If I remember correctly, you detonate the mines by pressing number keys.
45mm is Thunderbolt's exclusively and since it is designed to carry only that weapon ("gatling gun"), we did not choose to give it any other primary weapon choices.
Aurora on the other hand can use 60mm although it drains energy reserves very quickly (designed for Badger). 42mm and 43mm are Raider weapons. They suck compared to EA arsenal.