Finally, an M4 electric feed magazine from Battleaxe which is available at RSOV.com... "M4 / M16 800 rds electrical-feed double magazine powered by 4 x commercial AAA batteries and can be easily accessed by removing the dummy magazine floor plate. The spring winding can be activated by the local push button at the front of the dummy magazine and the copper fake bullets magazine top can be slided open for easy bb filling."