In order to reduce overall length of a cartridge handweapon to its minimum, firearms designers adopted the idea of placing the magazine in the grip. This idea has great merit and is found in nearly every pistol and many pistol carbines. By eliminating the port where a drum or stick magazine resides in the receiver, the carbine takes advantage of this feature in two ways:
1. By setting the magazine in the grip, the operator can bring his two hands together, even in the dark, to reload the weapon. Once the magazine is drawn, it is naturally brought to the port or chute to be inserted into the weapon through a biometric called “Hand finds Hand”.
2. By setting the magazine in the rear grip, that grip used by the dominate hand, the overall length can be reduced by several inches as the barrel feed ramp area is close to the area of the rear grip. This is seen in the UZI carbine vs the M3 “Grease Gun” where the M3 weapon has a port or chute forward of the rear grip and the barrel must be much longer, either for velocity reasons or for legal reasons for civilian ownership. See Photos:
This does restrict the size of the magazine to what can fit comfortably within the male human hand. A long magazine like an AR-15 magazine could only be used if it were the grip itself, it is simply too long to fit within a grip compatible with the human hand. This would also eliminate the possibility of customization and reduce the robustness of the grip, as a individual grip can be welded, filled, ground, taped and generally made to fit the unique hand of the operator, but a series of magazines cannot.
Magazines themselves must also be robust. Given that they are being inserted and removed over and over, they are being carried on pouches on the hip and in combat, a delicate magazine simply becomes unreliable. Feed lips get dented, magazine bodies get crushed, springs fail, bottoms fall out or cartridges “stick” inside magazines that have lost their factory dimensions for whatever reason, causing the weapon to fail at the most critical time.
A huge amount of work has gone into magazine design, it is an art form in and of itself. If a existing reliable, robust design exists, it is far easier to modify an existing and known reliable weapon design than to attempt to “reinvent the wheel”. This is what I sought for my Ultimate Carbine, a high capacity, high reliability, maximum service magazine that could hold at least 35 rounds of 10mm.
After looking at fifty to seventy different designs, I finally settled on four that could accommodate the 10mm cartridge. All are strong known reliable designs and were small enough to fit within the human hand. They are:
1. The M3 Grease Gun Submachinegun magazine
2. The Thompson SubMachinegun Magazine
3. The Glock 20 pistol Magazine
4. The Russian PPS-43 Magazine
I stared by eliminating the Russian design because the amount of rework necessary to both get the magazine to feed 10mm as well as have it be retained in the chute. While an excellent and strong design, the magazine has a pronounced curve to accommodate the 7.62 x 25mm Russian cartridge, unnecessary in a straight-walled cartridge like the 10mm. Further it has a large steel latch at the back which would have to be ground off and a new retention mechanism designed, defeating the whole purpose of using a simple, existing design.
The second to fall was the Glock design, which would require a new body to get to the 30 to 35 round capacity I wanted with utter reliability. Though there are various “extended magazines” or extenders for stock Glock magazine bodies, many of them are either fragile plastic or have proven unreliable. Several swelled during testing, making it difficult to insert them when full.
The two other designs (the M3 and the Thompson) would fit the cartridge perfectly (indeed the Thompson factory had once made a magazine specifically for the 10mm out of their standard 45 ACP magazines, but the project was abandoned after only 275 Thompson rifles were made). Both are of completely different designs, which allowed me to easily choose between them. The Thompson magazine has a rail on the back for guiding the magazine into the chute and thus its overall length is slightly longer than the M3 magazine. Further, its double feed design is somewhat less reliable and much more difficult to “tune” than the single feed design of the M3, which presents its cartridges in the same manner each time as the bolt goes back rather than the Thompson magazine which alternates feeding cartridges to the feed ramp left to right. Though the Thompson is slightly lighter and shorter than the M3 magazine, it is also less robust, with somewhat delicate feed lips unlike the M3 magazine which has feed lips which are made of double thick steel. Also, the single feed design meant that as I adjusted the lips for perfect feeding for the narrower 10mm cartridge, each adjustment would effect every cartridge, instead of the Thompson magazine in which I would have to adjust each sides feed lip independently. The longer overall length of the M3, if it became a problem, could be easily changed without damaging the critical feed area merely by shortening the magazine at the base end and using a plug base, whereas I could do nothing to make the Thompson magazine stronger. In the end, I picked the Grease gun magazine for its many advantages and few weaknesses. Experimentally, I tested a Grease Gun magazine to find out how many 10mm cartridges fit inside without modification. I was able to get 36 to 38 10mm’s to fit in the magazines and I believe that 40 would fit by trimming the follower a little and without damaging the spring. This is better than I hoped! That means that a single man, with one triple pouch on his hip, could carry 160 rounds on his person as well as the load for his sidearm, which would be compatible! After a few mins of testing I found this to be true. Forty rounds was easily achieved and after leaving the magazine loaded for a month, found it functioned perfectly.
Next: The Barrel
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