An Ideal body kit and rail for AR would be MRP from LMT company, solid 1 piece upper and rail. It's a pity that the WE won't fit in a real steel MRP upper, and the only MRP kit for GBBR is Prime spec. Go with the URX kit I'd suggest, MK18 and DD 7.0 are flooding on the street right now.

Bad idea the URX : G&P makes it for WA based and would need to rethread the upper receiver. Plus you need a special tool to mount it.
Take a 7" DD that if possible, uses the regular AR15 barrel nut to avoid incompatibilities. The 7" will also permit to put on a short stroke piston system. If I recall LWRC puts that on all their guns now.

My Real Steel Mk18 RIS is on my AEG back in HK, got it from a contact i have that goes to Duke university in North Carolina, paid about 3500 HKD for it about 450 CND? but yeah

http://www.airsoftcanada.com/picture...pictureid=1373

Its an AEG btw

Magpul Enhanced M4 Lower, VLTOR MUR-1 Upper Receiver (2nd Gen), Daniel Defense MK 18 RIS II Front Rail, Magpul CTR Stock, Magpul MIAD Grip, Troy Front & Rear Flip Sights, EOTech 553, Troy Flashider, Magpul PMAG, Tango Down Shorty Front Grip, ATPIAL PEQ-15

only Real Steel parts on this gun would be the EOTech 553, Daniel Defence MK 18 RIS II Front Rail, Magpul CTR stock.

another suggestion would be something like My GBB which is pretty much all Real Steel as well :) other than upper and lower dunno how you guys stick a real steel but yer

http://www.airsoftcanada.com/picture...pictureid=1354

Prime Magpul Lower, Prime VLTOR MUR-1 Upper, Magpul UBR, Magpul MIAD, LaRue 9.0, Prime Noveske 12.5" stainless outer & gasblock, Airsoft Surgeon VLTOR Bolt Carrier, Magpul MBUS, Magpul AFG, PEQ 15, Trijicon RX30, Streamight TLR-1

How does adding a 7" rail permit a short stroke piston system? isnt the rail independent of that?

thought He's building a WE gbbr with real steel parts, didn't notice he was saying G&P, the real URX is only around $500.

The 7" DD AR15 Lite Rail takes the their proprietary Bolt Up System Barrel Nut, NOT a normal barrel nut. Either way, you will have to rethread the barrel nut unless you order a Bolt up barrel nut from DD.

Since you have access to RS parts, order the nut from DD, I did and it saves you a headache.

The WE M4 WILL mate with the any AR15 REAL STEEL uppers, this is whole point of the build.

I'm using a Daniel Defense 9.5 fsp rail (Real steel) and mounted right on the upper no prob,but it was on a real steel upper on a PTW. I think these rails are alittle hard to get now.

The RS DD Bolt-up nut WILL be compatible with the WE and RS upper, someone just stated the DD Lite Rail uses the original barrel nut with the spiked flange, which I corrected.

The Systema PTW (2008) barrel nut is also not compatible with the RS VLTOR upper.

Will probably work with a lot of milling, the side walls of RS are thicker, since AR15s do not have an area for an auto sear, there is a lot of material in the rear of the receiver.

Not to mention the laws you will break for even modding a RS lower. lol

I don't know if it applies to deactivated AR15s tho, there are not many out there anyways.

Everybody has their own passion!!! Whatever turns your crank.

Sorry for the barrel nut, mixed up with a TROY one.

I was saying 7" for short stroke piston because if longer (or covering gaz hole on barrel) you will have to install gas tube and low profile gaz redirector (I don't remember the name it's been years since tinkered with AR15... HK417 all the way :D).
A piston needs some space to even the level for the piston rod. ;)