That time of the year again - Army seeks improved carbine

[Stark]

The answer to '9mm sucks' is not 'lol overload 9mm'. If I had a dollar for every time you've said '+P+' this week I'd be... less hungry.

[JointStrikeFighter]

Russian 9mm +P+ rounds are so different from normal 9*19mm parabellum that they might as wekk be a different round anyway.

The russians also have 9*21 as an option

[Stark]

So by '+P+' your current favourite buzzword you actually mean 'a totally different round'? Clever! Or maybe you didn't know people have been using overloaded 9x19 for decades?

If you wanted to say 'just use the Bizon' just... say that.

[JointStrikeFighter]

Just use the Grach :V

Ruski AP 9mm +P+ rounds supposedly get the same prentration as the PDW subcalibres and arguably the bigger wound channel means more lethality.

[Stark]

You forgot to say 'hydrostatic'. The Grach is a 9x19 pistol.

[JointStrikeFighter]

an armour piercing 9mm pistol

[Stark]

I think you mean 'armour piercing'.

[JointStrikeFighter]

Alpha Papa Pistol Ammountion

[His Divine Shadow]

Oh no the australians turned upon each other. Too much snark can be a dangerous thing.

[Edward Yee]

If SMGs weren't married to 9mm they'd be more competitive, but changing rifle round would have the same effect. In many ways the weapons are identical these days anyway, and an AP round the handles short barrels better would make it irrelevant.

*Looks at the UMP40 and UMP45* There was also a MP5/10 (erroneously called "MP10" in the Rainbow Six novel) and MP5/40, though I understand that H&K stopped making them.

Also, regarding the HK53 -- wasn't that was an early (relative to now) short-barreled rifle also in 5.56x45mm? I fail to see how it'd be much better than the modern 5.56x45mm SBRs in terminal ballistics. I will note though that KAC's 6x35mm caliber was supposed to be used in this role, and that may have been one of the goals of 6.8x43 (to outperform 5.56x45 and 7.62x51 at least in a SBR, considering that those are its "comparison" calibers).

Personally I (and probably more) had a soft spot for Magpul's "Personal Defense Rifle" project, but Magpul at the moment is mum; supposedly it's still in the "concept" phase, but maybe a year ago a Magpul rep on ARFCOM admitted that the US military hadn't so much as called back when they proposed the PDR, thus deprioritizing the project within Magpul.

Heh at the MP7 mention -- the fact that it can have both pistol and SMG-like aspects (at least, the collapsible stock and fold-down foregrip) don't make it less confusing, though in general I lean towards calling it a machine pistol, and the P90? SMG.

[Elfdart]

So... you agree that 9mm and 5.56 in a short barrel are both poor choices and that other rounds will be developed, then? They whole concept of 'small rifle' and 'powerful SMG' being different is simply an accident of ammunition, which is the whole reason intermediate rounds are now being developed and things like the HK53 have existed for years..

And sorry, a 10mm (or whatever) SMG would be much better against body armour than a 9mm.

Bring back the Thompson. Problem solved.

[His Divine Shadow]

Do you know something I don't about .45ACP? Because it's armor piercing properties are inferior to even 9mm. It's a slow heavy bullet, not really qualities suited for AP work.

[CaptHawkeye]

Bring back the Thompson. Problem solved.

The UMP basically is Thompson 2.0

That being said I still get my jollies from seeing old war guns tacticooled up. I feel like seeing a Mosin Nagant with ACOG today.

[Marcus Aurelius]

If SMGs weren't married to 9mm they'd be more competitive, but changing rifle round would have the same effect. In many ways the weapons are identical these days anyway, and an AP round the handles short barrels better would make it irrelevant.

*Looks at the UMP40 and UMP45* There was also a MP5/10 (erroneously called "MP10" in the Rainbow Six novel) and MP5/40, though I understand that H&K stopped making them.

The .40 S&W cartridge is a feelgood round for Americans, who like the idea of packing something more powerful and American than the 9x19 mm Para. In practice the difference is minimal, especially if we talk about FMJ. With expanding bullets the difference might be borderline significant, but since the hydrostatic shock effect is still more like a hypothesis than a proper theory, I would not get overly exited about that either. For military use expanding bullets are irrelevant in any case. The .40 S&W also has no penetration advantage over 9x19 mm, unlike 10 mm Auto.

10 mm Auto on the other hand is a pretty good SMG cartridge, although it doesn't have any penetration advantage over +P+ 9 mm, either. So all in all the good old 9x19 mm is still one of the best, if not the best traditional SMG cartridge. 7.62x25 mm Tokarev has potentially better penetration, but suffers at least mentally from its small diameter for a pistol round, and of course there has been very little active development of new weapons for it after the 1940s.

Heh at the MP7 mention -- the fact that it can have both pistol and SMG-like aspects (at least, the collapsible stock and fold-down foregrip) don't make it less confusing, though in general I lean towards calling it a machine pistol, and the P90? SMG.

In German it of course is a machine pistol, but then again any full auto weapon firing a pistol cartridge is a machine pistol in German. Evidently H&K felt that the MP7 is close enough to that definition despite the novel cartridge. In English the term is usually used for full auto weapons which are primarily used without a forward grip or shoulder stock, but I doubt the MP7 gets used that way too much, so I would call it an SMG as well. That is, if we accept that the traditional definition of a SMG is obsolescent due to these newfangled cartridges.

Bring back the Thompson. Problem solved.

.45 ACP is one of the poorest cartridges for SMGs that has ever been widely used in them, especially for military use. It is low velocity, which seriously limits effective range, and also has large diameter, which means that it penetrates pretty poorly. The .45 ACPs idea is to have a relatively easily controllable large diameter cartridge for pistols, since large diameter bullet is supposed to increase "stopping power".

[His Divine Shadow]

From what I've been told, 5.56 in a short barrel still outperforms calibers like 10mm and the like at the short ranges such a gun would be used at. Though it is ofcourse far from the optimal range for 5.56.

[[R_H]]

From what I've been told, 5.56 in a short barrel still outperforms calibers like 10mm and the like at the short ranges such a gun would be used at. Though it is ofcourse far from the optimal range for 5.56.

Outpreforms in what regards? For what I've read, it will be much more useful at long (ie >100m) ranges than a pistol caliber SMG, and at penetrating body armour, but what about against penetrating barriers (which 5.56 isn't too great at in general) and soft tissue damage?

[His Divine Shadow]

I was thinking of the Armor piercing issue. And from what I also figured was that ranges beyond 100m where irrelevant to these small sized guns since they would be dedicated close combat weapons.

[[R_H]]

7.62x25 mm Tokarev has potentially better penetration, but suffers at least mentally from its small diameter for a pistol round, and of course there has been very little active development of new weapons for it after the 1940s.

On the other hand, the Tokarev SMG loads can penetrate soft body armour, like the piddlely PDW calibers, while still being somewhat effective against soft tissue, unlike those damn piddlely PDW calibers.

[Coyote]

It's sad, as I pointed out in the MESS, that "Duke Nukem Forever" will be released before the Army gets its feces conglomerated on a replacement for the M-16 series.

[Mr. Coffee]

From what I've been told, 5.56 in a short barrel still outperforms calibers like 10mm and the like at the short ranges such a gun would be used at. Though it is ofcourse far from the optimal range for 5.56.

Outpreforms in what regards? For what I've read, it will be much more useful at long (ie >100m) ranges than a pistol caliber SMG, and at penetrating body armour, but what about against penetrating barriers (which 5.56 isn't too great at in general) and soft tissue damage?

Couple of vids showing 5.56 M855 performance versus 1/4 inch mild steel and 3/8 inch 500 Burnell steel. He's firing from a 24" barrel, but it gives you a general idea of the penetration 5.56 is capable of. Against mild steel, goes right on through at 80 and 205 yards, against hardened steel it makes a makes a nice divot but. Shorter barrels you won't be able to get close to the velocity you'll get with a full length, but for close range, 5.56 can still penetrate a lot of materials very easily.

1/4 inch mild steel @ 205 yards

3/8 inch 500 Burnell steel @ 80 yards

[Stark]

How does the mass and energy of a round vary with barrel length? What I mean is, 556 is a very light and fast round, and reducing the velocity obviously sucks, and heavier rounds are going to be less fussy - but do all rounds benefit from similar lengths? Are any rifle rounds going to be any good in a 12" barrel or do you need fat and slow (ie pistol) rounds?

[Mr. Coffee]

How does the mass and energy of a round vary with barrel length? What I mean is, 556 is a very light and fast round, and reducing the velocity obviously sucks, and heavier rounds are going to be less fussy - but do all rounds benefit from similar lengths? Are any rifle rounds going to be any good in a 12" barrel or do you need fat and slow (ie pistol) rounds?

Longer barrels allow for longer burn of the power which makes for higher pressures behind the bullet before it exits the barrel, hence higher velocity. At least that's how it was explained to me when I was a wee lad learning which end of the weapon points downrange.

[adam_grif]

Longer barrels allow for longer burn of the power which makes for higher pressures behind the bullet before it exits the barrel, hence higher velocity. At least that's how it was explained to me when I was a wee lad learning which end of the weapon points downrange.

That's correct. When you fire rounds not designed for a short barrel out of a short barrel, you get a lot of unburnt powder coming out the end, and a lower muzzle velocity on the round. If you trust Wikipedia, you can see this by going to the M16 page and then the M4 page, with 948 m/s for the former and 884 m/s with the latter.

The opposite does happen too, if it's some kind of fast burn powder and it's fired out of an unusually long barrel, all the powder burns, but then it's still going down the barrel so friction starts to slow it down.

Are any rifle rounds going to be any good in a 12" barrel or do you need fat and slow (ie pistol) rounds?

If a round is designed for a 12" barrel, then it will be optimal in a 12" barrel. The issue with short barrels on the M4 is that the standard 5.56 in military usage wasn't designed for a short barrel. IIRC there are some variants on 5.56 that are designed to work better with the M4, and have better performance because of this.

[Marcus Aurelius]

7.62x25 mm Tokarev has potentially better penetration, but suffers at least mentally from its small diameter for a pistol round, and of course there has been very little active development of new weapons for it after the 1940s.

On the other hand, the Tokarev SMG loads can penetrate soft body armour, like the piddlely PDW calibers, while still being somewhat effective against soft tissue, unlike those damn piddlely PDW calibers.

I have always thought that the soft tissue damage issue is largely a red herring, especially when it comes to SMGs, which would typically be used in full auto (well, except police use). The only sure way to rapidly disable a person with a pistol bullet is a central nervous system or vital organ hit, and the probability to get one increases with every hit. So, for an SMG controllability in burst fire and sufficient magazine capacity are much more important than individual bullet diameter. In that regard the PDWs do rather well.

Nevertheless, I do agree that the Tokarev is a good cartridge for SMGs. The high muzzle velocity also gives it a very good effective range for an SMG (easily 200 meters with a 250 mm barrel), although that is much less an issue now that it was in WW2, because SMGs are rarely used as general infantry weapons any more.

[[R_H]]

I find it interesting that when this topic (replacing direct impingement with a piston), both on SDN and on other sites/forums, very often HK's 416 is mentioned, but the Barrett REC7 (as it has a mid-length short stroke piston) rarely comes up.

The only sure way to rapidly disable a person with a pistol bullet is a central nervous system or vital organ hit, and the probability to get one increases with every hit. So, for an SMG controllability in burst fire and sufficient magazine capacity are much more important than individual bullet diameter. In that regard the PDWs do rather well.

I'd extend that and say the only sure way to rapidly disable a person with small arms is a central nervous system or vital organ hit. However, yawing, jacket fragmentation or expansion and an adequately large wound cavity do help in that regard.