Its a P90, it literally needs almost no cleaning, lube or oil. Its a direct blow-back rifle. Wipe the excess coating out of the chamber with a qtip and a good solvent, every few 1000 rounds or so.

My gen 1 has never had lube, and the bolt has never been cleaned, I just clean the chamber. Never had a single stoppage that wasn't a dud round with a good primer strike. Worst damage it has it surface rust on the bolt, barrel is still perfect factory chrome is 100%. It has over 30k rounds though it now, coming up on 40k. I wipe down the barrel and charging handle to stop rust once in a a while.

The worst damage you get is the front of the trigger pack from the cases bouncing off, just stick some velcro on there to protect it. I have to replace it as it wears though.

And lastly there is 0 reason to ever unscrew the stock normally unless you want to paint it. Its 10 screws with non captive nuts. You can remove everything from the stock without unscrewing it.

FN factory test fires every gun 3 times to check for cycling, having a defect you could see with a disassembly would be incredibly rare.