We all know sixmm is dodgy as feck but
https://www.sixmm.com/en-gb/products/guns-modify-tokyo-marui-mws-gbb-ach-style-charging-handle-fde
Even they're taking the piss at £190 😂
Personally I’d ditch the maxx hop unit in favour of a ZCI polymer rotary unless the maxx somehow actually works
You’re also running hot, 1.24j is roughly 365 FPS
As long as the paint is able to stick to the surface you can use it. Most airsoft replicas are Aluminium and/or polymer, which most paints can adhere to without issue