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Page AR-15 » AR Variants
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Posted: 10/16/2008 10:20:56 AM EDT
I was wondering if there was a cartridge that was just a 5.56 with the shoulder taken out to make a straight wall case.  It would seem to me it would end up at about a 9mm and would make a nice all purpose round and would only require a barrel change.

I found the .357 Mag Rimless listed on the following thread:

Is this round essentially what I'm talking about?  If so, where are barrels and ammo available?  

Link Posted: 10/16/2008 10:44:33 AM EDT
I think the closest is the M1 Carbine round. Notice how the are both approximately the same length and the original .223 projectiles were 55gr and the carbine is 110. Hmmm,
Link Posted: 10/16/2008 10:50:36 AM EDT
9mm Super Cooper?
Link Posted: 10/16/2008 10:55:40 AM EDT
I'm not familiar with the 9mm super cooper.  Is that what I am talking about?  I want it to be the exact case just straighwall instead of necked down.  The idea is to minimize any need for different parts (bolt, mag, etc).  I don't think the .30 Carbine fits that bill.  
Link Posted: 10/16/2008 1:22:41 PM EDT
Sounds like the 338 whisper,  221 fireball necked up to 338.  JD Jones developed it.
This is from the ssk industries web site regarding the whispers:

"Whispers®: A wide range of calibers encompass the 'Whisper®' series of cartridges. A "Whisper®" cartridge must be capable of sub-sonic extreme accuracy with very heavy bullets for its caliber; i.e. 240 grains in 30, as well as moderate to high velocity while maintaining excellent accuracy with light bullets for the caliber; i.e. 125 at 2300 FPS in 30. The 300 Whisper® was the first of the series, and, contrary to what you may have read about it, the fact of the matter is the cartridge was designed as a multi-purpose cartridge from the beginning. Its design parameters, in addition to the ballistics quoted above, were that it must be capable of being used in the AR-15/M-16 family of rifles, Contenders and bolt action rifles as well as being easily suppressed. I know that because I invented it. It revolutionized the tactical suppressed sub-sonic field in controllability in full auto, power and accuracy. It has been very successful and has gained wide acceptance as a hunting round for mid-size game, such as deer, and has probably taken a wider variety of game than any other handgun cartridge in the same time span. Due to its small case capacity, its recoil is very mild. One Whisper® series from 6 mm, 6.5 mm, 7mm, 300 and 338 is based on the 221 fireball case. Another series is based on the 7 BR case in 338, 375 and 416 caliber to convert 308 case head size actions. Another used the 460 Weatherby case for 50 caliber conversions to 300 Win Mag case head size rifles. Others use rimmed cases, such as the 50-70-750, for use in single shots."

Link Posted: 10/16/2008 7:59:07 PM EDT
does the .338 Whisper use  the standard bolt face and magazine of the 5.56 AR?
Link Posted: 10/17/2008 6:06:05 AM EDT

does the .338 Whisper use  the standard bolt face and magazine of the 5.56 AR?

I would think so, the 221 fireball is just a shortened version of the 223, same diameter case and same case head.  The larger and longer 338 bullet would bring the overall cartridge lenth closer to the 223.  SSK Industries has pictures of the cartridge on their web site.  Click on the "cartridge" button and scroll down.  Sorry, but I don't know how to post a direct link.
Link Posted: 10/17/2008 6:12:45 AM EDT

does the .338 Whisper use  the standard bolt face and magazine of the 5.56 AR?

I think so.
Link Posted: 10/17/2008 6:15:10 AM EDT
Here ya go...

SSK Cartridges

Link Posted: 10/17/2008 6:24:02 AM EDT
Link Posted: 10/17/2008 5:19:06 PM EDT
Don't think it would work.  I tried turning off the rims on 357 maximum brass and chambering a barrel, but the forward rib on the mag cants the round offline.   You might get an upper chambered for the 9mm mag case.  I think its like a rimless 357 mag.
Link Posted: 10/18/2008 10:16:27 AM EDT
According to SSK the .338 Whisper uses the AR10 bolt and the .300 Whisper uses the AR15 bolt, so no luck there.  From their email:  "Sir, the 300 uses the Ar-15 , the 338 uses the AR-10. They both use standard bolts and mags."

The 338/223 looks like the closest to what I'm looking for but is not really available.

Thanks to all for the info, looks like I will have to find another option.  The .300 Whisper looks interesting...
Link Posted: 10/18/2008 10:21:56 AM EDT
.338 Spectre uses 6.8 bolt and mags.
Link Posted: 10/18/2008 10:22:22 AM EDT
Look, the case head on 5.56 is only .378, so you can't support a full length 9MM.  I wouldn't go longer than 9x23.
Link Posted: 10/18/2008 9:03:37 PM EDT

338 Whisper exists in two versions.  Version 1 uses 221 Fireball brass, fits standard AR mag, bolt, etc.  Not a very popular version and indeed very similar to the 338/223 Straight from Atchinson.  Version 2 uses 7 BR brass and is offered in bolt guns and the larger platforms (AR10, LR308).

223 brass cut short can be made to accept a .357 bullet, this is how Randall made a 357 Max Rimless.  Feeding issues will occur with straight cases of greater than 1.25" length, unless you make the chamber sloppy.  Randall cut the cases shorter and made 357 Mag Rimless.  No real interest from the community so it was left as an experiment.

30 Rem brass cut to 1.575 will take 9mm bullets, we have dies for this, called it 9mm CQB, a counterpart to the 9 x 39 Grom which is unavailable in the US (but you can make 35 PPC which is very similar to the Grom).  Back then, 30 Rem brass was scarce like hen's teeth so we dropped the project.

But feeding from the mag of the long straight case is the issue, you need case taper to help address this and thus you need a larger case.  As a result, 35 PPC ends up the best solution.
Link Posted: 10/19/2008 8:29:22 AM EDT
Thanks Marty for the info.  You always come through.
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