I sent my replica in to have it turned into a death machine by Umbrella with all the bells and whistles, and that they did. It’s run 10k bbs without a single issue and with some of the most insane performance and consistency I’ve ever witnessed out of an airsoft gun. However, they changed my buffer tube out(it was an M4) and when I emailed them about it I got no response. G&G evidently have a proprietary buffer tube and my factory stock won’t work anymore, which is, believe it or not one of my all time favorite features on all the m4s I’ve been around. Really wish I would’ve gotten an explanation because I’m confident that they didn’t change the buffer for no reason but at the same time my un-educated self can’t figure out why it would make a difference. Every other question or concern was promptly answered with a text, email, or even a phone call. But when I got the rifle back and my stock didn’t work I emailed them and got no reply.