For a sci-fi webcomic, I’ve been working on the specs of a class of power-armor clad enforcers (called Jotunns) and their weaponry; they have a specific handgun they use. For ammunition I was thinking of two types they carry: 12.7mm hollowpoint for soft targets and shorter range, and tungsten-tipped sabot rounds as ‘high-power’ rounds, for anti-armor/anti-giant-mutant and long-range use. Is this just me going way off the mark for firepower, or could this be justified for a man-scale tank?
So, 12.7mm is a real round (well, several different rounds), and it makes this entire question a little strange. We talked about the idiosyncrasies of firearms a couple weeks ago, and I had to check, but 12.7mm did come up as an example. 12.7mm is half an inch, so .50. Occasionally, you’ll see .50 BMG listed as 12.7x99mm instead of the imperial caliber.
I’ve seen 12.7 come up as a distinct round in, basically, two places. There’s a 12.7x108mm Chinese AM round, which is their answer to the .50 BMG, and, Fallout: New Vegas.
Ironically, the reason New Vegas calls it a 12.7mm is actually in the above paragraph. The game includes an Anti Materiel rifle patterned off the Barret which fires .50 BMG rounds. Because of how New Vegas formats ammunition names, this creates an immediate problem. There’s two different .50 rounds. The BMG and the AE. The AE is a handgun round (12.7x33mm), the BMG rifle round (again, 12.7x99mm). So, if you include a .50 pistol, and a .50 rifle, people who aren’t very firearms savvy are going to wonder why they don’t share ammunition. “I mean, it’s all .50, right?”
What Obsidian (I think this was specifically J.E. Sawyer’s call, but I’m not completely certain) chose to do was label one as 12.7mm, and the other one .50. Since the Barret has slightly more name recognition it got to keep the imperial name, and the pistol got the metric.
The other thing weighing on giving the pistol the metric name was, it’s a returning design from the first two Fallout games. They had something called a 14mm pistol (externally based on a SIG sporting pistol, if I’m remembering correctly), which was an upgrade from the .44 Desert Eagle, in game terms.
All of that said? .50AE isn’t a great round, and, while I could be wrong, I don’t see it having a real future. It fits with Fallout because it’s chromed steel excess meshes well with 1950s consumer design.
Hell, the Desert Eagle is an excellent example of that era’s design aesthetics. Big, heavy, more steel and chrome than is practical. It’s a four pound pistol. Even though it’s Israeli and didn’t actually enter production until the 1980s, it’s an excellent flash card for that era of Americana.
So, here’s the hard part. For someone who’s not wearing a powered exosuit, a .50 is an annoying round to control. In an exosuit, and against the kind of targets where you’d really need that kind of firepower, I’m inclined to think it would be kind of anemic. Why use a .50 round, when you could simply have a standardized 19mm or 25.4mm high explosive round? With varying payloads depending on what you’re shooting. Sure, no normal human could use it, but if you’re in powered armor, that’s not an issue.
A sabot round is, basically, a dart loaded into a shotgun shell. Now, that’s not completely accurate, but if you’re dead set on using one. I’d recommend just using solid darts, rather than having a distinct tip. For serious AP capability in a high power rifle, I’d actually be more inclined to point at man portable gauss weapons, rather than wasting space on a sabot.
All of this is going to be predicated on the technology your characters have access to. So, it’s possible your setting just doesn’t have portable gauss weapons. Also, feel free to ignore the bolter calibers I listed back up there. That is a Warhammer 40k reference. But, for ways to load out a suit of powered armor, 40k is a fantastic thing to look at.
Some quick primers for powered armor:
Starship Troopers by Robert Heinlein is probably the patient zero of SciFi space marines in powered armor. I deeply dislike the politics that Heinlein was advocating, but the book is worth reading. I’m much more partial to the film, but that’s a brutal takedown of the military jingoism that Heinlein was celebrating.
Armor by John Steakley is written as a rebuttal to Starship Troopers. I’m inclined to say it’s actually a better book, but that’s my bias seeping in. Either way, Steakley does some good worldbuilding.
If you haven’t, Warhammer 40k’s Space Marines are something you really should be looking at. You can check the Lexicanum to get a quick overview, and some basic statistical data; it will also work as a good quick litmus test to tell if the setting’s zealotry dialed to 11 and played for laughs is something you can actually get into and enjoy. For specific recommendations, first impulse here is to actually point at the THQ games. The generically titled Space Marine is a surprisingly good third person action title. Dawn of War was my first real introduction to the setting, and Dawn of War 2 specifically isn’t a bad starting point.
Generally speaking, when you’re looking at characters in powered armor, it can trace it’s lineage back through one of these sources. So it’s probably worth looking at them, if you’re working with this sub-genre.