A Taxonomy of Safeties

There are several kinds of safeties that are used on service weapons to ensure that only the proper and deserving people are shot. They generally interface in some way with the firing mechanism of the firearm. They may act on the trigger, the hammer or striker, or the sear, or (in some fiendishly clever arrangements) more than one of the above. It is generally thought better to positively lock the striker or firing pin than merely to lock the sear or trigger. If the mechanism fails due to parts breakage, it is easier to design a fail-safe mechanism if the striker or firing pin is immobilized.

Safeties Classified by Operator Volition

Safeties can be classified based on the degree of volition required to use them. An applied safety must be consciously put on, in most cases. An automatic safety is unconsciously applied as the pistol is taken up. Examples of automatic safeties include:

  1. the Glock Safe Action trigger and its many copies and derivatives;
  2. the grip safeties characteristic of many Browning designs, such as the M1911 .45 and the FN M1910 pocket pistol;
  3. similar grip safeties on open-bolt submachine guns such as the Madsen and the Uzi. (An open-bolt SMG poses peculiar safety problems);
  4. transfer-bars and other means to ensure a weapon can’t fire unless the trigger is pulled;
  5. mechanisms that hold a firing pin back until a weapon with a locking breech is fully in battery (the disconnector often does double-duty as this part);
  6. Firing-pin immobilizers as in the Colt Series 80 and newer M1911s (an earlier firing pin safety, the Swartz Safety, was used in commercial Colt 1911s from circa 1937 to 1940, and is used by Kimber today);
  7. A heavy, smooth trigger pull such as that on a traditional Double Action revolver or a DA/SA autopistol can prevent unintentional discharges. However, some heavy triggers (like the Glock NY2) have a bad enough effect on accuracy as to threaten bystanders with unintentional shooting.
  8. Magazine safeties, an obsolete European concept;
  9. Half-cock notches (in British/European English usage, these may be called half-cock “bents.”)

Contrasting with these automatic safeties, that do their work without conscious application by the operator, there are Applied or volitional safeties. Applied Safeties are usually classified by what part of the firing mechanism they work on, and so examples of Applied safeties break down into:

  1. Safeties that lock the trigger. The simplest of these are the crude trigger-blocking safeties on an SKS or Tokarev SVT. More complex trigger-locking safeties are found in the AR series of rifles and the FN-FAL;
  2. Safeties that lock the firing mechanism (which may be further divided into those that lock the firing pin, like the Walther P.38 or Beretta M92, and those that lock the hammer, like the US M1 Rifle, or
  3. The bolt holding notch in many 2nd-generation submachine guns. (These are reminiscent in a way of the safety of the Mosin-Nagant rifle, which requires the cocking piece to be rotated and caught in a notch). The case can be made that this is a firing mechanism lock, because the bolt with its fixed firing pin is the firing mechanism.
  4. Safeties that lock the sear. Examples include the .45 M1911, its younger brother the BHP, many other auto pistols, and most general purpose machine guns. Some require the weapon to be cocked to lock the sear, others allow locking the bolt forward (the RPD LMG and the Sterling SMG are examples of this).
  5. Safeties that disconnect the trigger from the sear. This is found in the Bren gun and many other Czech designs, historically. The ZB 26 and its derivatives were quite cunning: in one position, the selector brings the trip lever to engage the semi notch, which is in the upper side of a window in the sear. In the other position, it engages the auto notch in the lower side. In the intermediate, “safe,” position, the  trip lever clears both notches and the weapon does not fire.

Note that automatic safeties, too, can be broken down as working on the trigger, the firing mechanism, and the sear, also. So safeties can also be Classified by Operation.

Safeties Classified by Operation

It is possible to classify safeties in the first place by their means of action:

  1. Trigger safeties
  2. Firing-mechanism (striker, hammer, firing pin) safeties
  3. Sear safeties
  4. Disconnecting safeties.

This is true, obviously, for both automatic and volitional safeties, and classifying them this way puts their mode of action forward as more important than their mode of engagement, which (applied/volitional or automatic) becomes a secondary trait.

One More Trait: Must the Firearm be Cocked?

It is only possible to engage many safeties when the weapon is cocked or ready to fire (presuming a chambered round). Familiar examples include the AR series rifles and the 1911 pistol and other Browning hammer designs. Other safeties engage regardless of the energy state of the striker or hammer, for example the AK, the Remington Model 8 (a Browning-designed trigger mechanism that was deeply influential on 20th and 21st Century firearms designers, including Garand, Kalashnikov and Stoner), and the RPD light machine gun.

Combination Safeties

While a weapon may have multiple safeties that do different things (or multiple modes that engage the same safety, as in the safety lever and grip safety of early Lugers), it’s possible for a single cunningly-designed safety to disable multiple points of the firing chain at once. For instance, the Lee-Enfield safety is a model of versatility: it locks the striker, locks the bolt closed (preventing the chambering of a round), and disconnects the striker from the sear. The M1911 or Browning High-Power safety locks the slide closed as well as locks

It’s also possible for a volitional safety to be combined with other functions. The most common example of this is the combined safety/selector switch of most modern assault rifles, like the M16 or AK-47.

To Sum Up

There are a great but finite number of ways to design safety features on modern firearms. Careful study of prior art allows today’s designer truly to stand on the shoulders of the giants in the field. John Browning left no memoir or technical book, nor did John Garand, John D. Pedersen, Gene Stoner; and the many memoirs of Mikhail Kalashnikov are disappointing to the technical reader. But each of these geniuses spoke to us in the art of his designs, and they are still available for us to study and to try to read what their art is trying to tell us.

We have not, in this limited post, attempted to discuss “best practices” or the pros and cons of any individual safety design. Very often, the designer will be limited by the customer’s instructions or specifications. (For example, the grip safety of the 1911, which 1970s and 80s custom smiths often pinned in engagement as a potential point of combat failure, was requested of John M. Browning by the US Cavalry. The other military branches didn’t feel such a need, but the horse soldiers did, and Browning first added it on his .38 caliber 1902 Military pursuant to a similar request). Thus, even as a designer, your safety design decisions may not be your own.

Notes and Sources

  • This post has been modified since it was first posted, to expand it.
  • This post will be added to The Best of WeaponsMan Gun Tech.

This post owes a great deal to the following work:

Allsop, DF, and Toomey, MA. Small Arms: General Design. London: Brassey’s, 1999.

Chapter 13 is an extensive review of trigger mechanisms, including safeties, and while their classification of safeties is different from ours, their explanations are clear and concise.

Thanks to the commenters who not only recommend this long out-of-print book, but also sent us a link to a bookstore that had it (it’s a copy withdrawn from a military library, as it turns out). This out-of-print work is less technical and deep, but considerably more modern, than Balleisen; its examples are primarily British.

 

8 thoughts on “A Taxonomy of Safeties

  1. Miles

    In reference to:
    6. Firing-pin immobilizers as in the Colt Series 70 and newer M1911s;

    Apologies sir. I believe you need to edit “70” to “80”.

    80 series has the firing pin block.

    1. Hognose Post author

      Crap, the Series 70 was the collet bushing, wasn’t it? Will fix, you’re quite right. Of course, there was an even earlier FP safety in 1930s Colt commercials, the Swartz safety. But it was dropped in the runup to the war. Kimber uses it now.

      I also think the article really needs illustrations.

      1. Miles

        Yes, that collet barrel bearing which seems that almost everyone (including me, but that was because I was replacing barrels with .mil NM barrels) replaced as soon as possible.

  2. Neil S.

    I would be fascinated to know if data exists for the number of accidents directly attributable to users ND’ing with weapons having only an automatic safety (i.e. Glock and clones thereof). My primary carry gun has been an M&P for several years now, and reholstering the weapon in an IWB holster has begun to make me nervous.

    1. Miles

      I can’t comment on specific numbers, but there have been enough for it to be a well known webmeme (did I just make up a word?) anyway.

      Take care to LOOK where you’re holstering your pistola to make sure there will be nothing in the way, like fingers, jacket pull strings, shirts, or…whatever and also perform proper PM on your holsters so you can trash them at the first sign of wear that would affect safety. Yes, that’s a pain in the wallet, but I would think less painful than that a pain in the body.

      Of course, the incentive to keep a ‘unique’ job has influenced the people I knew to be especially vigilant in this regard.

  3. Pathfinder

    Not to pick nits, but did some text get dropped at the end of the first paragraph under “Combination Safeties”.

    Another excellent article and another book I need to pick up.

    Thanks.

  4. AuricTech

    According to the folks at Sturm, Ruger & Co., that firm’s SR1911 (the Ruger version of the M1911) “features a titanium firing pin and heavy firing pin spring, which negates the need for a firing pin block.”

    Where would this feature fall within your taxonomy?

    1. Hognose Post author

      Several makers use the Ti pin and heavy spring as a drop safety. It works but is not fail-safe: if the spring fatigues, even the low-inertia lightweight pin can generate enough joules to make the primer happy. But it is intended as a safety feature as the Swartz or Series 80 firing pin locks are.

      The Walther P.38 physically locks the firing pin (which is why the safety is on the slide). The most common Beretta 92 versions actually have a section of the firing pin inside the safety, so that with the weapon on safe the pin is both locked and has a section that’s some 60º out of line and can’t transmit energy regardless.

      The SR1911’s titanium FP may be considered a weak form of automatic safety. Another weak automatic safety is, for instance, the half-cock notch on single action autos. Its only real purpose is to catch the hammer in case of a slip while cocking. It is the only safety on the Soviet TT-30 and -33 service pistols. We didn’t mention that because as a safety it’s rather lame.

Comments are closed.