I can't remember the actual yards that canadian sniper fired to kill that guy, but it was impressive, something around 1700 yards or near a mile IIRC, but not exactly 1760 yards. Not only that, but the 50 had enough snuf to penetrate light armor and killed the guy behind it! WOW, that 50 is impressive! LOL! I read about that shot in a magazine and then they were talking about it on a show on the military channel the other day called "Weaponry" or something like that, all about modern weapons and development. The guy that narrates it is an ex-seal sniper.
I doubt that many calibers effective range would be determined by where it goes sub sonic because that point it's falling like a rock. My 22, would probably be pretty impressive at 200, but I don't think I have enough adjustment in the scope I have on it, ROFL!!!! We have a 200 yard range and I fire on it from time to time even with my Contender pistol, but I've not tried to shoot a rimfire down there, just seems like an exercise in futility. Not only is the trajectory a rainbow, but wind drift is aweful on a .22 if there's any wind at all. The times I've fired at 300 was from the gate down to the 200 yard target boards and no one else was at the range. Now days, don't get to do that much cause the club has a lot of members now and the range is rarely vacant, but that's a good thing for the club, I guess.
So, what I use my ballistics for when I develop a load is mainly to assure me that it has enough energy to X yards to do the job and to know where to set it at 100 for maximum point blank range. I generally use a 3" maximum point blank range for deer and hogs on my rifles. Generally, there ain't a lot of difference from caliber to caliber in the better rifle calibers, though, and unless I go out west, the exercise is moot cause I can't see past 200 yards in the brush from my deer stands on my place, LOL! However, having a good knowledge of your rifle, especially spot and stalking mulies out in New Mexico's arid mountains, is a good thing. My personal limit for hunting is 400 yards and my programs do a decent job of prediction to that range and more. I know there are those who brag about 600 yard shots on the various boards and good on 'em, but I don't have the facilities to do that kind of shooting and the variables, like wind drift and up or down hill incline, are too much for me to be trying that long a shot even if I lase the range and know the bullet drop. So, my limits are self imposed. There's more to consider than just drop or velocity induced accuracy losses, which on a .308 or 7mm Rem Mag or even my .257 Roberts is going to be well above sonic as you pointed out earlier. Even if in some way, you loose a little bit of accuracy from SOME rounds with SOME twist rates, okay, I can see that, it won't affect me and my shooting, so it's moot for all practical purposes, at least for me and what I do with a firearm.