Chambered in 6.8mm SPC, this Personal Defense Weapon from LWRC packs a lot of firepower into a small package.

It features a H&K-style skeleton stock which extends past a short buffer tube. This is not the most comfortable stock configuration, but it saves space. Rails or other accessories can be screwed onto the modular handguard if desired. Underneath the rail in the above photo they have attached a hand stop to prevent a user from accidentally extending their hand past the handguard and near the muzzlebrake.

[ Many thanks to Lionel the tip. ]