Complex sentence: A version of the gun in 13 mm (13x92mm TuF) the Gast-Flieger MG, was also under development; it used the same ammunition as the Maxim MG TuF and had two, curved, box magazines.
Split into simpler sentences: A version of the gun firing 13 mm ammunition (13x92mm TuF), the Gast-Flieger MG, was also under development. It used the same ammunition as the Maxim MG TuF and had two curved box magazines.