Modern Intermediate Calibers 009: The 6x35mm KAC/TSWG

Nathaniel F
by Nathaniel F
The 6x35mm KAC/TSWG flanked by its parent, the .221 Remington Fireball on the left, and the 5.56x45mm on the right, which it is designed to duplicate from shorter barrel lengths.

The 6x35mm TSWG, also commonly called the 6x35mm KAC, is a round shrouded in mystery. Apparently designed by Knight’s Armament Company for the interagency counterterrorist program cryptically named the “Technical Support Working Group” alongside the PDW with which it is popularly associated, the round was apparently never adopted. However, it is interesting primarily as an example of a round with shorter overall length than the standard 2.2-2.3″ (56-58mm) OAL that has become ubiquitous for modern intermediate rounds. The 6x35mm TSWG was designed solely for the unique KAC PDW, but a more traditional AR-15 type rifle called the SR-635 was also chambered for it. Like the .300 Blackout, the 6x35mm was also designed explicitly for 10″ or shorter barrel lengths; KAC has advertised their PDW as being available with 8″ or 10″ barrels. To properly compare the round with both the .300 Blackout and 5.56mm, we will be looking at estimated velocity figures from both 9″ and 14.5″ barrels, although it should be noted that so far as I know, no weapons chambered for the 6x35mm cartridge actually exist with barrels of either of these lengths:

Although not as good a ballistic performer, the 6x35mm KAC is somewhat lighter than the 5.56mm, at about 10.7 grams per round.

Note: All ballistic calculations are done with JBM’s Trajectory calculator, using the ballistic coefficient appropriate to the projectile being modeled, and assuming an AR-15 as a firing platform. Also, keep in mind that there is no single true velocity for a given round; velocity can vary due to a large number of factors, including ambient temperature and chamber dimensions. Instead, I try to use nominal velocity figures that are representative of the capability of the round in question.

Nathaniel F
Nathaniel F

Nathaniel is a history enthusiast and firearms hobbyist whose primary interest lies in military small arms technological developments beginning with the smokeless powder era. He can be reached via email at

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  • Fox Hunter Fox Hunter on Aug 14, 2016

    My favorite intermediate cartridge, good enough up to 300 yards, and from short barrels at that. Even better than 300 BLK. Someone should make guns and ammo in this caliber.

  • LilWolfy LilWolfy on Aug 21, 2016

    I think the 6x35 PDW is overlooked by many, so glad to see it here. It makes a lot of sense for support personnel, crews, and low signature work, but would require a massive change to the logistics system since it is appropriate for so many Soldiers, Airmen, and Marines.

    If they increased the BC of the projectiles and still fit it in those short COL mags it has, it could probably hit 5.56 retained energy at distance and catch up to it. You can carry so many of those mags, more like an SMG. It packs a lot of firepower in a very compact and lightweight package when looking at soldier's load. You can easily carry 10 mags in the space that would normally take 6 NATO STANAG 5.56 mags. That's a big deal in the era of body armor.