Open bolt gun question

No, the bolt would most likely be at the forward position. Emptying the mag would be "bang, bang, bang, thunk," the "thunk" being the bolt slamming forward on an empty chamber and would be an indicator to the user that the gun is empty.

So, if you ran it dry, you'd need to pull back the bolt and swap mags.

The bolt is only held back by the firing sear. Unless you were quick enough to notice the mag was empty and let go of the trigger, then no, it will run forward trying to fire the next cartridge in line. So, you have to pop in a new mag AND run the bolt handle.

Like most guns, its usually best to not let it run totally dry, then you won't run into this issue. Reload at your convenience, under cover.

What if you didn't hold down the trigger on the last shot, or you had the gun set for single? Then the bolt would drop, fire the round, and be driven back and held back and open by the trigger mechanism, correct?

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If the bolt is locked to the rear, it is locked to the rear. It's cocked and ready to go.

The only time an open bolt gun loads the chamber is a split second before it fires.

So, if the bolt is locked to the rear and the trigger is pulled, the bolt will slam forward. If there is a loaded mag in place, it will strip, chamber, and fire that round, then will be blown to the rear.

If there's no ammo in place, the bolt slams forward where it stays.

"...quick enough to notice..." That's why the third last round should be a trace. Tells you to change mags.

That's why the third last round should be a trace. Tells you to change mags.

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"Okay, Karl, wait for the tracer round to fly over your head and then let loose with the MG-42. I'll sit here and laugh my Nazi behind off."

Isn't it different with a Thompson?

Thompsons are open bolt.

Oh, boy, a lot of confusion here.

First, both the STEN and the Thompson SMG fire from an open bolt in both semi and full auto modes.

The STEN has no empty magazine hold open. If in the full auto mode ("A" pushed in), when the last round is fired the bolt will close on an empty chamber and must be recocked to fire after replacing the magzine. (Normal drill is to cock the bolt first, so inserting a full magazine is easier.)

If the STEN is on semi-auto ("R" pushed in), the bolt will stay back after each shot until the trigger is pulled, but unless the shooter knows the magazine is empty (not easy), he will probably pull the trigger and the bolt will close. So the same drill applies as for auto fire.

The U.S. M3 and M3A1 have no bolt hold open on an empty magazine and are full auto only. The comments above on the STEN in full auto apply to the M3/M3A1 also.

The Thompson M1921 and M1928 have empty magazine hold open on stick magazines but not on the drums. The M1 and M1A1 have bolt hold open but will accept only the stick magazines. The original TSMG mags were th 20 round stick and and 100 round drum (XX and C) magazines; the military asked for the 30 round stick and the 50 round drum (XXX and L) magazines. In case you didn't notice, the magazine designations are the Roman numbers for the capacity.

The idea of using a tracer to signal an empty mag is fine except that tracers were almost never available in the pistol calibers. Generally, they were issued only to pilots and a few others for signalling or training. The FBI used tracers in TSMG's for night firing demos for the movies, but they were almost unknown in the military.

Jim

When I was a kid, the local sheriff had an H&R Reising WWII subgun that came with .45ACP tracers packed in the carrying case. (Or at least the tracers were there when I shot the weapon)

Just make sure when you go to make the gun safe, you pull the mag FIRST, or the next few moments will be exciting moments.

Just make sure when you go to make the gun safe, you pull the mag FIRST, or the next few moments will be exciting moments.

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Isn't that the way you do it with any gun? ie pull the mag, then ensure the chamber is clear.

The difference with an open bolt design is that after pulling the mag, you don't really have to retract the bolt to inspect the chabmer because the bolt is either already locked back, with an empty chamber, or it is forward, on an empty chamber. But for safety's sake, check anyway.

Is it true, on a Thompson, by the way, that the bolt has to be cocked prior to loading a drum magazine? Will it simply not come back?

Just make sure when you go to make the gun safe, you pull the mag FIRST, or the next few moments will be exciting moments.

PULL OPERATING BOLT BACK FIRST TO VERIFY EMPTY CHAMBER!

I have several accidental discharges after a mag dump and pulling the mag only to find that a bullet was jammed and it discharged downrange.

Kenneth Lew

Hi, Hatchett,

Yes, on the Model 1921, Model 1927* and Model 1928, the bolt has to be retracted before inserting the drum magazine. Unlike the stick mags, which are inserted from the bottom, the drums slip in from the side. The drums have a "U" cutout for the bolt and that is where the cartridge is. When inserting the drum the uncut part can't get past the bolt, so it has to be retracted.

The drum has a support "shelf" and that is what goes into the sideways slot in the trigger group. The M1 and M1A1 don't have that slot or the part of the magazine release that fits into the drum.

*The Model 1927 was the semi-auto version; unlike the modern Model 1927A1, it fires from an open bolt and is semi-auto only because the disconnector is always engaged and there is no selector.

Jim

you pull the mag FIRST

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I only have one open bolt SMG and I always pull the bolt back before removing the magazine. I like to be looking into the chamber as the magazine is removed. It also is an easy way to tell if it stopped shooting because the magazine is empty or the round in the chamber didn't go off.

My point with pulling the mag first was mainly aimed at those who would "decock" a loaded open bolt gun, rather than "unload" it. Also, due to the majority of people being unfamiliar with the open bolt guns and thinking its OK to drop the bolt, even on a loaded mag, thinking it will just chamber the round and not fire it. I've had this happen a couple of times, even with people who should know better and even after I warned them. Old habits I guess. I remove the mag before doing anything as it removes the source of the problem. I then pull the bolt back and check the chamber and then lower it to show its safe.(open bolt guns are shown "safe" with the bolt closed, at least around here and with those I shoot with) To load, you insert the mag first, then cock it, especially if the person shooting it is unfamiliar with it, otherwise, you are putting a loaded mag into a "cocked and ready" gun that will fire. Again, to those who are unfamiliar with them, they look safe(r), even with a mag in the gun, when the bolt is open, like a closed bolt gun or a semi auto. Open bolt guns can be hairy sometimes, especially if you are unfamiliar with them. The bolt does not need to be locked back for the gun to fire and only needs to go back far enough to strip a round and then go back forward. Some MAC's, especially the M11/9's with the small charging handle, can be hairy if your hands are sweaty and you try to pull back on the knob, as it can easily slip. I know, its happened to me and the gun did fire. You also have to make sure that even with the bolt down on a loaded mag, the gun is not safe unless the safety is on(which locks the bolt) as it is possible for the gun to fire if dropped. Another issue(mostly with novice shooters but not always) with any SMG, regarless of type is, you have to keep that finger off or away from the trigger while loading or if the gun stops running. I know it sounds silly and like you would never do it, but if the bolt should go forward(main reason you load an open bolt with the bolt closed) and you were on the trigger knowingly or not, the gun is of and running, and thats not just once, but until you stop it. Hang fires, rare as they are these days can also be a problem. I've had a batch of Spanish SMG ammo from the 50's that had a few and if you think its empty because it stopped, you might be in for a suprise when it starts to run again if you are still on that trigger. Again, this is mostly directed to those who are novices, but you never know, I've seen some "trained combat vets" do some pretty silly things when they got one in their hands.

Good points, AK103K, except that with the TSMG and a drum mag*, the bolt will close on an empty magazine and there is no way to remove the magazine without cocking the gun.

Also, there are some open bolt guns that can't be loaded with a full mag unless the bolt is back, since the cartridge column does not have enough slack to compress with the bolt forward. Of course, the solution to this is not to fully load the magazine.

* I am referring to an original drum magazine. There were some made that had a "neck" from a stick magazine welded onto a drum. These didn't come apart and were loaded from the top like the stick mag, so they used the stick magazine catch, not the drum catch, and could be used on the M1 and M1A1.

Jim