Originally Posted by Drang
That kind of knocks the whole thing in the head. If there was ever a Garand design made in anything but .30 and .276, I have not seen or heard of it. (Other than some one off attempts at sporterizing surplus.)The winning American rifle design was the M1 Garand, which was originally designed to use the .270 Winchester cartridge.
Code Name: JET STREAM
That is not the only factual error in the linked article.
Given that 6.5mm has bullets with among the highest BC, I don't understand why they don't simultaneously adopt a 6.5CM platform for DMR/long-range/machine gun work and then build a proper new 6.5 based on a 5.56 case (the 6.5PCC is close). I'd actually take a .300BLK and neck it to 6.5 with as steep a shoulder as possible and design a bullet with a decent cannelure, so the bullet doesn't need to sit deep in the neck (think a 6.5 Grendel, but in a 5.56 case, instead of a .220 Russian case).
It would take some work and engineering, but I can almost guarantee you could build a better round, in theory if you designed the bullet right, you could use the same bullet (not ammo, but same bullet) and reduce manufacturing costs. In the process, a standardized bullet weight would be established (I'm guessing right at 100-grains if not 120), barrel twists would be standardized. With 5.56 as the parent case, it will only require new barrels, new recoil springs (maybe), and maybe minor gas adjustments to the M4/M16 family. Bolts can stay the same, mags the same, etc.
In addition 6.5CM can be chambered in just about anything that is currently in 7.62NATO, with a barrel swap and minor tuning.
Why do we need to replace good guns if we can rebuild them and chamber them in a better round? But then again, I'm not in military procurement, so being logical doesn't matter much.
It was enough that I didn't bother reading the whole article to look for more nonsense. l
Code Name: JET STREAM
My money is still on “Happen; not going to.”
If we have to march off into the next world, let us walk there on the bodies of our enemies.
I'm not up to date on the big issue of what's wrong with the current round. If it has to do with poor performance because of bullet velocity, would not increasing the M4's barrel length by two inches and also tweaking the bullet's design remedy most complaints? When I was a kid, I would read articles telling of the 7.62 Nato's shortcomings and extolling virtues of the all new .22 cal round that "ought to be adopted". Then it was.
@DocGKR has reported several times that 6.5CM (and any other case with a steeper shoulder) doesn't feed in self-loaders as reliably as .260 Remington. There are people he couldn't talk about in detail putting a lot of .260 through self-loaders.
For a machine gun, it may be relevant that smaller bores with the same case volume tend to erode throats faster.
Doing a .300BK-like solution gives up too much case volume to be a solution to the long-range problem that is ostensibly motivating this activity.
I still can't figure out why 6.8 SPC isn't the answer to this question, unless they want to spend China's bond-purchase money on all-new rifles fer e'er'body to get a case with 35 grains of powder. The latter may be it. The 7.62x51 has ~80 percent more powder than a 5.56x45. Rather than that, maybe what is wanted is 40-50 percent more. Off the top of my head, I can't think of any remotely popular cartridge in that space.
I'm not a firearms designer, but if I was working on a program for this, and it was agreed that nobody is interested in just another wildcat that you can run in an AR, my first draft outline would be a lengthened SPC case with ~35-38 grains powder capacity (or whatever was needed to meet ballistic targets, doing cartridge development work with a series of cheap test barrels in addition to pressure test barrels - maybe build a small fleet of Remages with single-shot receivers) and stretch the magwell section (upper, lower and bolt carrier) of an AR to fit it. Adjust the recoil system and keep everything else the same, except maybe go to a piston system with provision for an easily-cleaned suppressor for the piston chamber exhaust. Might come out quieter with a can than a suppressed DI gun.
If the resources were available, or if it turned out there wasn't a very specific 6.8 projectile already engineered that we were expected to use, I might do some development of a 6.5mm version just to have that in my pocket in case someone who mattered asked.
Nearing the end... "Can we do this in 6.5mm?"
"Yeah, how about tomorrow? And here's our data so far."
Last edited by OlongJohnson; 11-12-2018 at 12:32 PM.
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Not another dime.
The AMU developed .264 USA and .270 USA would be viable options; for that matter an updated version of the British .270 or .280 cartridges for the post-WWII EM2 would probably also be viable. The other option is to use a cased telescoping design.
The main problem is that the cartridge and projectiles must be selected FIRST, then tell vendors to design weapons that function with the optimized cartridge that was selected. Having vendors submit different cartridges with their weapons is illogical, as you end up with the same type of fiasco as occurred with XM17....
Facts matter...Feelings Can Lie
I agree that requiring the DOD to shyte or get off the pot and do some good old fashioned engineering to come up with the cartridge that features the ballistics they want might be a good thing. Like have the folks at Picatinny or wherever competence lies take it on. Which perhaps may already have happened.
I'm curious about details of the "AR-12" that was developed along with the "USA" cartridges. Info is thin on the ground. Anyone have links?
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Not another dime.
This ^^^.
Plus in the big picture machine guns (belt fed) do the majority of the killing with small arms. What ever round is selected need to be a good machinegun cartridge first, rifle cartridge second.
The round will in some ways dictate the design of your new rifle. For example, are you going to have a tapered case or a straight wall case ? That will dictate the shape of your magazines for optimal feeding. Tapered cases need constant curve magazines for optimal feeding. The choice of round and magazine in turn drives the design of your rifle.
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