I don't know about the difference of the Guarder/Systema items, I didn't ask but I'm also wondering. My guess was that's a mix of te 2 brands deppending of what they have, but I'm far from a gearbox expert, this why I bought one already upgraded.
If the motor is struggling for cocking the spring, it must be why they highly recommended the use of a lipo set-up ^^
And it's 0.2g bbs. Here's a picture of the chrono with my stock barrel.