Just prepped 200 rounds of 375 brass I have had for awhile. Setting up my rifle for a Nilgai hunt. What bullet do y'all recommend? 270 or 300? Barnes or Accubond?

Difficult to say, but either of those bullets in that round should be great for Nilgai. Best to let your rifle tell you. Have you ever shot either in your rifle?

When I had my H&H I found the 270g allowed me to shoot about 300 yards pretty accurately. Just a little practice at various ranges and I had it. Either will thoroughly kill anything you hit with it.

I would buy boxes of 3 or 4 bullets and see what shoots best in my rifle. That said, I see no real need for an ultra premium bullet in the .375 for nilgai. Why not try the 250 grain Sierra Gameking? The bullet is comparatively inexpensive, likely to be highly accurate, and will give you a very flat trajectory. The 270 grain Hornady is also an old standby; they've typically shot very nicely in my rifles.

Accubond 260gr

250 grain Barnes TTSX at 2900fps is flat shooting and hits hard

I have used both the 260 gr. AccuBond and the 270 gr. TSX. Both shoot and work well in my .375 H&H.

I usually shoot Barnes, but might have to give the Accubond a tryout.