graylion said:

I am uncertain about the carbine - who gets it? HE slingers and machine gunners? Snipers?

I think the guys who are concerned should figure that out by themself.
If they want a PDW give it to them. Same with carbine or pistol.

Personally I don't think machine gunners need a secondary weapon at all. They have a machine gun.

graylion said:

I have been playing with a cartridge that would kind of do the job on defeating Lvl IV armour out to 100m, But a pistol cartridge it ain't. A carbine catridge sister to the .277 Fury? Yes. This thing will not fit into a handgrip unless it is a single stack, so P90 style mags it is, even for the pistol :( Bullet Aluminium with steel core: http://www.geoffrey-kolbe.com/cgi-bin/drag_working.cgi?unit_length=mm.&weight_unit=grains&bullet_name=GLS+PDW+II&re_calculate=yes&boundary_layer=L%2FT&entry=return&diameter=7.51&length=21&nose=14&meplat=0&drive_band=7.8&base_diameter=5&angle=8.5&boat_tail=5&secant_radius=5.7&weight=49.2&density=5.2 And, assuming our PDW has a 200mm barrel, I get this (assuming same pressure as military load for .277 Fury).  Google Docs 7.5 Graylion Load R24.png Read more from Google Docs

Recoil energy is 8J, that's about equivalent to .40 S&W

autogun said:

If you want to maximise penetration above all else in a pistol/PDW, then see the 6.5mm CBJ.

With this one IMHO its more about the projectile.
But something like this based on or in the power range of the 7,5 BRNO might deliver the desired penetration.

I am also curious how a saboted penetrator like the one of the 6.5 CBJ but fired from a 5.7x28 or 4,6x30 would perform.

graylion said:

       stancrist said: 9mm has also proven quite effective in similar mass shootings, so if that's the basis for pistol caliber there is no reason to change.

Not my point. I was attacking the statement that "nobody wants a pistol in 5.7"

Sorry, I was imprecise.  I did not mean literally "nobody" wants a 5.7mm pistol.  I meant that no army wants to switch from 9mm pistols to 5.7mm pistols.

graylion said:

       stancrist said: The US Army apparently does not share your opinion, because the XM5 "rifle" with its 13-inch barrel is, at best, really just a carbine, if not actually in the SBR class.

And yet it is 3" longer (36") than an M4 - so I am calling BS.

How is it BS?  SBR = Short Barrel Rifle, not Short Overall Length Rifle.

The M4 carbine has a 14.5" barrel.  The XM5 rifle has a 13.0" barrel.

stancrist said:

How is it BS?  SBR = Short Barrel Rifle, not Short Overall Length Rifle. The M4 carbine has a 14.5" barrel.  The XM5 rifle has a 13.0" barrel.

Cos it is missing the point - carriability

schnuersi said:

Well the XM5 might be a carbine for .30 cal or full power rifles...

Well, the 6.8 is a full-power cartridge.

schnuersi said:

...but its size and weight is not in the same class as the common 5,56 carbines.

The XM5 is certainly heavier than the M4, but overall length is about the same (~30 inches with stock retracted).

schnuersi said:

Its so large and heavy that its completly unsuitable as PDW or secondary weapon.

I agree.  However, the Swedes apparently think an 8.4-lb rifle is suitable for use as a PDW or secondary weapon.  

schnuersi said:

5.7 has less recoil, flatter trajectory and larger capacity magazines. Which makes it the better choice.

Less recoil would help, but the flatter trajectory won't make a bit of difference for most soldiers.

And we're looking at 20-rd mags for the FN 5.7 pistol versus 17-rd mags for the 9mm M17 pistol.

The hard truth is that 5.7 is just not enough better to justify the change.

Especially seeing as how pistols are "almost useless" in military combat.  

schnuersi said:

I am also curious how a saboted penetrator like the one of the 6.5 CBJ but fired from a 5.7x28 or 4,6x30 would perform.

That seems somewhat less than feasible. 

6.5 CBJ penetrator is only 4mm diameter.

stancrist said:

The hard truth is that 5.7 is just not enough better to justify the change. Especially seeing as how pistols are "almost useless" in military combat.

Not by itself I agree. But if 5.7 would be introduced as a cartidge for mass issue of PDWs it would make a lot of sense to change the pistols over as well.

stancrist said:

Less recoil would help, but the flatter trajectory won't make a bit of difference for most soldiers.

I was thinking of PDW use. At 50 or 100 m the trajectory of 5.7 or 4.6 does make a difference. Compared to 9x19 there is a noticable difference in hit propability.

stancrist said:

That seems somewhat less than feasible. 6.5 CBJ penetrator is only 4mm diameter.

The current AP loadings for 4,6 and 5,7 do not use tungsten. They are all with steel core. Since both have ME in the same region as 6,5 CBJ there most likely will be an increase in penetration.

For 4.6 it propably won't make much sense to use a 4 mm slug with sabot. A 4 mm hard core with a lightweight bullet seems more feasible.

For the 5.7 it might allready be feasible to use a saboted 4 mm slug.