I heard all of those stories about how tough Nilgai were so on my first hunt I carried a 416 Remington Magnum just in case. My hunting partner didn't want to shoot the 416 and only had a 7 mm RM. The outfitter required a 30 cal or bigger so I told my friend to bring the 7 RM and If ask, just tell him it was a thirty cal. We hunted together and spotted for each other and had the rifle covered.
He used a 150 grain partition and I convinced him that the 7 RM was plenty big for anything that didn't want to kill you. We flipped for who went first and he won so I spotted for him. I knew his load and drop so My job was to range for him and feed him MOA to use.
The first hunt, we got a chance to prove that the 7 mag would do it and after spotting a big blue bull I walked him in at just under 700 yards. Calmed him down and he did the rest. One shot through the lungs and after about 80 yards the bull went down. I shot mine at 360 yards with the 416 RM and a 350 grain A Frame and he went about 20 yards.
Both were shot through the lungs and no follow up shots were needed. As said, shot placement is the most important thing and the 7 RM proved to me that It was capable and up to the task. I don't think Swift makes an A Frame in 7 MM any more but if you can find them that would also be my choice.
knowing the animal and the possible distance, and also the eye site of the Nilgai , My preference now would be the 338 just In case. (We saw bulls at more than 900 yards But felt that ether rifle would be pressed to make those shots.
J E CUSTOM