How do I use the Bv 238's turrets?

I have just started using the Bv 238. It's main strengths are the bombload and the turrets as you all know. But my turrets can't seem to hit or even kill anyone, causing me to go down in flames whenever anyone intercepts me. However, I am able to use other bombers' turrets effectively. Am I missing something here? Gun convergence 500m and universal belt.

And please no answers like "that's what you get for being a wallet warrior ))))".