KWA SR5 Parts and compatibility

[bezz]

Hey guys

I need a little help from someone who hopefully has experience on this subject. im looking to get an extended barrel on my SR5 as i want a longer tight bore barrel that what it comes with as stock. ive read that KWA is a pain to get parts for as they make there guns slightly different from other AEG's.

Does anyone know what brand of outer barrels and inner barrels work with the KWA M4 series?

and what other upgrades have you guys got? Need ideas

Thanks guys