Yeah, I'm here for rifles, so I won't get into the pistols. I will say, it's not the weight, or the speed necessarily. It's the construction of the 6 pedal 125 grain Gold Dot, made FOR the .357 SIG.
I was just dreaming of a .30-378 with a 1:9 or 1:8.5 barrel, slinging those 250 A-Tips.
Realize that back in the day that the 30x378 was most popular and most desired among PA long range hunters, there were very few powders offering full potential from the cartridge.
The best by far was WW2 surplus H570 followed by H870 which was in production up until about 10 years ago.
WC 872 also a surplus powder produces pretty much identical results as H870.
In my gun with a 36" barrel built on a Wolfe action, 113 gr of
H 570 produced 3500+ FPS with a 200 gr SMK.
118 gr of H870 would produce about the same velocity with the same bullet.
As for the BC factor, the 200 gr would out perform both the 220 SMK and the 240 SMK by a considerable amount as for elevation up to about 1500 yds with my gun.
In PA very few deer have been killed at 1500 yards or further.
In fact in 50 years of L/R hunting there i only know i man whose word I'd trust claiming a 1 mile kill. And the reason is conditions, not lack of guns or shooters.
For someone wanting to shoot that far and further, using the
Heavier bullets, by all means go to one of the larger 338s that will produce 3000 FPS or more with 300 gr bullets.
Yes you can get the 30 cal bullets out to the longer distances.
But you will do it better by way of accuracy with a 338 sending 300 gr bullets at 3200 + FPS.