On Reliability of Drum Magazines

Puma PPS50 drum byBlack Dog Machine keeps each cartirdge separate and not under pressure.

Drum magazines have long had a bad reputation. “We found many Angolan and Cuban soldiers dead, with jammed RPK drums in their rifles” said a South African veteran. “PPSh drums had to be down-loaded by a few rounds, usually had to be fitted to individual submachine guns, and jammed more often than box magazines” wrote Soviet veterans of WW2. And yet drums persist in weapons large and small — have you ever wondered why?

Puma PPS50 drum byBlack Dog Machine keeps each cartirdge separate and not under pressure.
Puma PPS50 drum by Black Dog Machine keeps each cartridge separate and not under pressure.
MD Arms 20rd drum for 12ga Saiga has same featureL it may be left loaded long-term without defornation of the ammunition from spring pressure.
MD Arms 20rd drum for 12ga Saiga has same feature. It may be left loaded long-term without deformation of the ammunition from spring pressure.

Drums actually predate semi and full auto firearms. Several designs, gravity fed or mechanical, were in use with the Gatling guns. The early pan designed for the .303 Lewis light machine gun copied the mechanical arrangements of the Gatling. A ratchet in the receiver activated the magazine rotation with each stroke of the piston. That avoided dependance on the rather unreliable clockwork springs which were the other typical motive power for drums. Clockwork rotary magazines are almost as old: the Krag-Jorgensen rifle used one, and so had Mannlicher-Schönauer. Ruger 10-22 and Steyr SSG69 are direct descendants of the latter design. Its major advantage is individual handling of cartridges, which protects them from deformation. With shotgun magazines, such as the MD Arms drum, the freedom from deformation is an important feature, as plastic hulls can go out of round in longer box magazines. It’s equally important for the 22LR cartridges which are relatively delicate: only the few rounds inside the feed tower are under spring pressure, the rest are safe between the pawls of the drum ratchet.

The “snail drum”was the first widely used high-capacity clockwork-driven magazine, first used with Luger pistol and later with MP18 submachine gun. A cumbersome device of imperfect reliability, it was replaced with stick magazines in the successor MP28. The recent MGW 90-round drum follows that concept. The German machine guns of the 1930s improved reliability and feed rate by using two springs, giving the magazines a distinctive double-drum (doppeltrommel) look. MG15 aircraft gun ran at over 1000rpm and the drum kept up. That dual-spring approach is still used today with Beta and Armatac dual drums.

PPSh drum nominally held 71 rounds but loading 65 helped to avoid jams.
PPSh drum nominally held 71 rounds but loading 65 helped to avoid jams.
Chinese 75rd RPD drum improved on the Russian version by using multiple pawls to move the ammunition.
Chinese 75rd RPD drum improved on the Russian version by using multiple pawls to move the ammunition.

Thompson, Suomi K31, PPD and PPSh drums all used a floating follower set inside a spiral track. Thompson magazines (and later Chinese RPK drums) separated cartridges into clusters to reduce friction. The others, along with the derivative Russian RPK drums, did not. With the limited power spring, friction became an issue. With the Thompson drum, better reliability was bought at the cost of not having all cartridges under pressure and rattling against each other.

Better spring metallurgy and longer feed towers (to make feed lip position repeatable) make modern drums more reliable. Better casing materials and designs also make them very durable: Armatac’s designer Mike Snow demonstrates how tough his creations are by forcefully bouncing the loaded drum several time off a concrete pad, then firing off the entire 150-round load with no stoppages. While bulkier than individual 30-round box magazines, drums are more space-efficient when heavy volume of fire is needed. Compared to belts, they allow for lighter, simpler feed mechanisms on the guns. Drums also keep out dirt better than belts do. This is why Ultimax100 and MG36 light machine guns both use drums instead of belts.

Heavy-barrel FAL by DSA with 100rd Beta drum
Heavy-barrel FAL by DSA with 100rd Beta drum
Anderson AM15 carbine with 150rd Armatac drum
Anderson AM15 carbine with 150rd Armatac drum

In civilian use with semi-automatic rifles and shotguns, drums are best suited for defending fixed positions, such as homes. Where light weight and mobility are less important than being able to turn back a determined assault, drums have a place in our ready kits. In such cases, heavy barrels are advisable as well. Coming back to the bad reputation of drums — the two examples mentioned were both mediocre designs produced to indifferent quality and usually badly maintained. Suomi drums, while internally similar to the PPSh design, were made to much higher tolerances and were more reliable than the quad stack box magazines also fielded by Finns. In case of the Cuban and Angolan troops, even such reliable stalwarts as the AK47 feel to poor maintenance and lousy training. Judging modern drum designs by those examples is not very useful.

About the Author:

Oleg Volk

Oleg Volk is a creative director working mainly in firearms advertising. A great fan of America and the right to bear arms, he uses his photography to support the right of every individual to self-determination and independence. To that end, he is also a big fan of firearms.
The Mission of Cheaper Than Dirt!'s blog, The Shooter's Log, is to provide information—not opinions—to our customers and the shooting community. We want you, our readers, to be able to make informed decisions. The information provided here does not represent the views of Cheaper Than Dirt!

Comments (14)

  1. I have an I.O. Inc AK47… Have it 3 years, when I bump fire with that drum it jams after about 20-30 rds… I want another AK,, Whats the best kind to get????

  2. Drums just allow me to burn through ammo faster. That is good when you need lots of lead, but bad at the range… because it gets expensive real quick.

  3. @Northman , The reported failure was a stove pipe jam and the robbers thumb was shot so he couldn’t fix it. Source: National Geographic special.

  4. I have a pair of Korean made Chinese drum magazines for my AK. At first I was worried that they may not work as well as I’d hoped, but so far they’ve been problem free at the range.

  5. Actually, I believe that the one psychos weapon DID eventually jam. I believe that he is the one that shot and killed himself with a pistol as they closed in. Could be mistaken but that is what I remember hearing. But, his weapon certainly worked for a good while and he may have just run out of ammo.

  6. Seems to me, the two psychos who robbed a bank and went on a shooting spree in California had drum magazines in their AKs. They certainly didn’t have any feed issues, guns ran flawlessly.

  7. Well fellers , the only mag`s I have found , that work in my battel rifle is the 20 rounder`s , without a hick~up here and there . I can`t stand a damn hick~up when I`m rapid firing my rifle . I wanta KNOW” , I can depend on my rifle to fire EVERYTIME , if I get into a fire fight Peiord . My 20 mag`s do just that , so I s%$T can`ed all the 30 rounders I`ve ever bought and loaded my gear up with 40 , 20 round mag`s , and finely quite poring money down a rat hole , in order , to come up with some kinda large cap. mag`s. that work`s Without Fail . I`ve spend a lota damn money on High Cap mag`s and finely said too hell with it . I belive in FLAWLESS” working ,High Cap mag`s , like I belive in our Government . I have ZERO” , Trust in Both . I tell ya this though , Carrying 800 ~ .223 round`s with 40 mag`s in your gear , is not fun , but I figuer I can hold off a determined fire fight , for a while , before I go down , Esp: if I`ve got a buncha my buddy`s with as much ammo , hunkered down with me . Some of us may catch one between the eyes before it all said and done , but That`s part of War” Boy`s and Girls , and you except that posible fact , if you go to battel . I was told though , once as a Marine” , I was Not Aloud To Die Without Permission ! Maybe that`s why I`m still alive today , My Sargent never did” , give me that permission .

  8. Good posting. I love the fact you mentioned that drums are better for static defense rather than moblie ops. However, a drum as a “starter” mag, may be very useful in a mobile op if you’re expecting trouble, with sticks backing it up. However, a larger dump pouch or several small ones are also needed. Lets face it, as civilians, we don’t wanna drop our mags on the move. We don’t have taxpayer money replacing them.

  9. The question is not how do they run when clean. The question is how do they run after being reloaded in field conditions for a year or two.

  10. I own 6 drums. 3 for my saiga 12, 1 beta
    for 556, and 2 22lr for my ar platform. I
    love the ability to keep shooting while
    others have to stop and reload! All
    of my drums have proved reliable! And
    I shoot that beta can mag on an ar
    with a slide stock!

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