If the US armed forces were to replace the 5...

If the US armed forces were to replace the 5.56 with something modern completely ignoring economic implications what would be the best intermediate cartridge available?

Picture related is an example of a modern intermediate cartridge.

Attached: 300 aac.jpg (800x800, 52K)

Blackout, Grendel, etc are all right out. Their number one design criteria has been to fit into the standard STANAG, and to fit with as little changes as possible to your base AR15. If you're going to start over form scratch again you sure as hell won't chain yourself to that.

.224 Valkyrie

Anything in the 650 range inbetween 556 and 762

Something with less mass and equivalent overall volume than 5.56, more efficient powder, and a more aero-dynamic projectile than 77gr TMK. Polymer telescoping or caseless would be nice too, since we wouldn't be competing with Southeast Asia for brass.

If you ignore economic implications, you can make a new base.

The answer is 6.5 Creedmoore

This.

This right here. Mag length is the real bottleneck. Small Frame AR10s are awesome and that would open the door for 7.62x45(goddamn soviets). 7mm UIAC, or proper 6.5grendel

People who think there are better options than 5.56 in 2018 don't know shit about guns.

battle rifles are outdated and dumb

If you're sticking with 5.56 caliber, 224 Valk is better.

5.56 NATO is 60's technology. We know a lot more about how to create a more efficient bottleneck in a case, and how to make higher BC bullets with better terminal ballistics.

7.62RFN

>battle rifles are outdated
As Cold War II: Electric Boogaloo ramps up, they're going to become more relevant again.

and why is that?

556 within 200m is like inserting a banana into someone’s chest. Pair that with light recoil and weight, and it’s the best intermediate cartridge out.

.264 USA

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It's a lot easier to get through ceramic armor (especially at range) when you have a larger, more powerful cartridge to work with. And before you say something stupid like, "5.56 is inherently more armor-piercing than .308!" remember that there are things such as discarding-sabot armor-piercing rounds that take advantage of a big bore to shoot thinner bullets at higher speeds than can be achieved out of a smaller-bore barrel of the same length with the same chamber pressure.

With reasonable funding pic related would be complete and already rolling off of the production lines in a month.

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>yfw it gets cancelled the day after the Army officially adopts it.
>yfw there's still going to be no new ammo designs that bring ammo into the 21st century.

Picture related has a velocity inferior to 600 m/s at 100 yards, which makes it an intermediate velocity cartridge at usual fighting ranges. That's not ideal for terminal ballistics. I would rather take 6.8 SPC, it hits harder at faster velocity.

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5.45, if engaging targets at distances greater than the effective range of 5.45, your average infentryman will not make a hit, ever. So, general issue-5.45, anything at longer ranges is 6.5

why 5.45? its literally a worse 5.56.

It has a better ballistic coefficient (being longer an thinner) and performs extremely well in differing barrel lengths, doen to 8". It tumbles reliably at speeds much slower than 5.56. Im not saying 5.56 is bad at all, but i think 5.45 is marginally better for an average infantryman.

You are fat and slow, not unlike a cow. Go on a diet.

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It also is only slightly lower in velocity than 5.56 (~100fps for actual military loadings) and can use the same grain bullets. The slightly slower velocity is more than made up for by the way it performs at a distance, comparably

basically this

I have handloaded .308 with saboted .224 bullets and while the muzzle velocity (over 1300 m/s) and penetration (punched through 10mm armor plate from an old APC with a freaking soft point bullet) were impressive the accuracy was not and I really doubt it would work well in a semiauto rifle.

Probably finish and improve the various caseless ammo projects abandoned near the end of the Cold War.

That's just a matter of the projectile, not the cartridge as a whole.

> tumbles reliably
We're done with that these days though.

Caseless ammo will never work. Case has two very important features which are really hard to solve with other means; protection of the propellant from the elements and forming a gas seal when the gun is fired.

You would know both of those problems have already been solved if you had spent 5 minutes googling it.

6.8 SPC has atrocious velocity even at the muzzle. It gets 2600 FPS maximum.

I would say the top three are 6mm saw, 280 british, and 224 valkyrie

>and performs extremely well in differing barrel lengths, doen to 8"
An AKs-74u with 7n6 really doesn't perform much better than a Mk.18 with M855A1, they're pretty comparable, in that they work for CQB ranges, but they're really bad at any longer distances, also both being loud and bright as shit, which isn't the best for house clearing, that shit will disorient you.

Developing better loads for each would basically put both of them on the same level anyway.

>That's just a matter of the projectile, not the cartridge as a whole.
Not really. The 5.56 cartridge is constrained by a relatively long case/short OAL. The 5.56 case is about 5mm longer (not 6mm, 5.45x39 is really closer to 40), but the OAL is within half a millimeter. This means 5.56 is stuck with short ogive bullets -- look how retarded-looking m855a1 is, it has at least as much bearing surface as ogive.

You simply can't put a decent long-range projectile in 5.56x45.

Attached: m855a1.jpg (660x440, 62K)

Since the US never signed the Hague Conventions, I'd say get expanding rounds. Guarantees that a drugged up Terry Talibunny gets ripped apart.

6.5 Swe or Creed.

I dreadfully hope for a replacement for 5.56
I'll take anything, even fucking 6.8, so long as there is wide spread military, police, and industry adoption, as well as simple barrel and bolt conversion kits for my AR.