Penetration is perhaps the most important factor in selecting a new pistol calibre, or else we're quickly facing the reality that we'll need to shoot the enemy in the face to have any real chance at a kill shot.
Ok, but these troops getting armor - even the best penetrating pistol round available in a service type pistol, the 5.7, will NOT go through level 4 armor, or any of the plates/carrier systems being used now, and is only marginal at best vs soft armor 3a or better (
http://www.thefirearmblog.com/blog/2013/10/16/5-7x28mm-body-armor/). Like I said, the whole "harder hitting handgun" round thing is fellatios IMO, as even that argument, that future soldiers will be more armored doesn't matter when even rifle rounds will have a tough time penetrating - what hope does any pistol round have vs that? None really, for now with current tech being used. Penetration vs hard armor systems from a pistol velocity round is NOT going to happen, it just can't right now.
These nations aren't putting soft 3 or 3a armor on their troops, it's almost all in the 4 class, with ceramics and steel plates in use. Every year my company used to send me to the armor vs ammo thing that was held at the former Blackwater range. I've seen 5.7 shred cockpit doors and all sorts of soft armor, but the stuff like Paracleet, DragonScale, and the dozens of others that even small nations are putting on their troops - no pistol round, and few rifle rounds, are getting through that any longer. Even AP 308 will be stopped by even the cheaper ceramic plate systems now. This being the case, expecting a pistol to defeat it is impossible.
Don't get me wrong, 5.7 isn't a bad way to go IMO as it does give you the ability to get through other barriers that 9/45/40/etc can't, like lower class soft armor, other barriers like vehicle doors, and the like. Against well equipped enemy troops with the armor you're talking about G, it's just as ineffective as the above calibers.
I still think exploding ammo for small arms will be the future, and your armor point is part of the reason I believe this to be true. Standard rounds won't be very effective anymore due to the armor. Exploding rounds are another matter, they may not penetrate the plate systems, but the effects from the kaboom will deal damage all over the exposed body. I know there are treaties like I said, but nobody says boo when an AH64 kills swarms of Taliban with 30mm exploding ammo, do they. It's only a matter of time due to the race between armor and ammo that we end up going to really advanced projectiles that will either be able to get through the plates (less likely), or do enough blast damage that they don't really matter. It's already being worked on, a lot.
The data from Iraq and Afghanistan proves this out IMO. The number of troops killed by direct small arms enemy fire took a huge nose dive compared to past wars due to the armor systems being worn by many NATO troops. Many that were killed were by IED/blast weapons like VBEDS, IEDS, and RPGs, and other such things, not small arms rounds, and although it did happen, it was far, far less than previous fights as I said. Well, what is the west to do when the enemy starts wearing the same armor we are? That means our lethality from projectile small arms weapons is going to take a big nose dive as well, right? What is the solution to that - are we going to start using vbeds and ieds and rpgs as our primary way of killing the enemy? Unlikely. Explosive ammo is really the only solution short of some sort of directed energy weapon, or some wonder projectile that is fast and hard enough to bust through level 4 plates. Which is in the realm of the possible right now?
