The make is a JG, so google up JG M4A1.
Copied and pasted from
http://www.import-action.com/jgjigom4hewe.html
Soft Air M4A1 Heavy weight FULL metal airsoft rifle (Lao Bing, Soft Air)
# Metal gear box
# JG mod metal body!
# Retractable stock
# Removable top handle for RIS
# Adjustable front and rear sight
# Adjustable Hop-up system
# 340-360 FPS Max velocity with .2 bb (.12=375fps .2 with 8.4v 1400mah is at 340-350 fps, with normal battery its at 310 fps .2)
# High rate of fire 450rds / min Hi speed motor
# 275rds metal Hi-cap magazine
# Semi / Full auto modes with safety
# Battery and charger included
# Plastic body light weight
# Battery size mini 8.4V 1100mAh
# Spring grade 100
#
Make JG, Licensed by Soft Air