PDW Cartridges

I hate to resurrect a long dead thread but I'm curious about something. If the design constraints are situated around the use of an AR mag, why not just neck up a 5.56x4mm case to 6x45mm and call it a day? Simple, easy, and effective.

You could use commonly available 75gr.-80gr. bullets and stay within the AR's mag constraints. You'll gain close to 100 fps over .223 Rem on the high end of the velocity range. Would you not notice less drop off in velocity in a shorter barrel configuration with the 6mm over the .224 cal.? It would be intereting to at least try. With the right combination of propellent and primer, it might be a viable option.

I do like the 6x35mm and 6x38mm SPEC rounds mentioned already. Interesting topic, to be sure.

I'm a .300 Blackout fanboy myself. I've got one 16" Rem 700 bolt gun already built and another 11" Howa being built. When NEA comes out with their PDW in that cartridge, I'll consider buying an upper to be used on my Bushmaster carbine.
 
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2bad4u2 said:
I hate to resurrect a long dead thread but I'm curious about something. If the design constraints are situated around the use of an AR mag, why not just neck up a 5.56x4mm case to 6x45mm and call it a day? Simple, easy, and effective.
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First thing I thought of after reading the above posts as well.
And also that it looks like a smaller 7.26x39mm
 
2bad4u2 said:
I hate to resurrect a long dead thread but I'm curious about something. If the design constraints are situated around the use of an AR mag, why not just neck up a 5.56x4mm case to 6x45mm and call it a day? Simple, easy, and effective.
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I;ve often wondered why the 7mm TCU never got brought into play for this. We used to shoot it out to 300m with a 10" barrel.

Uses 223 brass necked up and should feed from an AR marg.
 
50calshooter said:
Why do major manufacturers produce them then?
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I would think that's kinda obvious. The .223 Rem is the standard cartridge for the platform. It might not be the most optimal cartridge with a short barrel but it works.

Having to buy or load for a new cartridge would be a PITA for anyone looking to just add a carbine to their existing rifle. I wouldn't have bought my 11.5" at the time if I'd been forced to spend hundreds more to get set up for a new round.
 
The issue with 5.56 as pdw cartridge is the current ammunition IE: 62 grn SS109 is marginal at best in a short barrel configeration .The 77 grn is a far better round and delivers better terminal ballistics than the 62 grn projectile. Look at it this way manufactures come out with new cartridges every couple of years ! Why? to sell more guns it applies to the Military as well .Has the Military put out a request for ammunition for PDW's?? that should tell you something right there !
 
trekstor said:
Yes it does.
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no in fact it does not..... your avearge target shooter could give a #### how much energyy the 5.56 loses out of a short barrel, they just want a cool/fun gun that'll bang loud and throw fireballs. If it mattered to most , most wouldnt have super short 5.56 guns obviously.
 
winnipegger said:
no in fact it does not..... your avearge target shooter could give a f**k how much energyy the 5.56 loses out of a short barrel, they just want a cool/fun gun that'll bang loud and throw fireballs. If it mattered to most , most wouldnt have super short 5.56 guns obviously.
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+1. People who buy these PDW's are going to take one in a cartridge they can cheaply shoot with. In a lot of cases buyers already own a rifle or carbine and want to wn a PDW as well. Keeping the ammunition logistics as simple as possible nakes the most sense for a lot of people.
 
2bad4u2 said:
+1. People who buy these PDW's are going to take one in a cartridge they can cheaply shoot with. In a lot of cases buyers already own a rifle or carbine and want to wn a PDW as well. Keeping the ammunition logistics as simple as possible nakes the most sense for a lot of people.
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Yeah that makes sense, but some guys are making it sound as though 5.56 in a PDW format is about as lethal as throwing rocks. :confused: In a military application against armored vehicles, sure I get it. But in a personal defense or self defense situation how would 5.56 not get the job done? Even in a LE CQB role, I just don't see how 5.56 will make the target less dead. Of course this is just my ignorant opinion on the subject,
 
Russians got it right with the 9x39mm. Puts decent sized whole into people at the ranges a PDW would be appropriate and can be silenced very efficiently. If I had to have a PDW, I'd grab a 9A-91 with silencer.
 
I hate to resurrect a long dead thread but I'm curious about something. If the design constraints are situated around the use of an AR mag, why not just neck up a 5.56x4mm case to 6x45mm and call it a day? Simple, easy, and effective.
Click to expand...

AR mags are sized to fit 556 with 55-62gr bullets. The 77gr bullets work but they are starting to get a bit long for the case / mag combination.

Once you go to a longer and bigger bullet like the 87gr 6mm it helps to have a shortened case so that everything fits into the mag properly. Otherwise you end up seating the bullet too deep into the case neck.

The other thing with PDW rounds is that less powder capacity is helpful when using shorter barrels. This reduces noise when using suppressors and reduces flash.

Depending on the powder, the 6x38 SPEX pushes a bigger, longer bullet using roughly 1/3 less powder than the 556. The 300 Whisper can push huge subsonics with as little as 10gr of powder. This results in much less noise and virtually no flash at all. In comparison a 556 running a 7" barrel is a flame throwing monster.


I do like the 6x35mm and 6x38mm SPEX rounds mentioned already. Interesting topic, to be sure.

I'm a .300 Blackout fanboy myself. I've got one 16" Rem 700 bolt gun already built and another 11" Howa being built. When NEA comes out with their PDW in that cartridge, I'll consider buying an upper to be used on my Bushmaster carbine.
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I am a big fan of the 300 Whisper but its lack of velocity could be an issue at the extreme end of its range. A lighter, fast bullet combination may offer some improvements here.
 
Verdical Driver said:
I may be wrong, but aren't low velocity rounds undesirable for longer ranges compared to higher higher velocity rounds?

Isn't the idea of a PDW to be a small carbine to replace the pistol with something that can shoot farther than a pistol?
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Can you shoot further with a .45 carbine then a .45 pistol accurately?

I know I can. It's not a perfect solution, but it is a start.
 
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