I'll be putting up a diary soon, and i've used turrets from dystopian wars in some of my builds thus far
cliffnotes are as follows:
The main metal turrets are too big for most stuff. you could get away with them in some builds, but generally no.
The smaller metal turrets from the tanks are still quite big, but have potential in some builds if used carefully and/or chopped in half.
The small resin turrets are generally a good size for 'large' turrets (weapon batteries etc) but are comparatively quite tall (and will need to be chopped off the models.) My favourite is from the britannian frigate, though the brit escort and french flaktank turrets are also pretty great)
The best turrets i've found for turrets are press moulded off the metal bomber models (particularly, the brit and prussian ones)