Knight's Armament Company PDW

The Knight's Armament Company 6×35mm PDW is an experimental personal defense weapon designed by KAC, firing a new 6mm cartridge optimized for short barrel weapons.

As with all personal defense weapons, the KAC PDW is intended to be compact and lightweight (similar to submachine guns), but have a longer useful range (out to the low end of combat rifle ranges, 250–300 m).

Design details
The KAC PDW combines new and off the shelf components in its design. The lower receiver, holding the magazine and trigger assembly, is essentially a shortened M16 rifle lower receiver,which makes the basic operating controls familiar to many potential users.

The cartridge, upper receiver, and operating mechanism are all new designs by KAC.

The KAC PDW uses a completely side-folding stock, unlike the M16 and M4 designs which have their main operating spring in a tube in the stock, and therefore can only partially telescope, and not fold sideways at all.

The KAC PDW is over 10 inches shorter (19.5" vs. 29.8" with stocks folded) and more than 1 pound lighter (4.5 lb vs. 6.3 lb) than the currently serviced M4 carbine, an U.S. Army and Marine weapon and the barrel has been lightened with a new dimpling process.

Cartridge
The KAC PDW fires a 6×35 mm cartridge, a full centimeter shorter than the western military standard 5.56×45mm NATO round. The 6mm bullet is slightly wider, and the standard 6×35mm bullet is slightly heavier than the standard 5.56mm bullet (65 gr versus 62 gr).

Fired from a 10-inch (250 mm) barrel, KAC claims that the 6×35mm cartridge reaches a muzzle velocity of 2450 ft/s, slightly faster than the muzzle velocity of a 5.56 mm cartridge fired from a similarly short barrel. The larger diameter, shorter 6 mm cartridge is optimized for these shorter barrel lengths, and would perform less efficiently from rifle-length barrels. The round's muzzle energy is 831 ft.lbf versus 792 ft.lbf for a 5.56 mm bullet, again from the same 10" standard barrel.

There is a discrepancy between the velocity claimed by Knight's for 5.56 mm 62 gr SS109 NATO ammunition fired from a 10 in Colt Commando barrel (2400 ft/s, 792 ft.lbf energy) and other M-16 manufacturers' stated muzzle velocities (2627 ft/s, 950 ft.lbf). In any case the energies and velocities are roughly comparable.

Operating mechanism
According to a weapon review article, the KAC PDW has two gas pistons tapping hot gas from the barrel to operate its mechanism, located on the top left and right sides of the bolt carrier. The single mainspring is located on top, between the two gas pistons.

History
The new weapon was formally introduced at the 2006 NDIA Small Arms Symposium in Albuquerque, New Mexico. Some writers were shown samples at the earlier 2006 SHOT Show.

Usage
A PDW would be issued primarily to troops who are not offensive combat infantry, but who might need a highly capable defensive weapon if they were attacked, such as truck drivers, artillery troops, tank crews, aircraft crews, and other support troops.

Competitors
Competing weapons designs include:
 * Carbines, such as:
 * CAR-15 (Model 607)
 * SIG 552 Commando
 * Heckler & Koch G36C
 * Heckler & Koch HK416C
 * AKS-74U
 * Personal defense weapons, such as:
 * FN P90
 * Heckler & Koch MP7
 * MSMC
 * PP-2000
 * SR-2 Veresk