PDWs...and other small arms.

[stanc]

6.5 Grendel with an M855A1 projectile does have arms defeat advantage over M855A1 5.56, and will perforate the CRISAT test at 400m from a 14.5" barrel.

That would be great if it was 30 years ago and we were planning to defeat the thin metal plate armor then in use by the Soviets.

But, how does it perform against current Russian ceramic armor?

A smart move would be to develop a PDW cartridge that is also suitable for a good portion of the Combat Arms Duty positions that are not specifically tasked with engaging the enemy with their primary weapon unless in the defense or in an overrun scenario. Guys like key leaders, RTOs, Ammo Bearers, Assistant Machine Gunners, Forward Observers, JTACs, TAC-Ps, Stinger Gunners, Javelin Gunners, Carl Gustav Gunners, etc.

None of them should be carrying a 9mm pistol. All of them should be carrying a small PDW that is effective out to 300m, but fits in a smaller package than 5.56 NATO, like the 6x35 KAC PDW updated with a better projectile in the form of M855A1.

If that 6x35 PDW was dusted off with engineered propellant, a higher BC, and copper core with steel penetrator construction, you could have something that would do as well as 5.56 NATO M855A1 by making up for MV with BC, while allowing many more magazines to be carried than is currently feasible. Even 5.56 mags become more difficult to carry with out armor. I used to be able to carry a double basic load before Interceptor IOTV and SAAPI plates. Now you have man units who go with an SOP that is less than the older 210 rounds basic load for the M16/M4.

With an improved 6x35 PDW, you could carry 1.5x as many mags as with NATO 5.56 STANAG mags, and have better terminal performance than M855, with higher hit probability than M855A1 5.56 by going with much higher BC.

Unfortunately, there appears to be a number of problems with your proposal.



1. The 6mm 65gr bullet has a lower BC than 5.56mm 62gr.

2. If the 6mm bullet construction is changed to steel tip/copper slug, projectile weight will decrease, and BC will be even lower.

3. In order to get your "much higher BC," it will be necessary to use a long-ogive bullet, a la 6.5 Grendel, which will increase cartridge OAL to that of 5.56 NATO, thereby permitting no reduction in magazine dimensions, or increase in number of magazines that can be carried. (Since OAL of the 6x35 TSWG cartridge is only 20% less than that of 5.56x45 NATO, I'm not sure how you figure it would be possible to fit 50% more magazines in the same area on a soldier's chest, anyway.)



4. Such a long, streamlined projectile would also be much heavier*, which would significantly reduce muzzle velocity, adversely affecting effective range and armor penetration.

*Steel core bullets for the 6mm Unified (below) were 77gr; for the 6mm SAW, 90gr.

Have a dismounted cartridge mix of:

PDW/Enhanced Infantry Rifle Cartridge for most soldiers
DM/Light SASS 6.5mm cartridge
6.5mm LSAT (which exceeds 7.62x54R performance)

These would replace the aging 9mm, 5.56 NATO, and 7.62 NATO systems and all their penalties and limitations. 9mm has no place outside the wire, 7.62 NATO is too heavy with not enough juice for the squeeze, and 5.56 suffers from too long of a case with no room for ogive length to increase BC like 5.45x39 has.

IMO, the optimum choice depends upon whether or not the capability to defeat modern hard body armor is wanted.

If it is, then I think it'll be necessary to use a cartridge which combines a high BC (hardened steel or tungsten core) projectile and very high muzzle velocity.

The velocity requirement pretty much calls for a return to long barrels. And the operational need for short weapons effectively mandates adoption of the bullpup concept.