What length barrel will fit a Classic Army M4 CQB?
Not sure on length but try a KN/TN 6.04 barrel. They are solid and work great.
I have always acted in self defense, occasionally pre-emptive self defense.
http://cgi.ebay.com/Systema-6-04-BS-Airsoft-AEG-Inner-Barrel-285mm-Z-09-31_W0QQitemZ270267313735QQihZ017QQcategoryZ31681QQtcZphotoQQcmdZViewItem?refid=store
You NEED a replacement or looking for better accuracy etc?
NEED a replacement. the Inner barrel is broken.
Prometheus over systema all the time. Look at DB Customs barrel. For the price they're pretty decent.
Pygmy Militia Group