dd357, I think your intentions, logic and presentation are great. The designation 6.2 makes sense to me-- 6.2 X .03937 = .244, I mean that’s about what the bullets mike, right? Your line of reasoning for naming it that seems flawless to me.
Best o’ luck, I’ll be watching.
NC, my initial designations were 6.17x42mm & .243 Kurtz, 6.2mm OCC was my final designation and I think the best.
Not really sure why you are chasing velocity here. So far, experience has shown that you can achieve greater terminal ballistics performance with heavier slower bullets. For example, 77/75 gr bullets outperform 62 and 55gr bullets at all ranges in the .223/5.56 cartridge. Same with the 6.8 SPC, the 115 and 110gr bullets tend to outperform the lighter 90 and 95gr bullets. Same with the 6.5G.
It seems better to go with a more efficient bullet. To what end are you chasing velocity for?
Strangely enough I came up with a similar concept back in 2008 which I posted on 65G.com, except I based it on the 5.45x39
http://www.65grendel.com/forum/showthread.php?p=41873#post41873
I was looking for High velocity for the CR, but you may be correct, as I have noted earlier David Tubb stated that the 90gr projectiles are the way to go. So it looks like the 90gr FMJ are going to be the way to go for a CR. 90gr Berger MTBT and 90gr Lapua Scenar for the MR.
I like it, 6x44mm, I like it. BUT what you propose is, dare I say impossible and stay within 2.260". What neck length would the 6x44mm have ?
The 5.45mm case diameter is smaller than the 6.2mm, less powder.
But I do like it, it just doesn’t add up.
You’re probably right. I didnt give it much thought but I wasnt sure what the dimensions should be to get the desired case capacity of ~30 grains.
Not just case capacity, but a 44mm case and 6mm VLDs, would have to go with a 41-42mm case.
I still like it, wander why the Ruskies didn’t go with it.
This is not exaclty related, but the December 09 edition of Precision Shooting had an article about the 6mmAR cartridge, with an “Ackley Improved” style shoulder.
I recognize that these cartridges don’t conform to what you were looking to accomplish but they are interesting just the same. Maybe think of them as the high-side benchmark of what can be done in 6mm out of an AR15 platform, if the only parameter is performance.
6mmAR is a 6.5 Grendel necked down. The case’s water capacity is 36 grains.
.223 case capacity is 29.5.
6mmAR “Turbo Improved” as the author calls it, water capacity with the 40 degree shoulder, giving more body volume, is 38 grains.
The author is Robert Whitley, I gather he is the father of the 6mmAR. He cites a website which I have not checked out yet-- 6mmAR.com. He mentions velocites of up to 2900 FPS with the 108 grain, 6mm bullets.
A pal of mine has been shooting 6mmAR for a year now. He’s a High Master in NRA High Power and the caliber has worked very well for him.
The only problem with the 6mmAR is the rate at which it’ll burn through barrels. All of the “stubby case” cartridges share that trait, so it’s not surprising. For competition shooters it works great, but as something to be shot in the volumes the military shoots? Eh…
On a related note, 6mm-SPC wildcats have been awfully successful, too.
-B
Looks promising. I like the simplicity of choosing either 90g FMJ or 90g Berger/Sierra HPBTs…heck, I bet the terminal performance of the match projs would probably be better at close range.
I have known about the 6mmAR and its variants for awhile, I think it’s a better round than the 6.5 Grendel. Mr. Whitley did a fine job, it’s a very accurate round.
A 15 year old won a High Power Championship with the 6mm AR. http://accurateshooter.wordpress.com/2010/02/24/young-champion-relies-on-tack-driving-6mmar-upper/ & http://accurateshooter.wordpress.com/2010/02/23/teen-tyler-rico-wins-nv-high-power-championship/
Some serious accuracy.
Only problem is it suffers from the same case diameter, magazine capacity and weight per round as the 6.5 Grendel for a military cartridge.
But still, I like it a lot, it’s a fine cartridge.
Should prove to be better at extended ranges, beyond 300m.
Anything new over these last few months?
Hornady has been sent a prototype.
But with the CT ammo now a reality the future of brass cased ammo in the military may go the way of the Dodo.
http://kitup.military.com/2010/07/army-closer-to-era-of-lightweight-ammo.html
http://kitup.military.com/2010/07/a-saw-at-half-the-weight-its-for-real.html
http://kitup.military.com/2010/07/lsat-test-shoot-video.html
Any update on this?
Last I heard from SSS was they ran figures, have the cartridge drawings and specs. They said the ballistics(figures) outperform the 5.56, 6x45(6mm/.223) & 6.8spc but not the 6.5 Grendel. Which I knew before that it wouldn’t outperform the Grendel and it wasn’t intended to, it beats the Gendel in cartridge capacity. I need to call and check up, its been awhile.