It isn't that harmonics, BC, and MV have no effect, it's that there's no
practical effect on ballistic arc inside 300 yards. Harmonics affect group size, but once the bullet exits the crown, it's all aerodynamic efficiency and MV.
We are talking about 375H&H - I'm assuming a medium barrel profile of some sort, so heavy-ish.
With 2 loads, there are any number of opportunities to make a mistake and fill a magazine with the "wrong" one.
Another challenge presents itself - scope gets bumped off center during travels. As I mentioned in my hunting report this weekend, it ended up taking a dozen shots to re-zero my 9.3x62, and I'd only brought 30 rounds for it, leaving me with 18 to hunt for the week. Imagine that sort of issue and then having to re-zero 2 different loads, one of which was zeroed at 100 yards and the other at 200 yards. And now you're shooting metric distances at (probably) metric targets. That alone will introduce a little slop in the gears as well, likely negating the slight ballistic advantage he'd get from TTSX over A Frame anyway.
@375Fox - I would strongly encourage you to verify the loads at a range. Zero them both at 200 yards, I bet you'll find no more than 1" - 1.5" of ballistic arc difference out to around 250 yards, and no more than 2.5" - 3" at 300 yards.
I've done a similar test with my 6.5 Swede - 143 gr ELD-X (BC 0.625), MV 2500 vs 160 gr Weldcore (BC 0.51), MV 2380. I also did a SxS with my 308 (180 gr Grand Slam at 2550, BC 0.374) vs my 9.3x62 (286 gr Hornady SPRP at 2420, BC 0.41)
I also did the same test (though I didn't shoot out to 250 yards) with 286 gr A Frames (2475 fps, BC 0.385) and 258 gr Shock Hammers (2503 fps, BC 0.43) out to 100 yards, with a 150 yard zero.
My results were quite conclusive - zeroed for 200 yards, there is no meaningful difference in ballistic arc between the 2 loads for the Swede, nor was there a practical difference between the 9.3x62 and the 308 Win.
On a 200 yard zero, similar BCs (within roughly 0.1 of each other) launched at similar MVs (within 150 - 200 fps of each other) will produce very similar ballistic arcs out to around 300 yards.
I am a computer/math nerd, and
I just had to know if Hornady's ballistic calculator was reliable. I have always found that the margin for error on its calculated ballistic arc to be less than 1 MOA, usually less than 0.5 MOA. That's a big deal at 1000 yards, but it's just a non-starter at hunting distances.