This is a Big Fearsome Drill replacement for Hasbro 2016 Combiner Wars Nosecone. Of course it can be used for custom Drillhorn as well.
Per forum member suggestion, the drill is slightly modified with a 5mm post in the back so it can be used backwards.
Note for this design the turret of the tank must be moved forward for the drill to attach at the front of the tank, but it makes the proportion odd. I recommend you check out "BFD 2016" which is better looking and does not cost a lot more. If you just need a drill check out "BFD 2005".