I am looking to make some upgrades to my G&G CAR CQB and have some technical questions. I am looking for additional range and accuracy. #1 - inner barrel upgrade - going with a Prommy but unsure about length. Stock barrel is 275mm but looking at either 363mm or 407mm. Can my gear box handle 407mm and what would be the pros and cons of one versus another? #2 - Systema Bucking w SCS nub - read a couple of threads that recommended this just unclear what it is and what it does? #3 - R hop with M nub- again what is this and do I do this in place of #2 or in addition to it? Also what is the benefit? #4 - what other upgrades would you recommend while the gun is dismantled? Thanks again and the more detail the better as I am trying to build my knowledge base!