stancrist said:

Yes, it was the same for me until a few years ago. Then I transitioned from searching for the ideal, to looking at what seems more realistic.

I have given up on this quite some time ago. What is realistic is at best boring, most of the time borderline stupid and sadly not seldom outright disgusting.
What is happening with the restructuring of the German Army currently is such a case. Somthing boring but sensible has been promissed. What we get is outright disgusting and retarded. Its just aggravating and tiring.

Thinking about ideals at least is fun.

stancrist said:

However, if 6.8 works really well, I could see it possibly replacing both 5.56 and 7.62 completely.

I agree. But it will most likely take a couple of decades. Several NATO countries are currently in the process or planning to adopt new 5,56 and 7,62 weapons. At best in the next round of replacements the transition to 6.8 will be done. But since arguments like the ones you brough up some posts ago will be made, simplified "its cheaper to stick with what we have", there will be a serious reluctance to change until the business case can be made that transitioning is cheaper. The problematic part is that governmental agencies and especially politicians only think in chash flow not in investment. This can make it very hard to argue for "it will be cheaper in the long run".

stancrist said:

And I fully agree that 9x19 is here to stay, if only because the pistol is universally considered necessary and nobody wants a 4.6 or 5.7 handgun.

And this is a case of outright stupidity IMHO.

4.6 might not work well from a pistol. Allthough I would argue that in a properly designed pistol for 4,6 and not just a conversion of a 9x19 it would work. Never the less 5.7 does work from pistols. It is proven and effective. So one could argue that if pistol use is really a necessity (which I doubt) the adoption of 5,7 would allow to replace 9x19. This in turn would really simplify logistic and save resources in the long run because this would allow to phase 9x19 out and transition lots of 5,56 users to 5.7.

gatnerd said:

As I've said numerous times, and echoing Tony's comments, where the PDW makes the most sense is for the 'HE lobber.' A infantry guy whose primary job is employing man portable HE weapons (40mm smart grenades, 84mm CG, ATGMs, MANPADS, etc.)

The important part here is "infantry guy". Yes he might need a PDW. But since he is infantry his needs don't really overlap with all the other potential PDWs users who are not infantry.
IMHO it really makes little sense to use the same PDW class weapon for the infantry users and everybody else. For example for the infantry users caliber comonality with the rest of the squad is a serious advantage. The training and mode of operation also would allow the infantry user to actially make use of the potential of 5,56. So a SBR of some sort of 5,56 PDW make sense for these guys. But it needs to be kept in mind that they are few in comparison. A special case.
To me it seems not the ideal solution to try and shoehorn a single solution based on the needs of a special few for everyone. This will ultimately lead to a similar situation as we currently have.
This is why I am advocating the infantry weapons for infantry and a PDW with focus on easy of carrying and use for anybody else.

gatnerd said:

For truck drivers / mechanics / cooks etc (the original use case of the PDW) I dont think its worth the hassle vs just issuing them a M4 or a pistol, as their probability of conflict is so low.

And if their propability of conflict is so low why should they carry unnecessarily powerfull and large (carbine) or allmost useless (pistol) weapons? The thing is if these occupations have to use their small arms something went wrong allready. So they need something that works best for them in such a situation.
The statement that the propability of conflict is low also seems questionable. The losses of the German Army in Afghanistan include a disproportionate number of non infantry and even non combat personel. This might be a theatre specific problem but IMHO theatres similar to Afghanistan are more likely in the future for the German Army and all NATO Armies. Regardless what is happening currently and all the politicians chiming about homeland defense. Once the situation in UA is solved other things will come back into focus. The world has not become a saver place. UN and NATO missions in LIC and COIN scenarios are still very likely. Even though we might not like it or want it.

gatnerd said:

As I've said numerous times, and echoing Tony's comments, where the PDW makes the most sense is for the 'HE lobber.' A infantry guy whose primary job is employing man portable HE weapons (40mm smart grenades, 84mm CG, ATGMs, MANPADS, etc.)

I have to disagree.  I think that a PDW of the types you propose for the "HE lobber" make little sense.

Weight of loaded MP9 + 3 spare mags is ~7 lbs.  A loaded CMMG + 3 extra mags would be over 8 lbs.

Note that in your examples the Ranger carried a pistol (weight penalty ~ 3.5 lbs) and the XM25 users didn't carry a secondary weapon.

The "HE lobbers" operate as part of a team, and their focus should be on maximizing effectiveness with their primary weapon systems,

As Tony said, the heavier is the secondary weapon, the less weight is available for grenades, so the less effective the grenadier will be.

IMO, a pistol is the best choice of secondary arm for troops equipped with multi-shot grenade launchers and the reloadable 84mm CG.

And "HE lobbers" with a disposable weapon like AT4 and Javelin, really should have a carbine/rifle for use after expending their missile.

PDWU? Personal Defense Weapon Upper, 11.5" barrel, with suppressor taking it out to 14.5". Figure to use an integral suppressor to keep length down.

Farmplinker said:

11.5" barrel, with suppressor taking it out to 14.5"

OMG, it feels like deja vu all over again!    

I always considered the XM177 to be the best looking M16 variant.  

schnuersi said:

       gatnerd said: For truck drivers / mechanics / cooks etc (the original use case of the PDW) I dont think its worth the hassle vs just issuing them a M4 or a pistol, as their probability of conflict is so low.

The statement that the propability of conflict is low also seems questionable. The losses of the German Army in Afghanistan include a disproportionate number of non infantry and even non combat personel. This might be a theatre specific problem but IMHO theatres similar to Afghanistan are more likely in the future for the German Army and all NATO Armies.

In order to propose a solution, we first need to know what the problem is. 

What caused those losses:  IED blasts?  Enemy fire?  Green on blue attacks?

Such information could make a big difference in what type of "PDW" is best.

And with planning for (near) peer war, PDW needs may differ from LIC/COIN.

stancrist said:

What caused those losses: IED blasts? Enemy fire? Green on blue attacks?

You are right. So I looked it up. Only superficially though.
The total losses of the Germany troops in Afghanistan are 59 KIA. The vast majority are by IED/suicide bombers. Losses to enemy fire are rather few. I counted six due to enemy fire. Three by accident during a firefight. Three by green on blue.
The green on blue have been two AFV crew and one mechanic. Shot while performing repairs and maintenance on a IFV inside the base.

stancrist said:

And with planning for (near) peer war, PDW needs may differ from LIC/COIN.

I am not really convinced it is. While LIC/COIN or HIC has conciderable influence on how infantry operates and what their engagement ranges are I don't really think this is the case with PDW use by non infantry personel. In either case we talk about self defense to maybe 100 m.
The target might make a difference but 5.7 and 4.6 have been designed with near pear HIC in mind so they will most likely work as intended in such a scenario. For LIC/COIN their single shot stopping power might be insufficient and their penetration to good so they are not the optimal choice. I really think it comes down to ammo used though. 

schnuersi said:

The green on blue have been two AFV crew and one mechanic. Shot while performing repairs and maintenance on a IFV inside the base.

No MP7 available?

EmericD said:

No MP7 available?

While performing repairs and maintenance on the vehicle, the mechanic and crewmen were almost certainly unarmed.

Even in the unlikely event each had an MP7 on his body, it would not have mattered because their focus was on the job.

EmericD said:

No MP7 available?

Apparently not. I don't even know if they where equiped with MP7.