We've Missed the Boat By Not Making 6x45 The Primary AR15 Cartridge

[Llama Bob]

It's the velocity that makes all the difference. Run the numbers yourself.

Just did, and you're wrong just like I knew you would be. The 6x45 had more energy at 400, and the gap widens the further out you go.

 

[Llama Bob]

Woulda, coulda, shoulda.

BTW, Vietnam "body counts" were notoriously over inflated. I wouldn't use them as "proof" that US military marksmanship or tactics have devolved.

I'm not saying marksmanship has evolved or devolved or anything else. I'm saying if it takes you 100,000 OR 250,000 rounds to get a kill, it can't be called marksmanship. Get that number down to say 20 and we can talk.

 

[VoodooMountain]

Just did, and you're wrong just like I knew you would be. The 6x45 had more energy at 400, and the gap widens the further out you go.

I would love to see how you came up with that

 

[Llama Bob]

Simple - I put the respective velocities for 16" guns for M262Mod1 (2680 ft/s) and a reasonable low temp sensitivity 55KPSI 6x45 95gr SMK load (2490 ft/s) into JBM ballistics and left my atmospherics the way they were (1 mile elevation, 59F, standard pressure at elevation/temp).

For 5.56:
400y 1926.9 ft/s 634.7 ft-lbs
For 6x45:
400y 1887.5 ft/s 751.4 ft-lbs

As you can see, the 6x45 has almost 20% more energy. The gap gets wider if you move to lower elevation or longer distance.

Believe it or not, I didn't just randomly post this thread. The 6x45 does really outperform the 5.56 at pretty much every conceivable scenario.

 

[VoodooMountain]

That's how we came up with different results. My velocity for the 223 was at about 2800 fps which is what I get with my handloads and the 75bthp in my ar's.

I used 2450fps for the 6x45


At those numbers the energy was awash at 400 yards with velocity going to the 223. Trajectory was also flatter for the 223

 

[Llama Bob]

That's how we came up with different results. My velocity for the 223 was at about 2800 fps which is what I get with my handloads and the 75bthp in my ar's.

Then you're running a barrel longer than 16" or pressures higher than 55KPSI. It's actually not even possible to reproduce the 262mod1 2680 ft/s out of a 16" at 55KPSI with canister powders. You can get close, but my bet is the military round is simply slightly over their self imposed pressure limit. I'm actually throwing the 5.56 a bone here - if forced to meet the same standards I imposed on the 6x45 (temp stability, 55KPSI) there's barely a route to hit 2600 ft/s.

In an apples to apples compare, the 6x45 will always win a long range energy comparison, and it's really not particularly close.

 

[lysanderxiii]

What's funny, is the figure has stayed the same since 'Nam while our tactics drastically changed. I'll bet the pounds of high explosive per enemy casualty (assuming a count is even possible given the whole 'red mist' aspect) has steadily decreased since WWII, though, while the consumption of fuel per casualty has been filling the void . The real message may be that infantry rifles simply aren't a huge driver of strategic results, and therefore aren't effected very much themselves by strategic changes. Which has been kind of the consensus reached by anyone who's job is to determine whether a cartridge swap is worthwhile, and it's apparently no one outside DARPA with the LSAT crew.

Ta-da! we have a winner!

Art, tell him what he's won....

 

[lysanderxiii]

If you want down range performance, both .223 and 6x45 have to go to the heavy bullets but there's substantial limits with .223. For example, the.223 77gr SMK has a G1 BC of .362 in the middle velocities, whereas the 95gr .243 is .460.

What is the maximum ordinate of a 95 gr .243" at the maximum velocity you can push it to in a 6x45 when zeroed at various ranges?

The reason you want a flat trajectory is range estimation in combat is +/- 75% to 80%

With a combat zero the M4 is going to hit a man-sized target with a COM aim out to 400 meters.

 

[Llama Bob]

I'm pretty sure you're intentionally avoiding the point. The purpose of a 6x45 95gr SMK load isn't to shoot flat, any more than the purpose of of Mk262mod1 is to shoot flat. They're long range loads. But you knew that, right?

 

[eastbank]

my 40x 6mm-47 barrled by robert w hart & son will kick a 87gr hornady V-max((B.C. 400) at a honest 2800 fps and shoots little bug holes. and i think the 6mm-45 would be very close to the 6mm-47. eastbank.

 

[Llama Bob]

Incidentally, if you want a flat shooting comparison load for 6x45, it can drive a 65gr Berger at 2970 ft/s out of a 16" barrel while staying within 55K/temp insensitive limits. The G1 BC on that bullet is .280. Compare that to M193 at 3050 with a BC of .243. You'll see that the maximum PBRs of the two are exactly the same.

Once again, the .223 fails to find something it's good at. But we knew that, because there's nothing it's better than the 6x45 at

 

[VoodooMountain]

I don't think you are looking at this objectively llama.

The ONLY thing a 6x45 could do that the 223 cannot is launch a heavier bullet, and not by much. 77 vs 100 gr. Both rounds use the same case. If the 6mmx45 launches a 65gr pill at 2970 fps then the 223/556 can do the same or at worst within 3-5 percent.

You ignore the fact that there is a partition for 223 and that all partitions have the same listed velocity range through nosler and entirely negate that the 60gr 223 bullet has a significantly higher velocity than the 6mm 95 gr. This is interesting for the reasons I have posted in my other posts and because you state it makes the 6mm good to 350 yards before expansion fails which you say equates to an effective deer gun at that range.

It seems you are overlooking the very basics of terminal ballistics as well. Expansion doesn't make a clean kill. There is MUCH more going on.

Our military is restricted to ball ammo and thus uses velocity to compensate and cause bullet disruption and hydrostatic shock. Switching to 6mm doesn't change this.

An intense amount of research and development has gone into engineering 223 projectiles because it is such a widely used round. This has made the civilian market flush with many great options for just about anything up to and including deer hunting.

6mm bullets, by and large, are designed around the notion they will be used in a 243 Winchester or 6mm Remington which run at significantly higher velocities than the x45. Obviously, some bullets are better suited to lower velocity than others.

The 6x45 heaviest bullet is basically 100 gr. It pushes this bullet at the same velocities as the 7.62x39 or 300 b.o. Pushes a 150 gr. bullet.
So you have the slow velocities of the x39 without any of the barrier penetration capabilities.

That is fine that you March to a different beat or that you don't care for the 223. I can understand that. Necking up a 223 case to 6mm won't overcome anything, really.

The 6mmx45 isn't best nor does it beat the 223/556 in everything.

 

[lysanderxiii]

I'm pretty sure you're intentionally avoiding the point. The purpose of a 6x45 95gr SMK load isn't to shoot flat, any more than the purpose of of Mk262mod1 is to shoot flat. They're long range loads. But you knew that, right?

I think you're missing the point as to one reason why they picked, a stuck with the cartridge they did... a flat trajectory.

Mk262 in pretty close to M855, as far as trajectory goes.

And I was asking "What is the maximum ordinate of a 95 gr bullet pushed to the limit of a 6x45 case?" I am not sure.

 

[Llama Bob]

The ONLY thing a 6x45 could do that the 223 cannot is launch a heavier bullet, and not by much.

That's false. The fundamental additional capability is that it can shoot bullets suitable for the taking of medium game (including humans) as opposed to varmints. There are no such bullets for .223, despite all the pretending going on.

Assuming you're not planning to fight the woodchuck army, that's a very large advantage.

 

[lysanderxiii]

Incidentally, if you want a flat shooting comparison load for 6x45, it can drive a 65gr Berger at 2970 ft/s out of a 16" barrel while staying within 55K/temp insensitive limits. The G1 BC on that bullet is .280. Compare that to M193 at 3050 with a BC of .243. You'll see that the maximum PBRs of the two are exactly the same.

Once again, the .223 fails to find something it's good at. But we knew that, because there's nothing it's better than the 6x45 at

M193 is obsolete in the realm in which you started this thread, why compare to it?

Compare it to M855/M855A1, or any other current round, and use a 14.5 in barrel.

 

[Llama Bob]

The 6mmx45 isn't best nor does it beat the 223/556 in everything.

And yet no one has been able to find anything the .223 is better at, while it's clear what the 6x45 is better at. Wonder how that happened...

 

[Llama Bob]

M193 is obsolete in the realm in which you started this thread, why compare to it?

Compare it to M855/M855A1, or any other current round, and use a 14.5 in barrel.

M855 shoots less flat than M193. You're just handidicapping the .223 even more

 

[mshootnit]

Hornady 70 gr. 24 cal will open up faster than the Sierra offering. Sierra holds together a little better; must be the jacket.

 

[VoodooMountain]

And yet no one has been able to find anything the .223 is better at, while it's clear what the 6x45 is better at. Wonder how that happened...

Do you not understand what I post or do you just ignore it?

These 2 chamberings are VERY similar. The 6x45 can launch a bullet that is 20gr heavier.....that's it. Not exactly better at anything just different.

If you like the round, that's fine. It doesn't make everyone else is wrong. Not by a looooong shot.


Oh...and the 223 would be 20gr lighter to carry if you want to nit pick.
There are many more bullet options than 6mm and they are designed to work for the velocity of the 223/556 as opposed to your 6x45.
It's also cheaper.

This has become ridiculous.

 

[lysanderxiii]

There is a 6mm x 45 can be an improvement over 5.56mm NATO, but not the 6mm x45 Wildcat you are talking about seen today.

This 6mm x 45, the 6mm SAW:



The 6mm x 45 round designed by Frankford back in the early 1970s to ultimately replace both the 5.56mm and the 7.62mm. Unfortunately, it fell afoul of NATO standardization.

(Oh and wikipedia not withstanding, the aluminum cases did not have a propensity to "catch fire", they suffered from "burn-through", which has nothing to do with catching fire. It is when a crack develops in the head, and the hot, high pressure gas quickly erodes the aluminum crack to a much larger size, allowing dangerous amounts of gas to escape. The problem is in order for the aluminum to strong enough, it has to be hard, but when harden, it becomes brittle. And, even hard aluminum is easily cut by high pressure gas.

Curiously, this isn't a problem with larger (20 mm and larger) cartridges. But then larger cartridges can have proportionally thicker head webs, even though they can operated at higher chamber pressures.)

(And while they don't talk about it, I'll bet this cartridge really pissed off the British. 6mm SAW was about the same, performance-wise as the British .280 "Optimum" of the early 1950s, a step down from 7mm "Second Optimum" and a lot less powerful that 7mm "Compromise", all of which were nixed by the US as "not powerful enough"....)

 

[lysanderxiii]

Your initial post gave me the impression that this was to be a discussion of the military potential of a certain round. Not a wick-measuring contest of "who cartridge is 'better'", whatever that means.

If that is the case, then compare apples-to-apples, not apples-to-last years oranges.

Since the case is the same, the volumes are comparable, so weight vs velocity are going to be really close, and longer skinny bullets generally have higher BCs, they will retain velocity better. making for better longer range performance.

 

[ugaarguy]

The advantage is substantially improved terminal ballistics. We're on the 4th attempt to re-design the .223, and it still sucks. Always has, always will.

The "redesigns", as you call them, are just changes based on expected mission requirements. M193 works as designed against targets not wearing body armor. M855 was brought about because we wanted to be able and penetrate Soviet soft body armor, and we sacrificed terminal performance on unarmored targets to get that penetration. It's no different than switching from factory loaded JHPs for self defense to boutique or hand loaded heavy hard cast bullets for penetration on heavier game like hogs with a .357 Mag revolver.

Regardless of bullet restrictions the .223 is a varmint cartridge. It can never get away from that - too small and too light to be suitable for CXP2 game (or humans of the same size). It's not legal for CXP2 game in many places either.

Repeating that false opinion over and over again won't make it true. In the places where .223 is legal deer it works quite well. I've seen large bucks cleanly killed with 55gr Nosler Ballistic Tips and similar bullets with the shot placed just behind the shoulder. It turns the heart and lungs into something resembling "strawberry soup" as a friend described it.

I also have a close friend who's retired USAF Pararescue. He's treated plenty of gunshot wounds and seen in person and in postmortem photos what M193 ball will do to human flesh. He has no doubts that if you're not wearing armor to stop it, if you're hit COM with M193 you have an extremely low chance of survival.

 

[barnbwt]

And yet no one has been able to find anything the .223 is better at, while it's clear what the 6x45 is better at.

1) Lighter weight
2) Lower recoil

Both are *kind of* important for volume fire & maneuverability tactics. If you think those tactics are "wrong," I suggest steering discussion thataway, rather than imagining a role for your pet round in the present reality of infantry use.

Wonder how that happened...

I can tell you what happened; you have consistently ignored a lot of counterpoints to your arguments in favor of restating your own.

This has become ridiculous

It was always thus

TCB

 

[barnbwt]

The fundamental additional capability is that it can shoot bullets suitable for the taking of medium game (including humans) as opposed to varmints. There are no such bullets for .223, despite all the pretending going on.

"Fundamentally," your argument is less than half a millimeter...less than half a millimeter! in bullet diameter, and no other significant changes to the cartridge. And this is supposed to drastically alter performance. Please.

At least with Grendel, there's both more powder & bullet length to work with, even if this does raise other issues with the AR platform, so it can be argued the end result is 'different' enough to be worth mentioning. Same goes for 300 Blackout, since the bullet/powder ratio is so different. The 6x45 is so nearly identical to 5.56x45, that the next closest cartridge to 5.56x45 is 223!*

*someone confirm this; either 223 or 222 RemMag, unless there's a 5.8x45 or something out there

 

[txblackout]

I'm not saying marksmanship has evolved or devolved or anything else. I'm saying if it takes you 100,000 OR 250,000 rounds to get a kill, it can't be called marksmanship. Get that number down to say 20 and we can talk.

250,000 includes training rounds.