However, I recall reading in Infantry magazine back around 2004-2006, that the US Army had opted for a 10.5" barrel version of the M4A1 carbine for the personal defense requirement. (See attached photo of such a weapon being carried by a senior non-com in late 2007.)
Since Variable has been shooting a similar short-barrel carbine in 6.5 Grendel for some time, it would seem like a suitable option for a military PDW.
One of the challenges of the short barrel and standard ammunition is that the muzzle blast gets to be horrific due to high muzzle pressures and the muzzle being that much closer to the shooter's ear. The problem gets to be particularly acute when shooting from confined spaces.
I ran a QuickLoad exercise on this topic a few months back and discovered that it is possible to get muzzle velocities within a couple of hundred feet per second of standard ammuntion in a 7.5 inch(!) barrel with lighter loads of pistol powder and have a muzzle pressure that's only 10 percent higher than one would see with the 14.5" M4.
Naturally, this second ammunition type would need to be optimized to assure reliable function in the weapon so that standard-issue ammunition could be used in an emergency.
Since the introduction of the FN P90, a new breed of ammunition suitable for PDW use has emerged, that being governed by the parameters of 1) being able to fit within a pistol frame, as the P90 and FN Five-Seven, the new Russian rounds, the Chinese 5.8 PDW cartridge, etc. while 2) pushing velocities closer to the rifle spectrum. I have been a big fan of the 7.62x25 in that respect, and the 6.5x25 seems even more promising with regards to velocities from a pistol-size cartridge.
The Grendel seems pretty overkill for a PDW since 5.56 NATO is considered such already, hence the KAC 6x35 PDW. Another major selling point and trend that PDW's have gone directionally is ammunition capacity per weight and more importantly: space. Unfortunately, the Grendel moves in the opposite direction from those parameters.
The possible solutions for a Grendel PDW would involve a lightweight projectile, and some type of unconventional magazine with a quad-stack fed into a dual stack like the Surefire and Magpul mags that are being introduced currently. The brass weight would still be an issue compared to other modern PDW cartridges, but the Grendel would of course offer better effective range than any PDW I can think of. Combined with an improved recoil system, these features would help mitigate the penalties of a larger cartridge under the universal caliber concept, if that's what one is looking for.
As I have already stated, I lean towards caliber-specific roles to enhance the system in its function, rather than trying to fit one niche caliber to a role that isn't ideal. In the PDW role, I would want maximum ammunition in the most concealable space profile, with suitable wound and penetrative capacity within 100m. That would include the ability to shoot through vehicle structures from within the vehicle compartment, and some type of noise suppression option for plainclothes work.
Better yet, load that armor-piercing sabot round (6.5X25CBJ) in the Grendel!
Same exercise as in Post #2 should get a few hundred feet per second better in that short barrel than even for the long-barrel version of the pistol caliber and still have muzzle blast at tolerable levels.
That 10.25" barrel CQBR upper is a SOCOM project that is meant to reduce the M4 profile for Close Quarter Battle, especially when used with a suppressor. If you look at the shoulder patch of the dude in the picture carrying the CQBR upper-equipped M4, it says it all.
That gas system and barrel length are more problematic with the AR15, even with a gas port diameter of .093". I have a friend who's waiting on a broken shell extractor right now for his. The Army learned this back in the 1960's with the 10" barreled XM177E1, before increasing the barrel length to 11.5" on the XM177E2, as well as using the moderator with baffles to increase back pressure on the gas system to help with dwell time & reliability. The funny thing is that an XM177E2 has about the same length as a 14.5" barrel, when the length of the moderator is included.
I've owned at least 3 different AR15's with 11.5" barrels, and never had a hiccup with them that I can remember. For a PDW, I would think of a physical profile objective of being a great under-the-coat gun.
I much prefer the MP9 as a PDW, regardless of whether it's in 6.5x25 or 9x19, but a 10.5-inch M4 is what I recall the Infantry School commandant said was going to be the Army's near term PDW.
With that in mind, 6.5 Grendel could be used in a PDW, carbine, DMR/light sniper rifle, IAR, and (if suitable links can be designed) belt-fed LMG.
Tony,
I enjoyed your article on PDW's. I've always been a fan of the Steyr TMP. I stumbled across a "new" platform that I thought might meet the requirements of a PDW. Are you familiar with Rock Rivers Piston Driven System?
What I believe sets this gun apart is that since it is a piston sytem, there is no need for a stock and buffer. So, it can be equipped with a folding stock making it very compact. But, as your article mentions, the 5.56 is overkill for the role. What if this gun was chambered in one of the other calibers you mentioned or (my personal favorite) .45ACP. And, if you wanted more of a rifle round, make it a .50 Beo or .458S or .450Bush or whatever. What would you have then? A guaranteed stopper out to 200 yards in a gun less than 18" (folded).
Well, the Beo, .458, and .450 are all surely fight stoppers out to 200, but carrying ammo for them is not exactly comfortable. Remember, only 10 rounds to a mag, so even 10 mags only gets you 100 rounds of ammo!
BUT...boy do they make people drop what they are doing and come look!
I suspect that if you were clearing a room, the first couple shots would make everyone there rethink their options!
You seek escape from pain. We seek the achievement of happiness. You exist for the sake of avoiding punishment. We exist for the sake of earning rewards. Threats will not make us function; fear is not our incentive. It is not death that we wish to avoid, but life that we wish to live. - John Galt
The problem with the bigger calibers though is if you had to take a shot in a crowd, you're going to end up going through into something you don't want to hit. It's hard to beat an MP5-K or MP-9 for this kind of role.
If I was going for a conventional carbine layout, then the KAC PDW in 6x35 would be my choice.
If I had to use 5.56mm, then the Magpul PDR looks the most promising.
The .45's rainbow trajectory at long range really rules it out of consideration for a compact, lightweight PDR. As does the ammo size and weight. And the recoil's effect on controllability in burst fire.
Incidentally, I've just revamped my PDW article, as of yesterday afternoon - including making sure that all the links work!
Quote:ok, so big calibers aside, you guys like that setup for a PDW? Is 45ACP enough out to 200?
.45 ACP is a NO-GO as far as PDW cartridges are concerned, and not really much of a viable cartridge for standard military sidearms anymore. One of the key parameters of a PDW is firepower, and being able to pack as much firepower in a lightweight and low-profile package. Once you start to carry .45 ACP in large quantities, you realize quickly that it fails horribly in this regard. .45 ACP is nowhere near a 200m cartridge...try 50m.
Bottle-necked cartridges are what dominate the last 2 decades of PDW developments, both in the East and Europe.
LRRPF52 Wrote:....Once you start to carry .45 ACP in large quantities, you realize quickly that it fails horribly in this regard.
It's amazing how much our perspective changes with time. During most of the 3/4 century the cartridge was our standard sidearm, the 30-06 was the rifleman's cartridge. That fat pill was light compared to the good ole '06.
Quote:...45 ACP is nowhere near a 200m cartridge...try 50m.
I think you are over-optimistic when you consider the standard trigger pull, sights, and training. The folks who carried it were for the most part inadequately trained in how to use the pistol. Hence they were frequently as afraid of the pistol as they were the adversary they were shooting at!
Try 15 meters for the average soldier and, as much as 125 meters for a tuned pistol in the hands of a skilled marksman.
Point is, you are right on target regarding the bottom line. As much as I love the .45, there are better choices -- I will admit that the 6.5X25 gets my attention, but don't know if we're there yet!
JASmith Wrote:I think you are over-optimistic when you consider the standard trigger pull, sights, and training. The folks who carried it were for the most part inadequately trained in how to use the pistol. Hence they were frequently as afraid of the pistol as they were the adversary they were shooting at!
Try 15 meters for the average soldier and, as much as 125 meters for a tuned pistol in the hands of a skilled marksman.
I think that the reference to 50m might have been in the context of a stocked PDW like the B&T MP9 (which has recently been developed in .45 calibre).
Tony Williams Wrote:I think that the reference to 50m might have been in the context of a stocked PDW like the B&T MP9 (which has recently been developed in .45 calibre).
You're right, I had neglected the Tommy Gun!
That one had a lot of advanges -- shoulder fired, good sight radius, and a barrel length that gave the .45 a solid velocity boost. It would indeed do well at 50 meters.
{Don't even want to start talking about the M-1 carbine...}
Also, I am having a hard time adjusting to the notion that the PDW is primarily an ultra-compact carbine that can, in an emergency, be used as a classic pistol. This change in use pattern will also impact preferred sight systems and cartridge optimization.
LRRPF52 Wrote:.45 ACP is a NO-GO as far as PDW cartridges are concerned, and not really much of a viable cartridge for standard military sidearms anymore. One of the key parameters of a PDW is firepower, and being able to pack as much firepower in a lightweight and low-profile package. Once you start to carry .45 ACP in large quantities, you realize quickly that it fails horribly in this regard. .45 ACP is nowhere near a 200m cartridge...try 50m.
I concur with all but the last sentence. A .45 PDW ought to be capable of hitting a man at much longer than 50 meters distance. Some friends of mine and I one day were plinking at rocks on a hillside about 400 yards away, with a .45-cal Reising SMG. Shooting semi-auto, it was fairly easy to kick up dust within a foot or two of the rocks, and that with the simple open sights.
Yes, the .45 ACP/50m effective range reference was from an SMG. Those big, fat 230gr FMJ's have hardly any penetration power as the distance increases as well. One cartridge that I really love that fits the PDW role extremely well is the 7.62x25. I've been wanting to build a 1911 in that cartridge for a while, but sourcing a mag for the 1911 frame that will fit the Tokarev cartridge's COAL is futile. There is a company offering a 1911 barrel chambered in 7.62x25, but it is non-ramped.
A highly-gifted gunsmith I know in North Carolina built an AR15 chambered in this cartridge. He used a blank lower forging, and broached the magwell to take Soviet PPS mags. He cut the rest of the lower to spec, and cut mag catch holes in the PPS mags so they would lock into the lower a la AR15 fashion. He made a barrel bushing for a PPSh pipe so it would slip into the upper, and you just hand-screwed a carbon fiber handguard onto it. A 9mm SMG bolt and SMG heavy buffer completed the rig. He baked-on some proprietary DuPont metal surface finish meant for chemical pipes, and it turned out really sweet. It would blow right through 1/4" steel plates within 25m.
I have done side-by-side comparisons of 9mm, .45 ACP, and 7.62x25 on a Finnish Army steel drum from WWII that was in need of being used as a burn barrel. The 9mm and .45 bounced off it repeatedly. The Cz52 chambered in 7.62x25 shot through one end and out the other, even when I shot deflecting aspect shots.
I also have friends who have shot amazing groups with a Tokarev or Cz52 pistol at 200m with iron sights. You used to be able to get a 1220rd case of it for $129, but I can't seem to find that anymore...word must have gotten out.
My PDW is a 1947 Soviet TT-33, like others I have found that the 7.62x25 will shoot through things I never though it would. And it is accurate enough that I can hit a man sized target at 100yds. Yes the surplus ammo is getting harder to find, and most that is around right now is Polish sub-gun ammo so it really isn't ok to shoot in a TT-33, but would be fine out of a CZ52.
