You can say a lot about Knight’s Armament. Their products are super high-quality weapons that set the standard in the AR market. You can say they don’t produce enough SR-16 rifles making it tough to get one at the MSRP price point. What you can’t say, though, is that the company isn’t creative. Knight’s Armament has always been willing to find creative solutions to unusual problems. One such example is the KAC Masterkey.

The Problem – The Masterkey Solution

The KAC Masterkey was a solution to a problem Delta Force had in the 1980s. They often came up to doors, and those doors were locked. Setting up explosives wasn’t always an option, so the shotgun was often called forward. This required an operator to carry a separate weapon for breaching and that created complications for that operator.

Trust me, as a dude who was once issued an M16A4, M9, and a Mossberg 590A1, it becomes a real pain in the ass to carry them all while climbing, getting in and out of vehicles, and doing any task besides walking in a straight line. So, the need arose to simplify the entire process without compromising the operator’s capabilities.

Knight’s Armament went to the drawing board and clearly saw an easy solution to a complicated problem: They mounted a shotgun to a rifle. After all, the M203 had already proved that mounting a grenade launcher was possible. Knight’s Armament developed a method to attach a Remington 870 to the bottom of an M16 or M4 rifle without permanently altering the rifle.

Knight’s designed a custom mount to make it easy to attach the 870 to the rifle. The shotgun extends slightly past the barrel of an M4, but not too much.

The 870 In Action

The Remington 870 makes perfect sense in this role for a variety of reasons. It’s a dependable shotgun platform that was well-proven and already in the arsenal of most military forces. Its main competitor was the Mossberg 500, but the Mossberg’s top-mounted tang safety made it a non-starter.

A pump-action shotgun is also a must for this role. Semi-auto shotguns are great but wouldn’t work for numerous reasons. First, in the 1980s, semi-auto shotguns were still a little finicky, and making one short enough to work would be tough. Second, a semi-auto shotgun won’t cycle the light-loaded breaching round used to destroy locks and hinges.

Getting Awkward With the Masterkey

The Knight’s Masterkey has a short 9.5-inch barrel with a very small pump. I imagine the pump was trimmed and shortened to reduce bulk and the possibility for it to catch onto something. The short 9.5-inch barrel necessitates a short magazine tube that holds only three rounds. With another in the chamber, you get a total of four rounds.

There is no grip for the Masterkey, so you have to use the magazine as a grip. As you’d imagine, it was quite awkward. However, this wasn’t a huge deal because the Masterkey itself isn’t a fighting weapon necessarily. It’s designed solely for breaching doors. The rifle it’s attached to is the fighting tool. Trying to use an under-mounted shotgun as a fighting tool would be extremely awkward.

Trying to work the pump and use the magazine as some weird form of pistol grip would make it a superbly awkward fighting weapon. On the other hand, placing it point-blank against some door hinges wouldn’t be a big deal in the awkwardness department.

Speaking of awkwardness, despite the lightness of the M203, the weight of the Masterkey made the rifle a little unwieldy. Masterkey adds five pounds and four ounces to the front of the gun. This created a lot of unbalance. It also made gripping the rifle quite awkward and certainly added some pressure to the barrel.

As you’d imagine, the Masterkey wasn’t a tool that was widespread on Delta’s rifles and was mostly used in case of emergency. I’ve only been able to find one picture in the wild of the Masterkey in the hands of a Delta operator.

The Modern Model

The Masterkey inspired the US Army to create the M26 MASS shotgun.

The M26 is a magazine-fed shotgun with a straight-pull bolt mounted to its side. It’s much more ergonomic and allows the operator to quickly reload if necessary. It can also mount to a rifle but can also quickly turn into a stocked shotgun.

Nevertheless, the M26 is very rarely issued or used. It simply gives soldiers another tool for the box when necessary.

Mastering the Masterkey

While the Masterkey was a limited-use tool, it had a specific niche in which it was invaluable.

Knight’s Masterkey provided a true Masterkey for any situation a Delta operator might encounter. Sometimes, a door needs to be opened, and a brick of C4 or a Carl Gustav isn’t an option.