I just realized
my post from the NGSW thread wasn't moved over here, so let me copy it over and make my point about 5.56.
TL;DR: 5.56x45mm is a nearly perfect balance of low logistical and soldier load footprint, high lethality, accuracy, and low recoil.
It also has a significant amount of growth opportunity to improve on these strengths by implementing existing concepts like lightweight high pressure cases (such as the
NAS3 steel case or True Velocity polymer case) which would drop weight by ~1/3 (from 12 grams per cartridge to 8 grams) while readily allowing muzzle velocities in excess of 3250 ft/s from 14.5"-16" barrels, and
neckless case geometries to allow a more aerodynamic bullet without needing to modify the rifle. Of course, bringing all this together would take time, money and testing, but you're looking at gluing a bunch of TRL-6 to 9 concepts together.
There's absolutely no way that rifle fire is killing more people in Ukraine than explosives (be it hand grenades, artillery, kamikaze drones, mines, bombs, missiles, rockets, ATGW, etc).
Small arms (including the MG) still kill, but the trend has been incredibly stable that in conventional wars they produce ~10-30% of casualties, with the majority of lethality and casualty production coming from explosive weapons (artillery, aircraft, grenades, mines). The exact balances change over time, but if you're looking at the numbers then improving infantry lethality is going to come from enabling fires, fixing the explosive shortage, and improving the ability of small units to throw HE-FRAG at the enemy (commando mortars, FPVs, kamikaze drones, a gustav that doesn't give you brain damage, using one of those tennis ball throwers for dogs to chuck hand grenades), NOT from adopting a battle rifle.
Spending >400,000,000 a year on NGSW is (IMO) pretty symptomatic of how much the Army has lost the path on infantry, in part due to the over-emphasis on light infantry and airborne. The baffling part is that 6.8x51 ammunition is nearly twice as heavy as 5.56, at ~22g vs ~12g, so even if the gun weight is held steady the infantry basic load of 210 5.56 rounds (2.5kg) either goes up to 4.6kg for 210 rounds of 6.8 or stays at 2.5kg but only gets you ~114 rounds of 6.8.
Breaking the ammunition weight out a little further, you've got:
View attachment 811201
Apologies for the inconsistent numbers, I put 21.7 into the spreadsheet instead of 22g. Generously there's a version of the squad comparison where 6.8 saves weight vs 5.56, but it saves 3.4kg per squad in exchange for carrying 2000 fewer rounds of ammunition, equivalent to both 5.56 SAW gunners! And that 3.4kg is only equivalent to 286rds 5.56/158rds 6.8!
The ammunition weight issue is unsolvable for 6.8x51, and IMO is the most lethal problem, to the program and to the infantry that have to carry it. It's a recipe to lose the volume of fire fight and have sustainment issues in the field.
Of course there's also the looming alternative that SOCOM is moving towards: high pressure 5.56x45. There's been some scuttlebutt of pushing 62 grain projectiles (i.e. M855/A1) at ~3180 ft/s (970m/s) out of an 11" barrel. That's scratching M193 20" muzzle velocities, probably faster out of a 14.5" barrel (i.e. standard infantry rifle). Flatter shooting, longer effective range, plenty of lethality, backwards compatible, no weight increase, and relatively inexpensive. NAS3 cases even are a ~4g per casing weight SAVINGS, which is 840-1320g per rifleman and 2400-4000g per SAW gunner just from a better case design.
So of course, in true Army fashion, they're spending a lot of money on fundamentally flawed rifles instead of doing the less expensive and better performing route. Just like cancelling JLTV for what is essentially the bastard child of a CUCV and the fabric roof HMMWV, because it's a great idea to get rid of shrapnel protection when battlefields are coming to be dominated by artillery and ATGW (including FPV/Kamikaze drones).
I am constantly baffled how they managed to avoid significant scrutiny, and I really wish that the Army would be hauled in front of congress and asked to answer how they made this math work.
IMO the cost argument falls apart when you have to buy new receivers. NAS3 cases have more internal volume so it's possible a longer bullet could fit to get better ballistics in a 62 grain projectile. Personally I think that the steel case should be a fairly large warning that it'll blow up guns. There's also the prospect of mixing NAS3 with the neckless geometries of 5.56 that TV and some people online have played with to get the longer bullet in the same OAL. I've heard some scuttlebutt that steel has odd neck tension issues that might preclude this, but the general point is that 5.56x45's formfactor is absolutely not pushed to the limit, and there's room for a rebarrel/bolt upgrade that should make 5.56 shoot absurdly flat and punch through velocity limited plates (which is most ceramics and steel) at reasonable ranges.
A while back I sketched out a concept for 3300 ft/s 62gr with the G7 of 7N6 (.168) which ended up being comically flat shooting (a 300-350m battle zero ends up mathing out to fairly point and shoot to 500m.
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