outer/inner barrel for KING ARMS casv-m

[sickboy76]

Hey all picked up a casv-m the other week! unfortunately it comes with a truly horrendous flash hider/short barrel combo!
At the moment it's got a barrel extension and new flash hider that the shop slapped on and seems to be firing ok,there seem to be no problems with the shorter inner barrel. I'm aiming to get a barrel on it after christmas so thst the flash hider sits outside the handguard but not really sure what length inner/ outer barrel I should get.

For the record the handguard length is coming in at 9 and a half inches!

any advice would be much appreciated