#6x35mm

When I started the Modern Intermediate Calibers series, I did not expect it to grow as large as it has. The initial plan was for 7 major calibers, which grew into well over 20, and the spinoff Modern Personal Defense Weapon Calibers, which itself will have at least 20 entries.

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:

Anthony Williams, small arms theorist and co-author of the book Assault Rifle with Maxim Popenker, wrote an article in February of 2006 on the development of the Personal Defense Weapon and its ammunition, which he amended in late 2013. He includes in the article two photos which together represent one of the most complete collections of PDW cartridges I know of: