I'm not aware of any .50 GI load that even approaches the sonic barrier. I'm also very skeptical of the terminal performance of any load which uses light-for-caliber bullets to achieve unusually high velocities. So far, every such creature exhibits poor penetration, often accompanied by bullet fragmentation.
The fastest production stuff that GI makes is the 185 CHP. I'm not sure I would personally want that much speed, but if I did, I could also get it from a 10mm conversion on the same Glock platform.
So, for your viewing pleasure, Brass Fetcher's YouTube channel has a 230 gr. copper hollow point ballistics gel video (same as the one posted by killoften).
https://www.youtube.com/watch?v=uO6GSRB-nQI
According to the video, the velocity was 1040 fps. Though it is certainly not the 1220 advertised for 124 gr. Gold Dot 9mm +P, or even the 1150 fps that Gold Dot 9mm is advertised to run, it is still pretty quick. In fact, Brass Fetcher's .45 ACP 230 gr. Gold Dot test put the velocity at 780 fps, and didn't quite make it out the other side of the gel block, but the .50 cal projectile didn't seem to have any trouble punching straight through. And for fifty caliber, 230 gr. would still be pretty light for caliber.
Another thing to keep in mind is that real-world wounds created by common service cartridges tend to be indistinguishable from one caliber to the next. A 9mm wound looks like a .40 S&W wound, which looks like a .45 ACP wound. It's not until you step it up into the full house .357 and 10mm range, where relatively heavy bullets can be driven very deeply when fully expanded, that things start to change (still nothing like rifle wounds, though). And the .043" difference between .357" bullets and 10mm bullets makes not a lick of difference, just as the .049 between .451 and .500 doesn't.
There are plenty of legitimate arguments to be made against the .50 GI, the most damning one is that most people don't really have much use for it. Like I said, it is too much like other popular rounds (9mm, .40 S&W, and .45 ACP); adequate in every respect, stellar in none. Every popular cartridge has some version of it that does things better: the .357 Sig is a barrel change away from a .40, and it is much faster than a 9mm; the .356 TSW could do anything a 9mm could do, and some of the things a .357 Sig could do, withought changing the 9mm's overall size; the 10mm is a far more bad-ass .40 S&W, and the .40 Super is practically magnum performance out of a standard frame gun; the .460 Rowland is to the .45 ACP what the .356 was to the 9mm. In any case, there is nothing spectacular about any of the highly popular defensive rounds. The same can be said about the .50 GI. Yes, the .50 could be faster, longer, meaner, etc. But that can be said about all cartridges. I still stand by my words that what makes the .50 so ripe for a place alongside the common semi-rounds is the very thing that will keep it from ever getting there; it is a very tame, sane sort of round.
All this, and then there's the issue of .50 GI reducing magazine capacity, on top of being (much) more expensive to shoot, and very difficult to find ammunition for other than online.
I understand the cost argument. I never hold that against a caliber. A knife costs significantly less to buy and practice with than a gun, but I'll stick with *pew-pew* over *stabby-stabby*. Maybe if the .50 GI came around in 1904, instead of 2004, we might all be using that... and if the .45 ACP was introduced in 2004, instead of 1904, we might all be wondering why some little company was trying to make a semi-automatic .45 caliber round that is only a little better than the old .45 Colt, but not as good as the .454 Casull.
But first comers do not always have staying power. The .41 AE comes to mind, as does its necked down variant, the 9mm AE. Most people have never heard of these, though they may own or shoot a .40 S&W or a .357 Sig. Now that we are 10 years in, this particular cartridge is obviously a niche cartridge. If it had had the backing of Smith and Wesson, Heckler & Koch, or Beretta or something, with Remington or Winchester making some affordable UMC/White Box versions, this round might have been okay. Even though it is not likely to gain popularity, there is always the possibility that a major manufacturer will come out with something like it that will be hailed as a game-changer, or even simply be tacitly accepted.
In any case, if any of you get the chance to shoot a .50 GI, it is plenty of fun.