I just wanted to know if it has a metal one piece hop up, because I know it is has a full metal body.(Might buy it soon)

No, it has a plastic hop up. It is a different design than other M4s, so it also has a different nozzle. If you want to switch hop up units, you must swap out the nozzle also.

According to KWA, this design gives better compression, but it also is hard to get a barrel and bucking to fit. (I suggest a promy barrel and stock bucking with an H nub. That combo almost always works)

This and the fact that they have trouble with midcaps drove me away from KWA. Some work for some, others not at all. I wasn't about to risk 50+ on mags that might not even work.....

I'd rather have one of these
http://www.airsoftgi.com/product_info.php?cPath=139_24_107&products_id=3434

KWAs are very nice internally, but they are over rated. They are not "indestructible" as some people say. They are great guns, but just stay away from lipos. A 9.6v gives you around 20 rps which is plenty fast.

I usually use high caps anyway. So, to improve the accuracy/range/fps get the H nub with the stock bucking and a Prometheus 6.03 TB barrel.

Yep, you got it

Thanks for the help.

Yep, glad I could help

You might want to get the 407mm length barrel. The KWA M4A1 barrel is like 394mm instead of 363mm. According to posts on the KWA forum, (kwausa.com) the barrel barely sticks out of the outer barrel, so it will be fine if you have the flash hider on.

I got the standard M4 size barrel, whatever that is, and it works out fine. Better than fine. Oh, and the mags I have were like 18 bucks each. They came highly recommended from AEX. They are midcaps. They work Great. But other than that, I almost agree with you on everything else Hop up is plastic. It is a pain to find a bucking that will fit, best to stay with stock. And there is really no need to use a Lipo, it preforms great with a 9.6v. 22 rps fully charged. 16 rps halfway charged

Ha ha, that reminds me, last time I was at my field, some kid with a KWA was using a Lipo for like four hours and the battery actually started to sizzle. After a while, half of the battery was melted away. luckily he took it out before it melted into the gun.

But I digress. You get the point.

Oh, its new to me ( :