Bren 100-round Drum

The Bren light machine gun is far from a forgotten weapons, but some of the accessory bits that were used with it are pretty rare today. The 100-round drum magazine issued for anti-aircraft use are one such item.

Bren gun with 100-round drum magazine
Bren gun with 100-round drum magazine

You might be wondering how you are supposed to use the sights with that drum in place – well, you don’t. The drums were intended for antiaircraft use, and thus the guns using them would have taller AA spider sights installed. Some were also uned on armored vehicles, but this was more of an afterthought and not the original intent. The drum requires an additional mounting bracket to hold the front end in place, while the rear of the drum has a set of feed lips like a regular box magazine and snaps into the magazine catch. As you can see below, the drum adapter does not preclude the use of standard box magazines.

Bren with drum adapter and box magazine in place
Bren with drum adapter and box magazine in place

We have a few more photos of one of these drum magazines and its setup on the gun (click here to download them all at high resolution):


Edit to add: Oleg Volk has a great photos of one of these drums as well, including one of the piece disassembled:

Bren mags, by Oleg Volk
Bren mags, by Oleg Volk
Bren drum mag, by Oleg Volk
Bren drum mag, by Oleg Volk
Bren drum disassembled, by Oleg Volk
Bren drum disassembled, by Oleg Volk


  1. Might these also be intended for use in the sustained fire role on the Tripod? Because 30 rounds a box magazine does not seem like much sustained fire.

    • That’s the big edge the Germans had in their MG34 and MG42. Belt feed is innately superior for the sustained fire role. With the Bren, you had to be quick at changing mags. The top-mounted magazine helped with that, though.

      • Belt feed is one thing, but the MG34 and MG42 were both air-cooled weapons, obviously, and that, coupled with very high rates of fire, means frequent barrel changes. The MG42 was supposed to have its barrel changed every 250 rounds! Not exactly conducive to true sustained fire. Good weapons, both, but for sustained fire the old water-cooled designs were still the masters.

        • Well, with the MG42 barrel change procedure, and burst fire, the barrel change really isn’t that different from a normal firing break, or a belt reload.

  2. I’m not sure they really would be because they obscure the sights. It would have been pretty cool though, Bren’s probably could have replaced quite a few Vickers MGs.

  3. Well the rear sight dovetail looks to be the same as the one on a Vickers gun. Maybe it was intended that the dial sight for the Vickers was to be used on the BREN in the sustained fire role. Does anyone know if a Vickers dial sight fits in the dovetail on a BREN?

    • ~Big Al-
      The pictured BREN is a MkI, where the more common MkII and later series did not have that complicated rear sight.

      The reasoning I was given as to “it blocks the sights” was “the drum will be loaded with tracer or incendiary, adjust fire as needed”.

      • Meplat,
        Thank you, I am familiar with the various marks of BREN. The reason I thought the Vickers dial sight might be used in the sustained fire role in conjunction with the drums is that the sighting tube of the dial sight is higher than the primary rear sight of the BREN and does not require a front sight to use. However, with a little hunting around the interwebs, I came across a reference to a Sight, Fixed Line, BREN .303 MG. After further digging, I found a pic on the forum in the following link (post #158, third photo):

        The gun depicted has two dovetails. Even though the sight is mounted in the forward dovetail in the photo, both dovetails (and the one on the gun pictured here) look to be similar if not the same. The fact that that this gun has only one dovetail tells me the design was simplified over the years as it was realized that you don’t need two dovetails of the same dimensions for mounting the sights.
        The defense rests, your Honor.;)

  4. Disassembly photo – In the main section of the drum assembly is the runner for the cartridges a spiral? If so it must have taken an age to reload!

    • Well, that is typical of drum mags… both the spiral and the ages of reloading time.
      To my understanding, it’s why they aren’t in use since box mags were made practical.

  5. In the 50’s I was a Bren 1 and 2 in a regimental team and competitions. We fired literally hundreds of rounds which had to count, and we were good. All under strict rules as well as fire and movement exercises. Our effective maximum range was 600 yards. Many videos that I watch today have turned the stripping and re-assembly into a circus act of little value. What do they achieve? No better than changing a bicycle tyre.

    Why strip the gun? Well the obvious is to clean, oil and check working order. The armourer is best for this job but the operator is quite able and under conditions of rest has no need to rush about getting nowhere.

    Under simulated fire conditions what do you do? Keep you head down. Stay prone.
    1. out of ammo. Not as daft as you might think.
    2. barrel too hot.Unlikely.
    3. gas regulator wrongly set.
    4. Extractor clip stuck.
    5. Bent round.
    5. Magazine jam due to overload, dirt or weak spring.
    6 Little else in time allowed. 50 seconds to move from prone, run 100 yards, back to prone and fire 18 rounds. Single shots were most accurate.
    Stoppage event.
    The first operation was to clear the gun and change mags. The gun would have remained cocked if out of ammo which is easy to recognise. No 1 would give the order,roll away to the right and No 2 would have the new mag on in seconds and empty it. No 1 would roll back on he next mag change, or stay as 2.Carrying in turn
    Change barrels is unusual as each is zeroed on the foresight for a particular operator but is performed using the same method and as fast as mag change. 5 tracer doesn’t help cooling and they can ignite the targets.
    Still not working? well you haven’t long to live let alone fart about stripping down waving your head about in the line of fire. Push out the stock lock pin with a round. Pull the stock back 2/3 way and jerk the cocking handle to release the piston assembly. Check for breakages, grit and the extractor spring. Wipe it down and put it back. There is no point in taking anything else apart. You could be in the desert or a trench. Hands will be shaking by now.
    Leave the trigger group alone as you would be unlikely to be able to re-assemble; as a must check the sear and bent. You will not have the parts.
    Still not firing?
    At this point grab the barrels and RUN.

  6. I do agree with all the ideas you have offered to your post.
    They are very convincing and can certainly work. Nonetheless, the posts are very brief for novices.
    May just you please extend them a bit from next time?

    Thank you for the post.

  7. British: Let’s take this exclusively light MG and turn it into something else that it is not intended for.
    Universal Machinge gun 34: Let me introduce myself.

    But then they Luftwaffe just used other MGs exclusively as defensive armament.. oh well

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