Most firearms are best known by their action, or by their caliber, or by their purpose. Shown at the fall, 2016 Big 3 East event, the Boberg XR9S, more recently rebranded as Bond Bullpup, is defined mainly by its extremely unusual magazine. Internally, this compact rotary breech 9mm pistol resembles the old Vickers belt-fed machine gun. The feeding process happens in two stages, the first — picking up of the cartridge from the magazine — on the rearward slide motion, the second — chambering of the cartridge — on the forward motion. Unlike the machine gun mechanism developed to cope with rimmed ammunition, XR9 solved a completely different set of problems.
For one, this arrangement allows a much longer barrel for the same length slide. The additional length is roughly equal to the length of the cartridge, 1.5 inches. And additional benefit accrues to reliability, as each next round is already in place before the feed cycle begins, making magazine spring strength less of a consideration. Further, the angle between the cartridge and the chamber is zero, so any profile ammunition that fits the magazine will feed reliably. Doing away with the unnecessary feed ramp strengthens the chamber for increased safety margin. Lastly, the reduction of magazine spring pressure allows dispensing with the follower, for an extra round of increased capacity.
The rest of the pistol is equally unconventional. The rotary breech is supported at multiple points for practical accuracy quite impressive for a pocket gun: at fifty yards (!), hits on an 8 inch head-sized plate are routine. Each pistol comes with user-interchangeable trigger springs for 6 and 9 pound pull options. The extra-compact DAO trigger of original design is smooth and constant throughout its arc of travel. It provides re-strike capability, a helpful option for close range.
The combination of the rotary lockup and generally low-energy feed cycle allow substantially lighter recoil spring than typical for tilt barrel designs of the same size. Even physically limited users can rack the slide, and felt recoil is on par with conventional autoloaders of nearly twice the weight.
Do all these amazing benefits come with down sides? Certainly, but you can judge as to their significance. Since the feed cycle requires full back and forth slide travel, there’s neither a slide stop nor any use for it. The rearward acceleration of each cartridge during feeding can kinetically pull the bullet from uncrimped cases, though whether that’s a greater problem than the bullet setback and resulting overpressure is open to debate. Rotary action is also not conducive to thread-on sound suppressor use.
After creating the highly reliable 9mm subcompact pistol, Boberg Arms faltered on adapting the design to 45ACP and design passed to Bond Arms. Re-branded Bond Bullpup, the XR9-S is expected to be re-designed slightly for a re-release in early 2017.
For more information please view http://www.bobergarms.com/