Thank you for the fast shipping @ak2m4
So as it turns out, after ordering the madbull piston, shims and motor, all I really needed was the motor!
My original concern was how quickly the motor heated up as well as the battery. When I opened it up, I noticed the piston doesn't look stock - this wasn't mentioned in the listing when I purchased it. They had mentioned a tech put in the new nub, titan and trigger, but nothing else:
Whilst the piston head wasnt the best, as it is stock, i suppose if it isn't broken don't fix it. The teeth on it look ok. However, the AOE looked a little odd at first:
Although depending on how you look at it, it's not too bad, especially when you match the next set of teeth, and consider that the previous tech put in sorbothane padding in the cylinder:
Whilst you could shave down that first tooth, the clearance seems fine. I figured I would trust the work that's already been done to it rather than complicating it further. But I will heed your advice @Speedbird_666 - if something seems off in future I'll replace the piston head as I now have the parts to do so!
I have noticed since putting it back together that the safety selector is a bit dodgy, I'll rectify that at some point this weekend.
I'm new to this sort of tech work so let me know if you think what I've decided is garbage or not lol