ACTION ARMY Custom Outer Barrel for AAC21 / KJ M700

very good

I quite enjoy the build quality of this product, it is definitely shorter than the stock barrel so you will need to take that into account. Also, this will not fit directly into a KJW M700 body, being a bull barrel means it's too wide to fit, and will need to Dremel down the stock in order to have the barrel fit. Once you do, all other attachment points line up perfectly, though I did use the stock mounting screw for the barrel instead of the one that comes with it, as the one it comes with I found was not long enough to allow the front bipod mounting point to grab it correctly.