Based on the Western Arms gas blowback mechanism., the AGM M4 CQB-R2 Gas Blowback is at a reduced price of US$144.70 at Tiger111HK. As typical of gas blowback rifle releases from AGM, this one does not come with the trades, but you can check out third party receivers for the WA GBB-Rs that may fit the AGM... "Enjoy the Gas Blow Back M4 with low price!! Replica of WA M4 Gas Blowback Mechanism:

• Full Metal Aluminium Body (No Marking)
• Metal Made CQB Type RAS Front Set
• Quick Detachable Front Sight
• Over 350FPS Velocity Muzzle
• Functional Metal Bolt Carrier - bolt stops when magazine is empty just like a real steel
• Extendable Stock
• Heavy Weighted Full Metal Gas Operated Magazine
• 50 round loading capacity
• Adjustable Flip Up Rear Sight
• Adjustable HOPUP
• Aluminum Made 14mm Counter-Clockwise Flash Hider
• Sling mount can be installed with any single, 2- or 3- point tactical sling
• Remember to check out our Store for accessories"