Hop up and schematic

[snuff]

I keep reading about hop up issues causing inconsistency,I've read up a bit .

But I was curious,are all the o-rings the same?What happens to them to cause the issues?Where are parts purchased.rubbers,upgrade barrels,etc?

I will strip my marker(s) apart when I get it (after registraion) but for now can somone guide to a schematic for an M4 or similar...thanks.