Ive worked on the stoners, really not impressive. I dunno if they fixed this, but the last two I saw the bushing holes were off between the two halves of the shells causing the spur gear to rub on the shell and eventually break. Proprietary shells and they needed to be replaced. You can modify a normal v2 shell to fit though.
The ammo feed system was retarded. And the hop chamber/barrel setup was also stupid. Whole gun seemed pretty rushed in design.