The original 5.7 round was supposedly able to penetrate a NATO standard helmet at 80m and be pretty much nothing more than a bruise at 150mm.

The concept was to give the REMFs a weapon with lots of rounds in it that they could spray in relative safety because they weren't going to have to worry about killing their own side with wild fire.

So deadly when the bad guys over ran your rear echelons and got in close, but harmless at quite a short distance if said REMFs panicked and blasted fire all over the place.

So now the 5 and 7'' barrel .300BLK guns are all the rage or what  it seems French are looking for some.

They are looking for 5'' and 7'' barrel options in .300BLK for  Police and Gendarmerie

suppressor ,6 mags , M-lock interface on the forend

300K rounds of supersonic and 600k rounds of subsonic ammo

Modular construction enabling toolless conversion to 5.56mm

My impression is that the current crop of SBR (in the same caliber as the 'main' rifle), mated with modern ammunitions / suppressors / sights, are good enough for the PDW role.

For police spec ops, a suppressed 300 BLK 5" bbl is probably the most versatile configuration, with good enough accuracy and punch for <50 m, unless bad guys start using body armor en masse.

Ian just posted a new video.  The segment at 1:01-1:26 ( https://youtu.be/5Jx9DsbMqew?t=60 ) is interesting because it appears to imply that the Ukraine invasion validates the PDW concept. 

However, in all of the Ukraine vids and pics I've looked at, I have not seen any use of personal defense weapons like the H&K MP7, B&T MP9, or similar.  Has anyone else?

I’ve seen a number of Krinkovs (SBR class PDW) but none of the holsterable PDWs.

I do think the ATGM/RPG strategy does validate either the PDW or ‘light carbine’ concept. 

Namely, if your primary infantry roll is carrying and firing 14-50lb AT/ATGM/HE weapons, then you really want a light and compact firearm mostly for defense or close quarters ambush mopping up.

Something like Ian’s WWSD ultra light AR, as a 4.5lb carbine with 12.5” barrel and 7oz TA33 or Aimpoint T2 would be a compelling ATGM pairing.

gatnerd said:

I do think the ATGM/RPG strategy does validate either the PDW or ‘light carbine’ concept. 

Namely, if your primary infantry roll is carrying and firing 14-50lb AT/ATGM/HE weapons, then you really want a light and compact firearm mostly for defense or close quarters ambush mopping up.

Maybe I'm terribly mistaken, but I think no army considers "carrying and firing 14-50lb AT/ATGM/HE weapons" to be an infantryman's primary role.

Typically, an infantryman will be carrying only one of those 14-50 lb weapons, and once it has been fired, he reverts to his primary role of rifleman.

Which is why those soldiers are usually armed with the standard infantry rifle, not a holsterable PDW or ultra-lightweight, special purpose carbine.

P.S.  Where I did see some validation of the holsterable PDW concept is in the videos of Russian tanks which suffered catastrophic hits. 

Once the tank starts burning, the crew un-asses the vehicle muy pronto.  Any PDW not attached to their body is going to get left behind.

stancrist said:

Maybe I'm terribly mistaken, but I think no army considers "carrying and firing 14-50lb AT/ATGM/HE weapons" to be an infantryman's primary role.

You are propably right. The primary role of a German infantryman is to carry munitions for the squads MG and other heavy weapons... :P

What is an infantrymans main weapon depends on theatre, opposition, doctrine and tactic. IMHO it can be debated if mech infantrymen need rifles.
As can the infantrymans main asset in an environment with plenty of heavy weapons and AFVs.

stancrist said:

P.S. Where I did see some validation of the holsterable PDW concept is in the videos of Russian tanks which suffered catastrophic hits. Once the tank starts burning, the crew un-asses the vehicle muy pronto. Any PDW not attached to their body is going to get left behind.

Fully agree.
As a former tanker I have said this for a long time. AFV crews need a weapon that can stay conveniently attached to their body all the time. Otherwise the weapon will not be available if really needed. This is why I think a rifle or carbine is not suitable. To large to unwieldy. A PDW is the ideal choice.

stancrist said:

Maybe I'm terribly mistaken, but I think no army considers "carrying and firing 14-50lb AT/ATGM/HE weapons" to be an infantryman's primary role. Typically, an infantryman will be carrying only one of those 14-50 lb weapons, and once it has been fired, he reverts to his primary role of rifleman. Which is why those soldiers are usually armed with the standard infantry rifle, not a holsterable PDW or ultra-lightweight, special purpose carbine

I'd say its a new concept we're seeing developed right now by Ukraine; the Infantryman as primarily HE lobber rather then Rifleman or MG ammo bearer. 

But for David v Goliath conflicts (Ukraine/Tiny Baltics v Russia; Taiwan v China; Cyprus v Turkey; etc) I think this format is likely to be more developed. 

Namely, have a dispersed light infantry who cannot be easily spotted and targeted from the air, whose primary weapon is either an ATGM or MANPAD, and whose goal is to quickly inflict losses on an invading force before dispersing to fight another day. 

For those sort of states, I really think this is much more useful then traditional rifle/mg teams in the field trying to pin down forces for artillery and airstrikes 

...

In terms of 'whats the ideal sidearm for an ATGM/MANPAD' I dont think the Holsterable Class (MP7/MP9) is right, because as you mentioned once they fire their single shot they have to revert to rifleman. Holsterable makes more sense to me for a multi shot, reloadable weapon like the AT4 / Milkor.

I think exploring 'light carbine' PDWs may be worthwhile though for this role, with a goal of a 'ready to go' weight of 6lbs. This WWSD is a nice example of the concept, but obviously a more military tested option would be needed.