Complex sentence: The vehicle has no roof and is normally covered with a tarpaulin to protect the crew, transported cargo or troops from rain and snow, this makes it unable to mount any of the SGMB machine guns.
Split into simpler sentences: The vehicle has no roof and is normally covered with a tarpaulin to protect the crew, transported cargo or troops from rain and snow. However this makes it unable to mount any of the SGMB machine guns.