100 rounds of Firepower for the Glock
By Frank Iannamico

Although there are a number of “YouTube” videos featuring a 9mm full-auto Glock 18 dumping a 100-round Beta-C dual-drum magazine, finding a 100-round Beta Mag for a Glock (that works) has been a challenge. All of those Beta C Mags previously demonstrated on Glock pistols were individual concoctions of 33-round Glock magazines, and 9mm Beta C Mags originally designed for other applications. Although there were a few entities advertising drums for the Glock, they were either not available, or not in production. Several attempts to locate a working drum were fruitless, although two “home-workshop” drums “guaranteed to work” were purchased; one a converted Beta C Mag, and the other a converted Suomi drum: neither one worked reliably.

Turning to the Beta Company as a possible source, it was a surprise to hear that they were in fact planning to design and market a Beta C Magazine for the Glock. However they had just introduced the Uzi Beta Mag and had not yet started on the project, which they estimated would not be available for quite some time.

Finally, nearly a year after speaking with the manager at Beta, the day arrived; a genuine factory-made Beta C Magazine for the Glock 18. With a full-auto cyclic rate of over 1,000 rounds per minute the 21.9 ounce Glock pistol can be a challenge to control. Loaded with one hundred 115-grain 9mm cartridges, the Beta C Mag adds 5.1 pounds to the pistol; the added weight somewhat enhances the Glock’s controllability, which of course diminishes somewhat as the drum is emptied. The unloaded Beta C Mag weighs 2.2 pounds.

Although emptying a Beta C Mag is an indescribable rush, loading one is not. Despite the factory supplied loading tool, loading 100 rounds into the drums through the single feed box magazine is a time-consuming task. Using an UpLULA loader, in place of the one supplied by Beta, made the job a little easier. When loading, the cartridges are inserted on top of the spacer rounds, through the double-stack, single-feed magazine and into the drums. The cartridge column splits at the juncture of the feed clip and the housing to distribute the ammunition evenly into the drums in two concentric rows. The factory loading tool provided with the Glock drum is a simple design. Some loaders, like those designed for the all of the 9mm Beta double-stack Beta C Mags, are easier to use, but a problem is sometimes encountered with the propensity of the 9mm rounds to reverse direction after they are placed in the loader, the problem is not usually noticeable until it jams the internal mechanism and prevents any more rounds to be loaded. Clearing the jam required unloading the drum; the optional clear plastic back panels of the drum are useful for finding an errant cartridge. However, after a few loadings one could easily acquire a “knack” for loading the drum without the aforementioned problem occurring.

The basic Beta C Mag magazine was invented by Leroy James “Jim” Sullivan, a noted firearms designer who was part of the original AR-15 M-16 design team at Armalite in the 1950s with Eugene Stoner and Arthur Miller. Mr. Sullivan’s inspiration for the “dual drum” magazine originated from the German 75-round saddle drum magazine designed for the MG15 and MG34. Mr. Sullivan’s original drum idea was for an assault rifle he was designing for Beretta. After the Beretta project was shelved, Mr. Sullivan decided to redesign his drum magazine for the M16 rifle. The original design was to be an expendable package for military applications, which would be discarded after use. One of the problems encountered in the design was having the cartridges feed fast enough to keep up with the fast-cycling bolt, the spring pressure required to push 100 rounds vertically through a magazine placed too much drag on the bolt, which resulted in jamming and stoppages. The drum(s) had to feed the cartridges to the weapon as fast as a 30-round magazine.

The solution to the feeding problem without overly increasing spring pressure was to design an “accelerator” into the drum. The accelerator consists of two separate circular rings of ammunition moving together; after the cartridges get to the end of the circle they meet at a cam blade that merges the cartridges into a vertical column. As they are pushed together, the speed of the cartridge stack is increased, changing from a double column to a single column. That doubles the speed and reduces the force of the column of cartridges in half. The rounds feed up through the magazine and into the weapon.

The production Beta C-Mag is a compact twin-drum magazine design that accepts up to 100 rounds of ammunition. It consists of two main components: the twin-drum storage housing and an interchangeable single “tower” in the shape of a weapon specific box-type magazine assembly. The drums are spring driven and feed alternately from either side to produce a constant 100-round supply of ammunition. With the drums feeding from alternating sides, the magazine does not become unbalanced as it unloads during firing. Before loading and after firing, the magazine that fits in the host weapon is filled with a string of dummy spacer “rounds” that push the live rounds up through the feed magazine. The upper half of the top spacer round is tapered to allow the weapon bolt to close after the last round is fired. The number of spacer rounds depends on the length of the magazine adapted for the individual weapon. Liberal doses of powdered graphite placed on the top spacer rounds before loading help reduce the friction inside the magazine; the manufacturer warns that no oil or solvents should ever be used to lubricate or clean the magazine. Complete instructions for the maintenance of the magazine are included with each magazine. The first 5.56mm 100-round drum was placed into production by the Beta Company during 1987.

The dimensions of the 9mm drum are 11.17 x 4.72 x 1.57-inches, empty weight is 2.2 pounds. Main components are made of filled thermoplastic material. Other components are made of non-corrosive steel, alloy materials.

The Glock 18 Machine Pistol

The Glock 18 is a select-fire variant of the Glock 17, developed at the request of the Austrian counter-terrorist unit Einsatzkommando Cobra. At first glance the Glock 18 looks much like a semiautomatic Glock 17, except for its rotating lever-type fire-control selector switch, located on the left rear side of the slide. The mode of fire positions are marked with indented “dots.” One dot at the upper position is for semiautomatic fire, the lower position, full-automatic, is marked with two dots. The overall length of the Glock 18 is 7.28-inches, barrel length is 4.49-inches; unloaded weight is 21.9 ounces. The Glock 18 is typically issued with a 33-round capacity magazine, although other magazines from the 9mm Glock series will fit and function.

In an attempt to make the Glock 18 more manageable, a new version was introduced, known as the Glock 18C. To help control muzzle rise it has a compensator cut into the forward portion of the slide. The keyhole shaped opening provides an area to allow the four, progressively larger (from back to front) compensator slots machined in the barrel to vent the propellant gases upwards, to push the barrel down, affording more control during full-auto fire. Most major components of the Model 18 are not interchangeable with other Glock models.

The Glock 18 is basically a 9mm short recoil-operated locked breech select-fire pistol that uses a modified Browning cam-lock system adapted from the Hi-Power pistol. The firearm's locking mechanism utilizes a link-less, vertically tilting barrel with a rectangular breech that locks in the slide. During the recoil stroke, the barrel moves rearward initially locked together with the slide approximately 3mm (0.12in) until the bullet leaves the barrel and chamber pressure drops to a safe level. A ramped lug extension at the base of the barrel then interacts with a tapered locking block integrated into the frame, forcing the barrel down and unlocking it from the slide. This camming action terminates the barrel's movement while the slide continues back under recoil, extracting and ejecting the spent cartridge casing.

In place of a conventional hammer, the Glock design uses a striker. The striker firing mechanism has a spring-loaded firing pin that is cocked in two stages, powered by the firing pin spring. When the pistol is charged, the firing pin is in the half-cock position. As the trigger is pulled, the striker becomes fully cocked. At the end of its travel, the trigger bar is tilted downward by the disconnector, releasing the striker to fire the cartridge. The disconnector resets the trigger bar so that the striker will be captured in half-cock at the end of the firing cycle. The pre-set trigger mechanism is referred to as the "Safe Action" trigger by the manufacturer.

The Beta Company currently offers their Beta-C magazines in several calibers for a number of applications including:
  • 9mm: HK MP5, Colt 9mm M16, Uzi, Glock
  • 5.56x45mm NATO: the M16/M4/AR-15 family, M249, G36, HK 33/53, Ruger Mini-14, SIG SG550, 551, Steyr AUG, SA 80, HK 416, FN SCAR.
  • 7.62x51mm: M1A/M14, HK 91/G3, FN FAL.
Currently under development are Beta C Mags for the 7.62x39mm AK weapons and 6.8 SPC rifles.

The Beta C magazines are available with or without the accessory kit. The kit includes a fitted pouch, loading tool, dust-cap, and graphite lube. Most rear covers are available in clear or black. Estimated service life of the Beta Mag is 60,000 rounds; all Beta C Mags have lifetime warranty support. A fully loaded Beta C Mag can be stored indefinitely with no loss in performance. The Beta Mag requires no maintenance other than cleaning and powdered graphite lubrication.

Most caliber-specific Beta C Mags can be used in other applications by simply switching out the feed tower magazine and the appropriate number of dummy rounds for that application. Unfortunately, as of this writing, the feed towers for the Glock and Uzi are not available separately.

Sites of Interest:

Glock USA


Beta Company
Tucker GA
(800) 669 2382

LULA magazine loading tools

This article first appeared in Small Arms Review SAW (August 2012)
and was posted online on June 29, 2012


Comments have not been generated for this article.