those parts and that will eventually lead to them breaking. Admittedly it might be centuries before that happens but hey, it’s possible!

If you’re still too cheap not to practice with snap caps, here’s a list of firearms that should probably never be dry fired without a snap cap:

  • Rimfire firearms: The mechanical bits are just too small to stand up to much abuse, and if you don’t treat them right, they will eventually crack and need to be replaced. And trust me, replacing a rimfire firing pin is not a task to be taken lightly.
  • Older firearms: 1980 is the year I have in my mind for when this starts applying, and ESPECIALLY anything made during WWII. Older firearms may have been manufactured using substandard materials and therefore often have more brittle firing pins and related parts. The caveat here is that if your gun costs less than $100 (AKA Mosin Nagant) and has no sentimental value I wouldn’t worry about it too much.
  • Rare firearms: If there’s only three of your model gun ever made, then there’s a good chance that you’ll never be able to find replacement parts. You might want to baby it a little bit more than the rest of your guns.

Modern firearms (rifles especially) are typically good to go for dry firing, but I’d never chance it with any of those three categories.

Sorry for the delay for those of you still waiting for your question to be answered — I just settled into my new place here in San Antonio and I’ll be getting to work on that question queue ASAP. Really.

If you have a topic you want to see covered in a future “Ask Foghorn” segment, email guntruth@me.com.

To browse previous Ask Foghorn segments visit http://www.thetruthaboutguns.com/category/askfoghorn/.

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About Nick Leghorn

Nick Leghorn is a gun nerd living and working in San Antonio, Texas. In his free time, he's a competition shooter (USPSA, 3-gun and NRA High Power), aspiring pilot, and enjoys mixing statistics and science with firearms. Now on sale: Getting Started with Firearms by yours truly!

31 Responses to Ask Foghorn: Snap Caps?

  1. avatarRobert says:

    And where does one get these mythical rimfire snap-caps used for dry firing?

    All the ones I have found clearly state “Not Snap Caps, Do Not Dry Fire” on the package.

  2. avatarFred says:

    I use snap caps for dry firing in all by my rimfire firearms.

    As the only rimfire firearms I own are a couple Ruger 10/22s and MK II & III pistols it is easier to just buy the entire bolt assembly with firing pin already installed. Cost is negligible for factory parts.

  3. avatarmichael says:

    What about using a spent casing? Is that OK?

    • avatarChaz says:

      For center fires popping out the old primer and then cutting down a pencil eraser to fit that hole is said to work well. Maybe just a glob of rubber cement, silicone caulk, etc. wiped to be flush with the base could do the same thing.

    • avatarDon Curton says:

      1) Snapcaps are generally a different color to help visually ensure you’re not loading a live round. You know, for safety. A spent case with no lead in it might serve the same purpose, but it’s one step closer to a live round. Once the “spent” brass case in in the chamber – there’s no good way to tell the difference between the spent case and a fully loaded case. Could lead to an “oops” moment later on.

      2) if you’re shooting an automatic, the best way to load a round into the chamber is from the magazine. That way the back lip of the cartridge slids up into the extractor as it loads. With a spent cartridge, you can’t do this because without the rounded bullet profile on the front it will jam. You could just put the empty cartridge in the chamber and them drop the slide, BUT the the extractor must bounce over the cartridge lip at full force. That’s a damn good way to break the extractor. Before this here Internet thing, some of us found that out the hard way.

  4. avatarxpo172 says:

    “Personally, I can’t think of a reason not to use a snap cap when you’re dry firing. ”

    Here are two:
    They eject every time you cycle the slide
    They cost less the zero

    Snap caps are useful, but if my XD breaks because I was dryfiring, I’m gonna call them for warranty parts. I’m not buying the “Firearms are designed to be used live and loaded” bit. Everyone dryfires their guns. Or should. And I think manufacturers know that and have built guns that can handle it.

    • avatarDirk Diggler says:

      +1

    • avatarMax says:

      I thought so too…

      Until I got a Ruger LC9. The trigger was a bit stiff so I spent some time dry firing it in hopes of smoothing out the trigger. After about 2 weeks of nightly dry fire (20-30 x/night) I suddenly had something fall out of the mag well… the firing pin came out in 3 pieces.

      Ruger was great about the replacement, but I learned my lesson. As always, YMMV. :)

  5. avatarJoseph says:

    I guess if one does a whopping 70% of their practice dry firing this all makes sense, otherwise, not so much. Fifty years of shooting, hunting, and carrying a gun for a living I’ve seen exactly ONE broken firing pin. On an S&W .38 special city issued gun. It belonged to my partner, and I do believe it was defective anyway. I could be wrong. But, I reckon I did most of my practice with live ammo, or just didn’t feel the need to pull the trigger every time I ‘practiced’ outside of the range.

    Too many engineers trying to figure out if the glass is half full…Although Don does have a good point about dropping a slide on a loaded round. Does tend to hurt the extractor if you do it over and over and over again.

    I never cease to be amazed at how difficult people try to make the firearms thingy. Must be all the lawyers…..

  6. avatarMatt Gregg says:

    I’ve hear that you shouldn’t dry fire a rimfire gun because there is a potential for the firing pin to strike the shoulder of the chamber or something like that

  7. avatarUtahLibertarian says:

    “Personally, I can’t think of a reason not to use a snap cap when you’re dry firing. ”
    http://findarticles.com/p/articles/mi_m0BTT/is_2_37/ai_n58532599/

    Clint Smith thinks it’s a safety issue. He doesn’t make a very strong case, and I’m not sure I agree with him. But he is Clint Smith.

  8. avatarRepresentative Carolyn McCarthy says:

    I dry fire all the time, without snap caps. I’ve only ever used snap caps to train loading or clearance drills.

    Firearms are mechanical. Firearms break. The best way I’ve heard it explained is this, when I was young and at Camp Perry shooting smallbore: “If your firing pin is going to break, it’s going to do it regardless of whether there’s a round in the chamber.”

    I’ve dryfired my guns ever since I started owning guns and have never experienced any broken firing pins. The only mechanical failure any of my guns has had is that the mainspring on my CZ-85 snapped, rendering the gun inoperable. I was dryfiring it. The gun would have failed regardless of whether I was shooting live ammunition or not.

    • avatarMatt in FL says:

      I suppose it depends on what you’re shooting. On a Springfield XD(M), it’s not the firing pin itself you’re worried about. Here’s a picture of one. That channel cut down the middle of the pin is for a firing pin retaining roll pin that’s driven through the top of the slide, through that channel, and into the bottom of the slide. When the gun is dry-fired, the back of that channel slams into that roll pin. Eventually that could lead to a bending of the pin, making it hard to remove/reinstall, and eventually, possible breakage of same. I know roll pins are cheap and easy to get, but so are a lot of other things that break at the worst possible time, and being easily replaceable makes it no less irritating when it happens. If a couple bucks worth of aluminum and plastic can prevent that from happening, it’s worth it to me.

    • avatarTim McNabb says:

      Mrs. McArthy, I am always glad to see your comments.

  9. avatarFord says:

    I don’t use snap caps when I dry fire. I mix them with live rounds in my magazines so that I can train myself not to flinch when I shoot. It works wonders for new shooters too.

  10. avatarRalph says:

    Check the manual that came with the gun. If you bought the gun used without a manual, you will be most likely be able to find a manual for the gun online. Check the manufacturer’s website first, and then check the other websites that offer manuals online for no fee. There are several.

    If the manual says that dry fire is okay, it’s okay. If it says otherwise or it’s silent, or if there is no manual available, then it’s not okay. For example, the Ruger 10/22 manual states “[t]he rifle can be “dry fired” for practice as long as it is empty and pointed in a safe direction.”

    As computer guys used to say, when all else fails, read the manual. Once you get past all those “warnings” in red agate type, there’s some useful information in there.

    • avatarRobert says:

      +1 for Ruger

      My 22/45 also has a cutout where the firing pin would strike the shoulder.

      It’s also retarded easy to change the firing pin on the 22/45, although it is a heavy chunk of metal for something supposedly delicate. I can’t see this thing breaking, and mine hasn’t after a decade and untold thousand rounds and dry fires.

      That said, I’ve been looking for 22 magnum snap caps forever for my PMR-30 as that firing pin seems likely to break after dry fire drills.

      Hence my earlier post.

  11. avatarsdog says:

    i have Azoom brand snap caps for all of my guns, and i use them every time i do dry fire practice. they are not super cheap, but they pay for themselves in the life cycle of your firearm’s internals.

  12. avatarAharon says:

    I spoke with two Ruger techs both of whom informed me that it is fine to dry fire the SP101 frequently. However, not to use snap-caps since using them with frequent dry firing can possibly produce a ‘drag’ on the cylinder.

  13. avatarTom says:

    Nice article. Back in the bad old days I was told as a kid not to dry fire guns as it would break the firing pin. Of course, this was long before 1980, and sort of pertained to guns manufactured prior to WWII of which I was given to shoot.

  14. avatarnitefly says:

    The act of arresting a firing pin puts a tremendous amount of strain on the metal due to the magnitude of the forces in play.

    This is really dependent on a lot of factors, and is a relative statement. My engineering sense tells me that modern metallurgy and design tools have enabled engineers to create firing systems that have fatigue lives far greater than what most, if not all of us, could achieve. You did allude to this near the end, so kudos.

    Also, I would hope any current designer/engineer would take into account dry firing as a a typical mode of operation when developing a firearm.

    + another 1 to checking the manual

  15. avatarArmsControl says:

    Ordered snap-caps for a 380 auto and received a 5 pack of Snap-Caps.

    Although the package makes a great claim of CNC precision 1 of the 5 snap caps is irregular and is more likely a .40 ACP. It is clearly over size and since 5 are required for use in the .380 ACP revolver these are intended for I am left with no more than I started with.

    The dealer I got them from states that he is seeing a great number of these like this. The dealer contacted Lyman (who make them) and after 3 weeks I am still waiting for a usable 5 for this revolver..

    This is just one example of just how “POOR” our manufacturing quality has fallen in the US and we need to step up to the plate. We are not gonna get out of this recession if we continue to sell inferior and defective products. Especially with items that are intended to provide a level of security and trust in quality.

    GET IT TOGETHER LYMAN!!!!

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