![]() ![]() ![]() ![]() The cartridges will ride on this bump, reducing contact against the rear, and hence friction. Our magazine will be stronger and more rigid, but this will also provide a place to weld the gap together, since the magazine will be formed from sheet steel. When you take that thought into consideration, you'll realize that the front of each bullet is riding on the magazine by an extremely small point, which reduces friction.Īt the rear of the magazine is a bump inwards. Don't worry about the fillet towards the front intersecting with our box - Bullets usually aren't squared off like that, but instead come to a point, so there can be a little bit of intersection. It is basically a box, with rounded corners. Here I've sketched the main profile of the magazine. Any wall built to contain the cartridges will have to interact with them at these points, since they are where the protrusions are. I start a new sketch on the top plane and lay out the critical outer dimensions for my cartridge. This also gives you a starting point for your tolerancing. Using the maximum dimensions means that all ammunition should fit in our magazine, unless it is improperly manufactured. Instead of the complicated reinforcing piece atop the head of the magazine, mine will simply be made of a higher grade, heat treated steel sheet.įirstly, I obtain the maximum outer dimensions of the cartridge I'll be using from the SAAMI performance standards document relevant to my needs. While this magazine design is not very good, it is quite functional and easy to make. In this example I'll be designing a double stack, single feed magazine for 9mm Parabellum, much like the STEN or MP40 magazine that have been copied and modeled time and time again. Step 3: Example in practice: a 9mm SMG mag.The designer must figure out ahead of time what features are important for both the function of the final product, but also manufacturing concerns and the overall lines and aesthetic of the firearm it will fit into. This is to accommodate the taper of each cartridge, rims, a handgun's grip, and so on. Many magazines are curved or slanted in some way. These also have the added benefit of increasing the rigidity of the magazine. This is usually done with a series of inwards ridges that control the horizontal motion of the cartridge whilst minimizing the contact with the walls. However in higher capacity magazines, magazines that require a fast response time, or to minimize the possible effects of dirt, less contact with the cartridges is preferred. For lower capacity, and usually single stack, magazines this is not a problem. However, contact between the sides of the magazine and the cartridge body generates friction, necessitating a heavier spring. You can design a perfectly functional magazine that is a simple box that contains cartridges and moves them towards a feeding device. Feeding these cartridges out of the magazine is either accomplished by sorting the two stacks into one, or feeding from either stack alternatively. Two complete stacks of cartridges ride side-by-side, offset vertically from each other by one half the cartridge diameter. It is as easy to manufacture and design as possible.Ī double stack magazine is slightly more complex. It is comprised of a single column of cartridges, one on top of another, propelled upwards by a spring. While much of the ideas behind designing a magazine are "standard" between designers due to their functionality, there are still important decisions to be made as to the exact construction of your magazine design.Ī single stack magazine is simple to understand and design. While European counterparts exist, I live in the United States, and any cartridge common enough for me to design anything for is covered by SAAMI. This organization provides the standards for US companies to aspire to while manufacturing ammunition, and gives this information out to the public, on the internet. You can gather your dimensions from physical examples with varying degrees of success, but for exact standards I recommend the Sporting Arms Ammunition Manufacturers' Institute or SAAMI for short. While certain elements of magazine design carry over between cartridges and requirements, exact dimensions are key. In order to design an effective magazine, the cartridge required must be known to the designer. The concepts touched on here cover both simpler designs, and more complex. This tutorial will cover design of a slightly above basic firearms magazine. ![]()
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