Drop Safety Question

[Balood128]

Hi

I am not a gun owner but I am a fan of Gun Jesus on Youtube. I was just wondering why they did not have a simple front notch as a drop safety on smg's such as a Sten. There is of course a notch at the back for the safety but why not have the same thing at the front. I have done a rough drawing. I am sure there is a simple answer as to why no SMG's have this.

[4V50 Gary]

Firing pin blocks were rare back in the '40s. The Walther P-38 was one of the few to have it. The Swiss had a grip-safety on their version of the P-08 Pistole, so the concepts of some form of safety was not new.

Why not implement the safety features? Remember wartime expediency demanded cheap, easy made SMGs and with the fewer the parts, the cheaper and easier it is to fabricate. Even the original Uzi didn't have a grip safety until some soldier dropped a non-grip safety one and it sprayed all over the place. Whether Soviet, German or British, all major powers were concerned with arming their soldiers quickly. They relied on training to make the soldier safe and effective with it (though in wartime training could really suffer).

[44 AMP]

I am sure there is a simple answer as to why no SMG's have this.

The simple answer is that it serves no purpose.

Although mechanically very simple, open bolt SMGs are widely misunderstood by people who have not been trained on them.

I have personal experience with the US Thompson, and M3/M3A1 "greasegun", the British Sten and the German MP38/MP40, (which people incorrectly call a "Schmeisser") as well as several post WWII designs including the Mac 10 and the Uzi.

When you say "front notch" I am assuming you are referring to a front version of the inverted "L" shaped notch in the receiver tube that the Sten and the MP40 have at the rear?

Such a notch would allow the bolt to be locked in its forward position, but would not make the gun significantly safer in use though it would technically increase the drop safety of the gun very slightly, it also introduce a slight increase in cost and complexity of manufacture, bue more importantly, could be a complicating factor getting the gun into action in combat.

As mentioned, "drop safety" was not a high priority of gun design during those years, and the firing pin blocks used in handguns these days simply cannot be applied to the open bolt fixed firing pin SMGs.

The only time these guns have a round in the chamber is when it is being fired. Locking the bolt forward on an empty chamber doesn't do much to increase the safety, except in one very, VERY rare situation.

And that situation is, loaded magazine in the gun, bolt forward (chamber empty -the only way this can be done) IF the gun is dropped (or shaken violently) in just such a manner that the bolt comes back enough to pick up a round from the magazine, BUT NOT ENOUGH to engage the sear and hold the bolt back (a very small distance further) then the gun will fire when the bolt goes back forward. This is a very, very small possibility, and while possible, it was generally not considered a significant risk by the people designing the SMG, and most designs don't have anything that specifically prevents that very rare occurrence.

There is one I know of, that does, and that is the US M3/M3A1. And the Greasegun doesn't use a notch in the receiver tube or bolt handle, at all.

Generally speaking, open bolt SMGs are carried "on safe" with the bolt locked back. There are two common ways the bolt is locked back "on safe". One is physically locking the bolt from moving usually done by "locking" the bolt handle into a notch where it cannot move until the shooter moves the handle out of the notch.

The other way is to use the sear of the gun, which holds the bolt back until the trigger is pulled. These guns use a safety (switch or grip safety or both) which prevents the trigger from being pulled.

The Tommygun, the Uzi and the Mac 10 guns use that kind of system. The STEN, and the MP40 physically lock the bolt handle in a notch so pulling the trigger does nothing. The Greaseguns also physically lock the bolt from moving, but use a rather ingenious method (since there is no bolt handle) locking the bolt from moving using a tab on the ejection port cover. And, the designers were smart enough to add a second hole in the bolt so that, with the cover closed, the bolt is locked in either the forward or rearward position.

Additionally, the idea of an SMG going off when dropped and "running away" firing until it runs out of ammo is pretty much movie BS, UNLESS the gun is broken (or specially rigged to do that).

IF the gun is not broken, full auto guns will only run full auto when the trigger is pulled and HELD TO THE REAR. If the trigger is not being held to the rear, the gun and something jars it enough to let the bolt go forward, it will fire ONE round, and then the bolt will be caught and held to the rear, by the gun's sear system, unless the gun is broken and that system is not functioning.

Open bolt guns work almost the exact opposite of regular guns, and require both training and due diligence on the part of the user to work safely. I have personal knowledge of one accidental discharges (actually a negligent discharge) due to a new user not being familiar enough with an Uzi.

This happened at a US nuclear facitity!! The Tactical Response Team portion of the guard force, which was equipped with M16s issued some Uzi's to a portion of the force, (shorter and handier inside buildings) and while they were trained, ONE guy wasn't trained ENOUGH!

According to the wording of the accident report he was "giving an informal class" on the gun (aka "showing it off") in the facility lunchroom (), at the end of which, he "returned the gun to service" by doing exactly what he did with his M16, bolt back, inserting a loaded magazine, and releasing the bolt to go forward. At which point, naturally the Uzi fired!

ONE round, into the lunchroom ceiling! (apparently not only did he not remember that letting the bolt go forward to chamber a round also fired the gun, but pulling the Uzi's trigger (necessary to allow the bolt to go forward) didn't tip him off!)

Those of us who actually understand how the Uzi works found the "officialese" of the accident report amusing, in that it described the Uzi as "a select fire, magazine fed weapon with a manual safety and a grip safety that positively preclude the possibility of an accidental discharge...see note A..."

Note A was not attached to the copy of the report I read but we all figured that it had to say something like "positively preclude the possibility of an accidental discharge, until you give it to an idiot!"


Hope this "simple" explanation helps your understanding and answers your question about why SMGs don't have another "safety notch".

Feel free to ask about any other questions you have. We're here to answer to the best of our ability and experience.

[Balood128]

Thank you for your excellent reply. The question was an itch I had to scratch.

[RickB]

You definitely do not want to lower the bolt on an open-bolt SMG to make it "safer".
With the bolt locked back, in ready condition, the firing pin is an inch from a chambered round, and seems like a safe place.
I was having a bit of a debate about the manual of arms for open bolt guns, my contention being that the loading process involves first locking the bolt back, so you are certain it is actually locked back, before inserting the magazine; you don't want to fumble the bolt with a magazine in the well.
Some pooh-poohed the risk, but if you have to perform both actions to load the gun, retracting the bolt and inserting a magazine, it's certainly safer to do them in that order.

[44 AMP]

The proper manual of arms to ready an open bolt gun for use is to retract the bolt to its normal locked open position, apply the safety (if any) and THEN insert the ammunition.

There are some guns that will allow you to insert a loaded magazine with the bolt forward on an empty chamber, and there are some that will not.

Unless the maker specifically instructs otherwise, it is open bolt (locked, if possible), then insert ammo. This order works will all SMGs I know of, and all open bolt belt fed machine guns as well.

some designs will not allow inserting a magazine with the bolt forward (you cannot remove or insert a tommy gun drum with the bolt forward) some others will allow you to put the ammo in, but then not allow the bolt to come back properly. I have personal experience with this on the M73/73A1.M219 machine gun. (coax gun for M60 tank throught the 70s)