5.56 versus 7.62 (or some 6mm variant) in a modern general purpose carbine (2024)

KSGM

A thought inspired by the recent AR vs M14 topic, but created anew to keep things clean.

With the advent of light(er) weight large frame, and even small(ish) frame, .30 caliber AR10-type rifles, would you be eager to swap your "general purpose" 5.56mm carbine?

This is assuming the ammunition cost is not a factor.

Now that these larger-caliber-capable rifles are lighter and smaller, are the performance advantages worth the (now less) extra weight and bulk and reduced ammo capacity?

Keep in mind that this question is posed in the context of an across-the-board modern infantry GI rifle. That being said, all the contemporary add-ons are in play: variable optics, MFALs, flashlights, silencers, etc.

This is a rifle to replace your current favorite "go-to" 11.5"-18" AR15 in 5.56; a 7.62x51 or 6.5CM with a 14"-18" barrel.

I am sure I didn't close all the loopholes, in this OP. We'll address them as they arise.

OttoSig

No, Ammo is lighter, capacity is higher, and in my use cases there is about .5% chance I am shooting through armor.

Also about a 98% chance the engagement is within 50-75 yards.

So why would I go with bigger and heavier.

None of us are Army/Marine Generals where this conversation is even warranted. It can be a fun one sure, but no, my 5.56 ARs are more than enough for what I need.

If I'm out hunting pigs or something like that then sure, we can talk about other calibers, but I don't think that's what you're asking.

old rugged cross

My take is absolutely. An upgrade in firepower is always a big plus, imho.
That being said. Out side of the Scar17 I do not think is is possible to any great degree with the AR10.
While I like the 10. It is what it is.

"Practice like you want to play in the game"

Voshterkoff

For military, new high pressure .308 sized rounds could be a game changer, but we will have to see how that plays out. The other benefit would be better penetration on light cover like trees and some structures. Of course the limited ammo carrying capacity will limit this benefit.

Separate from that, I’ll TLDR my search for a “go to rifle” replacement. My primary relocation site in free America is in grizzly territory. As a go-to rifle should be able to take care of most situations, I have studied 30 caliber options. After watching competition footage of people shooting 300 meter targets with 7.62x39, I don’t think there a good reason against a modern lightweight 7.62x51. Since I can’t buy or build anything, I have been looking at parts to assemble an AR10 in the future. ROAM offers a magnesium alloy receiver set and rail that in their lightweight oriented build weighs 6 pounds. I wouldn’t call it a “go to war” rifle, but should cover my needs as a Second Amendment enthusiast. I’m also not going to sell any of my 5.56 or 7.62x39 rifles.

The other instance I could see is living in wide open farmland or open range. Something like a lightweight 6.5 would make sense. This could apply in a military situation, but that’s offset by urban setting, so I don’t know.

KSGM

quote:

Out side of the Scar17 I do not think is is possible to any great degree with the AR10.
While I like the 10. It is what it is.

Why do you say that? I think both KAC and LMT have made some pretty compelling 6.5CM "carbines".

One sticky spot for me is the application of a silencer. The .30 cal carbine is already bigger and heavier, and a silencer to tame these larger cartridges has to be significantly larger and heavier than the 5.56 cans.

7.62x51 offerings from KAC and LMT come in at 8.5 pounds. 16" barrel on the KAC; 13" or 16" on the LMT. Wilson has a 16" 6.5 gun that also weighs 8.5 pounds.

CD228

KSGM

quote:

I tried a shorter 7.62

What did you try, and what were more of your specific impressions of the concept?

Again, this query isn't limited to the confines of what might be our actual probable use case as civilians in 2024 America.

Is the concept a good idea in general? Are the advantages offered by 7.62 or 6.5 on the modern battlefield worth the compromises in weapon and ammo weight and load limitations, even if they're relatively minimal?

This is assuming ammo cost and rifle cost are non-factors.

Is 5.56mm better as a general-issue fighting rifle caliber?

OttoSig

quote:

Originally posted by KSGM:

quote:

I tried a shorter 7.62

What did you try, and what were more of your specific impressions of the concept?

Again, this query isn't limited to the confines of what might be our actual probable use case as civilians in 2024 America.

Is the concept a good idea in general? Are the advantages offered by 7.62 or 6.5 on the modern battlefield worth the compromises in weapon and ammo weight and load limitations, even if they're relatively minimal?

This is assuming ammo cost and rifle cost are non-factors.

Is 5.56mm better as a general-issue fighting rifle caliber?

If it's a war with Russia or China (and a plethora of other nations) then yes, unequivocally a larger round is better when facing body armor. That's not a situation where opinion matters, that a fact-based answer based off modern body armor our likeliest adversaries use.

That's a one post thread.

Is there some other context you would like to discuss the comparison in?

KSGM

Well, not really.

Explains why the NGSW steered the way it did, and why weapons like the aforementioned LMT, KAC, and Wilson rifles are gaining more traction.

So the weight/bulk of weapon and ammo, and the limitation in on-board and carried ammo capacity, of 7.62x51 or similar cartridges is worth it, to gain the ballistic performance against a peer or "near-peer" opponent on the modern battlefield.

OttoSig

quote:

Originally posted by KSGM:
Well, not really.

Explains why the NGSW steered the way it did, and why weapons like the aforementioned LMT, KAC, and Wilson rifles are gaining more traction.

So the weight/bulk of weapon and ammo, and the limitation in on-board and carried ammo capacity, of 7.62x51 or similar cartridges is worth it, to gain the ballistic performance against a peer or "near-peer" opponent on the modern battlefield.

Yes, and the attempt to be able to consolidate the required platforms infantry use.

WWII - Garand and BAR
Vietnam - M16 and M60
Recent - M4A1 and M249

The desire is to eliminate different platforms and instead offer Mod-X for light machine gun, battle rifle, etc. Whether that is actually a positive result is still to be seen.

Whether the WHOLE idea is the right one depends on if we go to war or not, if we don't, then we wasted tons of money. If we do, then we'll be GD glad we aren't shooting at armored infantry with an M4.

old rugged cross

Short answer is yes.

What is a modern battlefield?
That could be anything.

In a real combat situation do you want 120rds of 7.62 and a 12lb rifle or 150 rds of 5.56 and 10.5lb rifle.

To answer that you would need the input from those that have been there and done that.

And there are no absolutes. Certainly some situations warrant one over the other.

And no I do not want a 6.5. Maybe the 6.8. Presonal preference is the reason.

"Practice like you want to play in the game"

KSGM

A modern battlefield is defined, by me for the purpose of this thread, as a fight in which the belligerents are peers (or nearly peers) in terms of equipment and technology.

We all know different guns and calibers have their different ideal applications.

I am curious if people think that, on that modern battlefield, all our troops who are currently issued an M4 in 5.56 would be better-off with an AR10 (or similar rifle) in 7.62x51 (or similar caliber).

RichardC

quote:

Originally posted by car541:
We occasionally have ammo manufacturers come in and do ballistic performance demonstrations (shooting gold dots and HST's though glass, denim, drywall, etc into ballistic jello). At one of them, after having the engineer drone on for a while about barrier performance in various pistol calibers and 5.56, I asked what the FBI performance standard was for 12 guage and .308. The answer was illuminating: "there isn't one, they couldn't find a case where a COM hit from a 12 guage or 308 didnt cease hostilities instantly, so all of this testing was deemed unnecessary" (perhaps not the exact words, but close enough).

https://sigforum.com/eve/forum...935/m/1350000905/p/2

old rugged cross

Again, short answer is yes.

Do I think the M4 is a horrible rifle in a horrible caliber for a fighting tool. No I don't. Just answering your question from my perspective.

"Practice like you want to play in the game"

JoshNC

The 5.56 M4 does most things very very well. With that said, I think a 14.5 to 16” 6.5cm with CHF CL medium contour barrel makes a lot of sense. It suffers from less ammunition carrying capacity compared to 5.56. 6.5cm gives more standoff distance, more terminal performance at longer ranges, all with light recoil. A good CHF CL barrel will give longer service life than SS.

---------------------------------------------
"AND YEA THOUGH THE HINDUS SPEAK OF KARMA, I IMPLORE YOU...GIVE HER A BREAK, LORD". - Clark W. Griswald

CD228

quote:

Originally posted by KSGM:

quote:

I tried a shorter 7.62

What did you try, and what were more of your specific impressions of the concept?

Again, this query isn't limited to the confines of what might be our actual probable use case as civilians in 2024 America.

Is the concept a good idea in general? Are the advantages offered by 7.62 or 6.5 on the modern battlefield worth the compromises in weapon and ammo weight and load limitations, even if they're relatively minimal?

This is assuming ammo cost and rifle cost are non-factors.

Is 5.56mm better as a general-issue fighting rifle caliber?

I went with a 16-18 inch AR-10 for comparison.

Based on what I saw in Iraq and ASTAN and I've been seeing at NTC, JRTC,JMRC and my duty position, I'll take the lighter weight M4A1 Carbine with it higher hit probability and the better ability to hit specific body locations. For now, if certain conditions are met i would gladly jump caliber.

7.62mm performance vs armor is known. There is a reason that the Interm Combat Service Rifle in 7.62mm popped up and then disappeared. There are some proposed armor piercing rounds being worked that are going to be very interesting, check out Aeroshell AP amongst others. M80A1 and M855A1 performance against armor can be found, but I don't believe that the Army officially released their performance. Also, it seems every time we come up with a new round, some one come up with an armor that stops it. I believe i'll be trying to deal with armored opponents by shooting above/below their armor, with a crew served or with explosives.

The 7.62mm does perform better at longer ranges, but the actuall engagment ranges I expect in LSCO will be determined by LOS. In some environments the longer legs of the 7.62mm might be usefull. But, if you are in City/town or woods the longer range capability will not be as useful.

Terminal performance is heavily influenced by shot placement and I can place my shots better with 5.56mm.

I am interested to see how the XM-7 performs. There is some info I want to see before I pass judgement. I think the new Squad Automatic weapon is the right answer, but I'm an MK48 fan.

This message has been edited. Last edited by: CD228,

KSGM

I shared these topics with a friend. He's in no more of a position of authority on the matter than I.

He thought it might be good to have one 7.62 guy per team or squad. He thought the overall round count sacrifice was too extreme, in going full-7.62.

Maybe not a terrible idea. The .308 is in use anyway, in both DMRs and Machine guns. It adds a small new layer of intricacy at the squad level, if the squad doesn't already employ a designated marksman, but it's not too bad.

The .308 guy(s) can engage in the same tactics as the rest of the squad (while being mindful of a reduced rate of fire, to conserve their limited ammo), and they'd be able to offer their extra performance in specific circ*mstances where it's most useful.

PGT

I have a POF Rogue which in 7.62 NATO in an AR15 package and weighs 6lbs. Other than lower capacity mags for the form factor, this is just as handy as typical AR15 carbine.

Interestingly, my original AR10 Guatemalan is nearly as handy and doesn't weigh much more.

Now, if we want to talk 13" barreled carbines with folding stocks....that's where things get interesting but piston guns shine for reliability but are not as quick to point and handle differently than a DI short'ish carbine

OttoSig

quote:

Originally posted by KSGM:
I shared these topics with a friend. He's in no more of a position of authority on the matter than I.

He thought it might be good to have one 7.62 guy per team or squad. He thought the overall round count sacrifice was too extreme, in going full-7.62.

Maybe not a terrible idea. The .308 is in use anyway, in both DMRs and Machine guns. It adds a small new layer of intricacy at the squad level, if the squad doesn't already employ a designated marksman, but it's not too bad.

The .308 guy(s) can engage in the same tactics as the rest of the squad (while being mindful of a reduced rate of fire, to conserve their limited ammo), and they'd be able to offer their extra performance in specific circ*mstances where it's most useful.

This is how its done now and previously, on paper anyway. And why the Army is going with the Sig rifle to have 1 round, 1 platform, multiple roles.

The mention of longevity on barrels and what not is not a concern in combat applications. Nobody uses a barrel or part to expiration.

Lifespan is measured in days/weeks/maybe months. Items are damaged, lost, generally f*cked up and require replacement WAY before they wear out. So that tends to be a moot point. You could use 7WSM and not have many wear out.

KSGM

quote:

This is how its done now and previously, on paper anyway.

If a .308 is integrated at the team or squad level now, isn't it in the form of a DMR; not necessarily a "battle rifle"?

A DMR configuration will lack the broader applicability of a shorter, lighter, potentially suppressed, lower magnification setup.