Take the 338 and the 375 with A-frames or North Forks and you can take virtually any animal on the
planet if you can shoot them well (exception is elephants without solids).
Most guides in Texas are full of BS and remember the best tracker in Texas is only slightly
better than Stevie Wonder!
I am not going to post the name of the guide here just because I have questions about his caliber and bullet advice. Why? Mainly because, while I may disagree with some of his advice, I also understand completely where he is coming from. He hosts dozens of out of town hunters every year. A majority if not most of them are NOT highly experienced hunters or expert marksmen. Many will be dentists or lawyers or other yahoos (you guys know who you are, lol) who do not have the time or inclination to practice at the range or become experts shooting off sticks at what is often longish ranges (for them) on game that is thick skinned and about as tough as a Blue Wildebeest. Even a good shot with a good bullet can lead to a tracking job of 50-100y in terrain that is sometimes thick with mesquite and other thick cover and as you said,
"Most guides in Texas are full of BS and remember the best tracker in Texas is only slightly better than Stevie Wonder!"
Hunting with a marginal marksman with a marginal rifle and making a poor shot leads to lost wounded game and unhappy clients who are not likely to recommend him to others. It is just good business to recommend the use of overkill rifles with very effective bullets to avoid all of that negative results. Who wants to track a wounded Nilgai who rarely leaves much of a blood trail anyway in the Gulf Coast Texas heat? His dislike of Barnes TSX bullets is likely because just like most copper monolithic bullets, they expand only a limited amount and do not dump energy fast like a lot of others but do penetrate well. While they almost always kill, they often do not do it as suddenly as say a bonded core like AccuBond or Scirocco for example. The prey will many times run for several seconds, and in the case of Texas, that is long enough to often get lost in the bushes and without a dog or a good tracker, that leaves it up to mostly luck if it is found.
In my case, I shoot well off sticks and spend loads of time with my rifles before I ever hunt with them and even with all that effort, I can muff a long shot if for example, my guide fails to accurately range a shot as I am setting up on the sticks. A 50y error can lead to a non-fatal first shot or a slowly fatal shot requiring a follow up. It happens. Using a high velocity round like the 300wm reduces the impact of such an error since the rifle will shoot flat out to a further range than say a 308 or 30-06 with a 180g slug. I get that. It is good insurance to make up for other client weaknesses. My preference is a bonded core bullet anyway if I can get one. They simply work well every time. They will expand to 2.4x at closer ranges and still penetrate very well.
I plan to take both the 375HH and the 338wm and I have 300g AccuBond ammo for the 375 and a variety of options for the 338 that I am still testing. I hope to limit my shots to 300y and less but will practice and plan for out to 400y if needed with the 338. Personally, I think you are far less likely to lose one if you shoot it from up closer just because you will be able to follow it visually better with less room for error after the shot. From the descriptions I have been getting the Nilgai are prone to running away as soon as they see you and they have keen eyesight. That reminds me of the Black Wildebeest I hunted in Free State on the open grass savannah this year. I had to shoot it at 314y.
While I have been to Africa a couple of times, I am mostly a Eastern woods hunter and we rarely shoot a deer at over 100y. In Africa the first time, my longest shots were 202y on a Gemsbok and 180y on a Blue WB. This year the long shots were 314y on the Blk WB, 280y on a Blesbok and 243y on a Springbok. All of these were with a 7mm/08 and all were successful. The guide says the Nilgai shots can be further. Thus, he asked us to bring flat shooting rifles that pack a punch.
My PH in Africa would let me hunt Eland with a 308 but our shots would all be less than 150y. There is a difference. It is not that the Nilgai is tougher, it is that the conditions force a tougher shot. Maybe on a different ranch the conditions would be better?
Recently, I was testing ammo and zeroing scopes on our two 338wm rifles. Mine is a Sako 85 that is coming around. I have gotten a few 1" groups out of it but more often they are closer to 1.5". A work in progress.
My son is a lefty and finding good left handed rifles is really tough. I lucked into a lightly used custom built on a modern Mauser left hand action with a Shaw match grade bbl in a McMillan Woody stock. The whole package makes a really nice hunting rifle and the Shaw bbl is living up to its reputation. The first three shots including the cold bore all fit inside of a 1.5" orange tgt dot and measures about 1" with Norma 230g Oryx ammo. The 2nd group was 225g Bartnes TTSX and was about 1.1" at 100y. All this with a 4x Burris fixed pwr optic that is not exactly Optimal for shooting tiny groups. Shaw is the easy button for precision marksmanship. My 375 wears one of their bbls also. My son is lucky I cannot shoot left handed or I might have kept this rifle, lol.
I think with a better scope it will be deadly.
Mauser Lefty 338wm Shaw bbl Game Slayer