Yes, all the above posts are correct, the following RS parts will work:
-RS fire selectors (mods to the auto sear, trigger, sear
-Rails
-Upper receiver Sets
-Flash hiders (rethreading of outer barrel required)
-Takedown pins
-Detents
-Detent springs
-Charging Handles (with mods)
-Pistol Grips
-Buffer Tubes
-Stocks
-Castle Nuts
-Delta Rings
-Antirotational Pins (mods to the lower receiver required)
-Magazine Catch
-Endplates
-Fire Safety detent and spring
-Recoil Buffers
For interals, I recommend these parts:
-CWI trigger set
-Ratech steel bolt + aluminum nozzle + steel nozzle guides
-Ratech fire pin and delayer
Real Steel Parts
Vltor Modular Upper receiver (MUR 1A)
Vltor 5-Position Receiver Extension Tube
Vltor Gas Block GB-2S
Magpul CTR stock Commercial Size (Black)
Magpul Enhanced Rubber Butt-Pad, (0.70")
Magpul MIAD Full Grip Kit (Black)
Magpul PMAGS (Black)
Gear Sector Hand Stop (Black)
BCMGUNFIGHTER Charging Handle w/ Mod 4 (MEDIUM) Latch 556
Troy OEM M4 Sling Mount
Troy Front Battle Sights with Tritium(Black)
Troy Rear Battle Sights with Tritium (Black)
Troy Rail Cover Full Length (Black)
Troy Rail Cover 3” (Black)
Troy Modular Combat Grip
Centurion Arms C4 Rail System 7”
Streamlight TLR-2
Eotech 552.A65/1 Holographic Sight
Norgon Ambi Magazine Catch
Battle Arms Development Ambidextrous Safety Selector (BADASS)
KNS Gen II Non-rotating Trigger/Hammer Pins (0.154”)
Daniel Defense Magazine Release Button
Daniel Defense Castle Nut
Daniel Defense AR-15 Front Pivot Pin
Daniel Defense AR-15 Rear Takedown Pin
Daniel Defense Magazine Catch Spring
Daniel Defense Selector Detent
Daniel Defense Selector Detent Spring
Daniel Defense Takedown & Pivot Pin Detent
Daniel Defense Takedown & Pivot Pint Spring
Daniel Defense Carbine H-Buffer Assembly
Unknown Real Steel Delta Nut
Airsoft Parts
CWI AW Forging Steel CNC Fire Control Unit for WE GBB
RA-Tech 6.01 300mm Inner Barrel (custom cut/crowned to 245mm)
RA-Tech CNC Firing Pin Base and Valve Locker WE GBBR
RA-Tech CNC Steel Bolt Carrier WE M4/M16 Open Bolt
RA-Tech Nozzle Guide for WE GBB M4 (Open Bolt System)
WE M4 Open Bolt Kit
King Arms Air Seal Chamber for Marui GBB Pistol / VSR
King Arms Noveske KX3 Flash Suppressor Steel Version (14mm CCW)
PMC Noveske 7” Outer Barrel
G&P DBAL Dual Laser Destinator and Illuminator
Mad Bull Surefire FA556 MINI 5" Silencer
Here are my links to help you:
.::::WE M4 Real Steel/Airsoft Build NOVEMBER 24, 2011 COMPLETE (last post)::::.
http://www.airsoftcanada.com/showthread.php?t=122347
.::RA-Tech WE M4/M16 Steel Bolt Tutorial::.
http://www.airsoftcanada.com/showthread.php?t=130612
.:::RA-Tech Versus CWI WE M4/M16 Steel Trigger Kits- Which To Buy?:::.
http://www.airsoftcanada.com/showthread.php?t=132679