This is yet another firearm design intended to fill the role of a personal defense weapon, hence the appellation of PDW. The idea behind the PDW concept is that soldiers in support functions are overly encumbered by full size rifles and carbines, but under armed with 9mm sidearms. This weapon comes to us from CBJ Tech AB in Sweden. The MS stands for modular system. And the CBJ/MS is capable of firing standard 9mm NATO rounds or their proprietary 6.5x25mm high velocity armor piercing ammunition.
The CBJ is somewhat obviously based on the IMI Uzi submachine gun, building off the design innovations of a well proven system. Like the Uzi, it is blowback operated and uses a telescoping bolt. It has several differences, though. The charging handle has been moved to the rear of the receiver to allow easier manipulation close quarters. The CBJ/MS barrel is designed to be quick changed in the field by the user to switch between the available calibers. It also lacks the grip safety of the Uzi series. Fire selection is in the manner of the Steyr AUG, via your finger. The trigger is the only fire selection input- a short, lighter pull results in a single shot, and full-length, hard pull enables full auto fire. The standard version fires from the open bolt, but a kit is available to convert to closed bolt operation for higher accuracy in the first shot. The system has most of the modern extras, optional bipod, collapsible stock, Picatinny rail for the attachment of optics, backup iron sights, and an ambidextrous, non-reciprocating charging handle. Another neat feature is that the foregrip can hold an extra 20 or 30 round magazine. I'm pretty sure that it feeds from standard Uzi mags, but don't quote me on that, it seems that it would though. I would have liked to see a muzzle brake or flash hider with the capability to mount a suppressor, though.
9x19mm NATO and 6.5x25mm
At the heart of the system is its new high velocity ammunition. The type is called the 6.5x25mm and comes in several different loadings. The main version fires a 4mm, 31 grain saboted tungsten bullet. This projectile is rated at 2723 FPS and can reportedly penetrate a NATO standard CRISAT armored target at 230 meters or 7mm rolled steel at 50 meters.That is pretty good armor piercing effect.
The system can be used with 6.5mm bullets of different construction (tungsten, jacketed lead, etc.) as well. The secondary loading is intended for unarmored targets and is a "spoon-tipped" 4mm bullet designed to tumble quickly and cause serious damage through a large wound cavity.
The 6.5x25mm CBJ can also be used in almost any modern 9mm weapon, provided that the barrel and return springs are replaced. This is possible as the 6.5 CBJ is made from a necked down and stretched 9x19mm NATO case. The same magazines can be used. This introduces the option of converting 9mm pistols and submachine guns in stock to PDW type weapons with inherent armor defeating capabilities.