This should give you an overall idea of an G&G Mp5 .... since yours is blowback, the only hard part is to open your gearbox .... The blowback version does not have easy upgrade access. My friends and i took 2 hours and never found out how to disassemble a G&G M4 blowback .... they are a pain for nothing. Though , they WILL take any others mods & upgrades from your M4's internal and external upgrades. Just the cylinder that needs to be slightly modified because of your blowback feature.