stancrist said:

But I just don't see that happening with 7.5 FK BRNO, as it is too big and too powerful for use in service pistols. Which means that if the US Army were to field that 7.5 FK solution, they would be in the same situation as the German Army, with different calibers for the pistol and PDW.

The whole idea of a PDW is that it replaces the service pistol as well IMO. Otherwise not much use. It would just add another calibre. The PDW is not meant to be a small assault weapon, but something everybody carries who doesn't carry a rifle. Be that MP, tanker, truck driver or general.

schnuersi said:

I agree though that the chance for the US military to adopt the 7,5 or anything similar in concept is really 0. They seem to be entrenched on the 9 and 5,56 and all the other traditional calibers combination with the addition of the 6,8 in the near futur.

With good reason. If Elbonia wants to move from 9x18 and 7.62x39 to 7.5x27 and 6.8x51, that's a different story.

stancrist said:

It does not show that it is possible to design a modern military handgun for such a cartridge.

I disagree on that. A military sidearm differs by having mostly safety and controlls related rquirements. In additon to maintanance and ruggedness. There is nothing magical about it. If it a cartidge works form a pistol its possible to design a military pistol for it. The most simple way would be to just scale a current service pistol up or down.

stancrist said:

And I am arguing that it is not a realistically possible way, because it is extremely unlikely that any Western army would replace 9mm pistols with handguns chambered for a cartridge as powerful as 7.5 FK.

Ok, that is your opinion. But this is as good as mine. Because neither of us can predict the future. Who would have thought that the US would go for the 6,8 death ray a couple of years ago? Just as a possible scenario: if body armor penetration is getting the most important criteria there are little other options than cranking the power up.

stancrist said:

So, how would your purpose-designed, high ME cartridge differ from 7.5 FK?

That entirely depends on the exact requirements.
A somewhat lighter bullet but at higher speeds might be an option resulting in a 7 mm or 6,5 mm cartidge. The 7,5FK is optimised for raw KE and stopping power with deforming ammo. Which makes sense since its for hunting.
The cartidge also should become slimmer if at all possible.

stancrist said:

Bullet design is the problem. In gel testing the round nose bullet shows a late onset of yaw.

So the conclusion is: do not make the same mistake and use sub optimal bullet designs.

stancrist said:

How can I not "fixate" on the actual 7.5 FK when you constantly make statements like:

You have heard of the concepts of an example and extrapolation?

The possibility space for a PDW with magazine in grip configuration and a pistol using the same ammo now reaches from the 5,7 SCHV approach to the 7,5FK, as stand in for the high ME approach. Depending on the exact requirements it certainly is possible to find an optimum between these two.

Damnit

I had a more detailed post almost done then Delphi are it.

Short version of what I find baffling

1. Straight blowback actions are heavy stupid suppress badly compared to other options and suffer heavily in shoot ability compared to non blow back actions.

2. 9x19 is obsolete and anemic as hell while still managing to have more recoil than is actually desirable for both smg's and pistols

I know you'll come back with but 9mm is already in the supply chain etc etc to which I say yeah and how did that work out for the British and hanging onto the brown bess way past when technology etc had thoroughly passed it by?

I don't know if you've seen the most recent developments in 3a "soft armor" Stan but there's been some developments in the past few years that as soon as the Chicoms get the ability to produce it (expect them to be producing it within two years since somebody stupidly decided to let a Chinese armor vendor sell it under license about 18 months ago) the game will have thoroughly changed.

This soft armor is essentially a proprietary weave of your standard soft armor materials hot isostatic pressed at unholy pressures to essentially turn it into a very thin light and still flexible almost laminated format.

This stuff is good enough that you genuinely can't see if someone is wearing it concealed in a t shirt carrier or etc and has been demonstrated to eat HUNDREDS of rounds of 9mm 45 ACP etc at sub 7 yards and even point blank range without a single penetration. (Generally speaking in tests I've seen you're looking at 40 rounds before it starts penetrating into the second and third layers of the weave)

This is likely a problem.

Right now this armor is fairly expensive because there's not a whole lot of American manufacturing capacity to make it in large quantities...

China will not suffer from this handicap.

Having spoken to some people who work with the manufacturer, they say that with increased manufacturing capacity and availability the price of this stuff compared to normal 3a Panels to make is not that much more expensive.

That means this will proliferate.

Combine all of this and i think it's fair to say that it's not at all confusing why I find the army's choice of a straight blowback 9 subgun in the current years to be baffling.

As to your comment about there being plenty of m4's to use as pdw's, this I agree with you on in most respects however the army likes to spend money so we'll see.

The US military being so stuck on 9x19 is one of those things that genuinely sucks too since the cartridge is really showing it's age at this point.

5.56 OTOH... well if those idiots hadn't chosen the sig ammo for ngsw we would currently have the ultimate opportunity to do a 5.56 2.0 revision With true velocity neckless hybrid polycase that could probably take us another 50 years.

But again, idiots.

My sincere hope is that true velocity case technology and the company itself don't die out before the military realizes the grievous error it made in selecting the sig ammo concept.

graylion said:

The whole idea of a PDW is that it replaces the service pistol as well IMO.

Yes, the ideal PDW would also replace the service pistol.  The problem is, in order to do that, a PDW would have to be not much bigger or heavier than the service pistol.

Unfortunately, existing weapons made for this purpose -- like the HK MP7 and FN P90 -- are too bulky and heavy to replace all pistols in use throughout the armed forces.

graylion said:

Otherwise not much use. It would just add another calibre.

I disagree.  Adding another caliber to the inventory would complicate logistics, but it would not eliminate the usefulness of a PDW. 

History showed that with fielding during WWII of the M1 carbine, which added another caliber and was more useful than the pistol.

graylion said:

The PDW is not meant to be a small assault weapon, but something everybody carries who doesn't carry a rifle. Be that MP, tanker, truck driver or general.

If by small assault weapon you mean small assault rifle, there are differing views on that, depending upon how far the PDW user is expected to engage the enemy.

Does the PDW user only need to engage opponents out to ~100 meters, as some think?  Or should the PDW have effective range comparable to the enemy's rifles?

BTW,  military police and truck drivers don't really need a PDW, because in a combat zone they typically carry rifles.

Stan I think what many of us are suggesting here is outright replacing the obsolete 9x19 with something that's outright better.

We have ample demonstration that 9x19 Is actually obsolete... Wrote a post showing this in depth with super carry as an example but it got ate again.

I can go through it if you like but the tldr is that we can and should be doing something much better than 9x19.

schnuersi said:

       stancrist said: How can I not "fixate" on the actual 7.5 FK...

You have heard of the concepts of an example and extrapolation? The possibility space for a PDW with magazine in grip configuration and a pistol using the same ammo now reaches from the 5,7 SCHV approach to the 7,5FK, as stand in for the high ME approach.

I understand the concept of using an example, but I'm not sure that you do.

You used 7.5 FK as an example of a better PDW cartridge. 

But when I address the apparent drawbacks of 7.5 FK as a PDW cartridge, you object, saying that I am "fixated" on the very cartridge that you yourself argued for.

You can't have it both ways.  Either you are advocating 7.5 FK as a PDW cartridge, or you are not.  Which is it?

roguetechie said:

Stan I think what many of us are suggesting here is outright replacing the obsolete 9x19 with something that's outright better.

Yes, I understood that.  There doesn't seem to be agreement on what would be the best replacement, though.  The question is, what is better?

Some want an MP9 in 5.7 FN, while at least one wants a non-existent, MP7-style PDW in a non-existent, undefined cartridge of unknown caliber.

roguetechie said:

We have ample demonstration that 9x19 Is actually obsolete...

Is 9x19 truly obsolete, or does it just need a better bullet, like the change from M855 to M855A1?

I have some 9x19 FMJ ammo that gets 2000+ fps from a 4" barrel.  Perhaps something in that vein?

roguetechie said:

Wrote a post showing this in depth with super carry as an example but it got ate again.

Most unfortunate.  I had that problem with this forum a few years back. 

To counter it, I clicked on "Select All" and "Copy" before clicking on "Post".

That way when it ate my post, all I had to do was "Paste" the post again.

stancrist said:

Some want an MP9 in 5.7 FN, while at least one wants a non-existent, MP7-style PDW in a non-existent, undefined cartridge of unknown caliber.

The MP7 is too big IMO. It falls more into the 'light assault weapon' than in the 'sidearm' category.

For argument's sake I am using the 7.5x27, but something similar could be used - or with higher chamber pressure. 550 MPa should be doable.

So what do I want?

• MP9 kind of form factor
• powerful cartridge with high MV and light bullet
  • needs to fit into handle, otherwise gun will be too big for a sidearm
  • neck down 7.5x27 to 6.5?
• this needs a long barrel
  • so maybe the 'bullpup pistol' operating principle?
• reasonably precise at 100m
  • so fixed, not rotating barrel