Moran.m44
Welcome to the forum.
I have not hunted Nilgai personally. It is my understanding that they average in the large cow/ young bull weight range of elk. With that in mind I think your set up with a razor sharp broadhead placed in the vitals at tradbow ranges ( max 30yds for most of us) will work fine. If you are interested in enhancing the penetration capabilities of your arrow, go to our– friends of foc forum- and review some of the discussions there. The ability to place a razor sharp broadhead exactly where you want it ( i believe in some of the exotic antelope the vitals are more forward, so I would study Nilgai anatomy) is the prime consideration, which for me means I practice a lot.
Scout