Well my G&G MP5A4 is the only gun of the 12 or so I've owned (apart from pistols) that I haven't touched the internals of. I've only ever cracked it open once, just to find out how and it's immense!
No call even for a tight bore or new hop. For CQB it performs above and beyond the call of duty and the spring is still shooting perfectly at the same fps as when it was new, after over a year and it has seen some pretty heavy use, from numerous people. I often take it as a spare as my mate's guns are prone to breaking if they so much as touch them, so for my MP5 to have withstood their rough handling and not needed upgrades for me to feel it's performing as it should... Well, it's the best gun I've ever bought, hands down. Put it that way and at £220 it's the cheapest gun I've ever bought new as well (apart from pistols).
The only one I've never had a single issue with.
Range is lacking for woodland - but meh, it's supposed to be a short range weapon.
It even has a snazzy blowback system, which is full travel and doesn't get stuck in the middle AND it sounds epic.
Get the G&G or I'll haunt you forever lol
