25CC Pneumatic engine V1

This is a 25cc pneumatic engine, and it's the first variant. It's estimated to have 6k rpm and 1.2Nm torque Feedback on what I can improve or add would be greatly appreciated, and I plan to create a series of inline, V, flat, and radial configurations using this design. For performance, you could use graphite dry lubricant spray on the inside of the chamber, piston, and rod. What's needed: 10 M6x12 socket heads 1 M6x20 socket head 11 M6 nuts 1 M6 washer 1 M5x30 socket head 6 M5x20 socket heads 8 M5 nuts 2 M5 washers 8 M3x12 socket heads 8 M3 washers 8 M3 nuts 2 35mm OD 16mm ID 11mm thick radial ball bearings 2 35mm OD 17mm ID 12mm thick axial bearings 1 12mm OD 10mm ID 1mm thick O-ring