I have some characters that need to have lightweight firearms. Research is telling me that while aluminum guns HAVE been made, they require special ammunition to avoid misfiring. What other material options do I have? Carbon fiber?
There are a lot of firearms that incorporate aluminum alloy components to reduce weight. This is fairly common, though not as popular today as it was twenty to thirty years ago. There are still a lot of popular, well respected, aluminum frame pistols and rifles on the market, including the Baretta 92s (including the M9), and the SIG P226 (though there was a heavier stainless steel variant sold in small quantities). With rifles in the AR15 family, there’s a lot of aluminum lower receivers in circulation.
So, if you’re wondering how that works out, there’s a critical piece of information to remember: The Barrel, bolt, and battery will be steel. In most handguns, that means the entire receiver will be, though with rifles that’s less certain.
Weight is, already, a huge consideration for firearms. This is why a lot of pistols used aluminum frames, and their manufacturers have since moved on to polymer frames. Similarly, a lot of rifles have moved over to polymer furniture to reduce weight. Carbon fiber is an option for some common firearms, for example, you can replace the walnut stock of your Remington 700 with a carbon fiber variant. This will set you back around $600 dollars, though the actual weight reduction is debatable.
Off hand, I’m not aware of any pistols with carbon fiber frames standard. (Only a few high-end “designer Glocks.”) Though, that’s probably a matter of time as well.
There’s also some oddities like the Professional Ordinance Carbon-15. This was an AR-15 pattern rifle that had a bunch of its components replaced with plastics, including the lower receiver. The early examples were rather fragile, but it did deliver a 5.56mm rifle at around four pounds.
Beyond swapping out the materials, there are a couple things someone can do to reduce the weight of a firearm.
Porting is the practice of cutting out unneeded material. This may range from simply cutting into a slab of metal or plastic, or it may involve cutting full slots through it.
On rifles, one option is to remove or redesign the stock. At the extreme end, this can involve replacing the stock with a simple wire structure, or a sling system. Worth noting: this is not an option with AR15 pattern weapons, including the M4 and M16. These rifles incorporate their gas return system into the stock.
In contrast, the AK family of rifles have gas return systems that run over the barrel. This means you can completely remove the stock from AK pattern rifles without ill effect. To be fair, the AK takes this design decision from the StG44, and any other rifle that patterned off that design, like the FN FAL, or H&K G3 will (usually) have a similar gas system.
One quick way to do some of your work for you would be to look for paratrooper variants of existing rifles. These are designed to cut as much weight from the weapon as possible, without sacrificing structural integrity. These often feature shortened barrels and collapsible stocks to reduce the weight.
Another option, depending on your characters’ objectives, would be to use SMGs instead. These are (usually) going to be considerably lighter than full rifles, though you’re losing the power, and range of a rifle, in exchange for a lighter, more compact weapon. For example, an H&K UMP45 is a little over half the weight of a full sized assault rifle, and is already firing a subsonic round. You can’t use it at long ranges, but if your characters are slipping in undetected, it will be far easier to conceal and much lighter.
There are, also, already a wide range of weapons intended for clandestine use. It’s easy enough to come up with a scenario and say, “well, this is unusual, I don’t know how I can equip my characters for this.” But, when it comes to military hardware, it’s often helpful to remember that weird scenarios with strict equipment requirements are something special forces groups plan for. Beyond that, it’s often easy enough to find out that, “oh, this rifle variant was designed specifically for situations like the one I’m looking at.”
Hell, if your special forces operator needs a completely silent tool for picking off sentries they can request a crossbow or mechanical compound bow from the armory. These same guys are going to know not to use it in a firefight, but the tool is available to them.
Lightweight firearms are a real thing. In part because no one wants to be carrying around a 30 lb rifle, unless that puppy can put a round through the engine block of a ’57 Buick.
I mean, if it’s me, and I was looking at this, I’d check what their nation of origin actually uses for hardware, and then pick something like a SIG553, H&K G36C, or an AKS-74U. For reference, my laptop weighs more than any of those three rifles.
There’s an, unusual, example that fits your suggestion at the top, and it might be what you’re thinking of, even though it’s not exactly relevant to the discussion. In the mid-60s a company called MB Associates designed and sold a 13mm pistol and carbine using a self-propelled cartridge called a Gyrojet. These are fascinating historical footnotes. The weapons had a minimum kill range of around 10 meters. (This number is a bit fuzzy. The rounds might get to a lethal velocity before this, but getting reliable ballistic data for these pistols is a pain.)
The pistols themselves were made from a zinc alloy, and were incredibly light weight. This was partially because the pistol didn’t need to deal with the explosive forces a conventional firearm.
To the best of my knowledge a little over one thousand of these were produced. There’s at least four variants, two pistols (chambered in 13mm and 12mm) and a few rifle and carbine variants. I know of a few other prototypes, though I have no idea how many of those existed.
These days, unspent cartridges are exceedingly expensive ($100-$200 a round), and the extremely light weight can leave you feeling like you’re holding a toy, rather than a real, functional, firearm.
MB Associates was hoping to land a military contract, and some of the pistols did see use in Vietnam. Unfortunately, the minimum lethal range was a serious flaw. Beyond that, the rounds themselves suffered from production issues, resulting in wildly inaccurate shots. The bullets had four angled ports, which, once the propellant was ignited, would keep the round moving, and would cause the round to spin, stabilizing it. Unfortunately, on some production cartridges, one of those ports would be partially obstructed, meaning the round would corkscrew unpredictably in flight. I’m honestly unsure if this is more horrifying or hilarious.
I don’t have hard data on exactly when MBA went under. I want to say it was in the early 70s. Either way, this remains a weird historical footnote. It might be what you’d heard about, even though it’s not exactly relevant to your question.