A prototype for an adaptable platform.
It's chambered in a proprietary short cartridge, with identical dimensions to 7.62x39, except for case length.
There are two magazine releases because the receiver is designed to be used with 7.62x39, but is currently configured to function as an SMG/PDW.
The dual ejection ports and top-mounted charging handle mean that the receiver is open on three sides. However, sides of the bolt extend far enough to completely cover the large ejection ports when it's closed, and the charging handle is mounted on a box-like structure, covering half of the top opening. The rear half of the top opening is covered by a sleeve that's part of the upper receiver.
To open the receiver, it is necessary to remove the pin at the back, which holds three things together: the upper receiver, the lower receiver, and the recoil spring guide. Once the receiver is open, take out the recoil spring guide and the recoil spring. To take out the bolt carrier, first unscrew the charging handles and remove them. Then, the bolt can easily be taken out.