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

[Llama Bob]

6x45 is pretty much everything people wish .223, 6.8SPC, 6.5SPC and all the other high velocity small bore AR15 wildcats could be.

6.5x45 out of a 16" AR:
- Drives a 100gr partition or similar deer/sheep/antelope/hogs hunting bullet at about 2450 ft/s, which keeps it in the partition's operating velocity window out to 370 yards (with my atmospherics - your results will depend on temp and elevation).

- Drives a 95gr SMK at 2520, making it a trajectory duplicate for M118LR out of a 16" gas gun. This is enough to stay supersonic to 1000y (again, my atmospherics).

- Drives 55gr varmint bullets in the 3200-3400 range depending on bullet.

So basically you get vastly improved terminal performance both on game and on humans compared to .223. That partition load is suitable for all CXP2 type game out to 350y. You get the same trajectories as .308 (in the same length guns), and retain the varmint capabilities of .223. It would also be very possible to produce military armor defeating loads as needed given the high velocities attained with light bullets. The brass is formed simply by taking a .223 LC case and running it through a sizing die. The only component that changes on the AR platform when moving from .223 is the barrel. From a technical perspective the 6x45 is all upside, no downside.

Face it, the AR15 is simply chambered in the wrong round. It's sad we're too far down the road to fix it.

 

[VoodooMountain]

The 223/556 chambering has more to do with the amount of ammo a soldier can carry and with the necessity of fmj bullets high velocity is useful for its terminal effects to compensate for bullet design.


And I have to strongly disagree with a 243 bullet moving at 2450 fps being good for any cxp2 game out to 350ish yards because it definitely isn't. A 243 win will get to about 3000fps and is good for deer.

You have essentially neutered the ballistics to work in the gas gun and you end up launching 100gr at about the same velocity the 762x39 can launch 150 grains but you don't have the penetration or barrier defeating capabilities of the heavy bullet out of the x39.

So to compensate for this you use lighter bullets in the 55gr range and launch these at 3200 fps or roughly about the same velocity as 556 can.

So I guess I have to say the 6mm may be one of the worst choices, but it's my opinion of course.
You don't increase bullet size very much, bullet weights with good terminal effects are again a wash, capacity would likely suffer to some degree I suppose, and there is the cost of converting your system.

 

[cougar1717]

I like the idea of the 6x45, but wouldn't it have the same problem with the magazine and chamber throat limiting the OAL of the heavy bullets?

 

[Skyshot]

I like the 6x45 idea and even the 25x45 idea. I don't think it's going to become a 300 yard deer hammer though. But I think it would make dandy chambering for the AR. And would be a terrific 200 yard whitetail load. More so than the .300 blkout, which I just can't feel the vibe for. But I guess the latest fashion for suppressors and overwhelming marketing is pushing the .300.

 

[jmr40]

And I have to strongly disagree with a 243 bullet moving at 2450 fps being good for any cxp2 game out to 350ish yards because it definitely isn't. A 243 win will get to about 3000fps and is good for deer.

A 243 with modern bullets will do anything a 30-06 used to be able to do. As a military round shooting FMJ, the advantage 243 or 6mm would offer is marginal.

https://www.youtube.com/watch?v=hY0w1c-gf18

A 6mm cartridge out of an AR style rifle might offer some advantages over 223 as a hunting cartridge on game larger than deer. But as a military round any advantages are too small to be worth the change. Had it been adopted 1st I'd agree it might be a better option. Not enough difference to change at this point unless a completely different weapons system is also going to replace the AR platform.

 

[Llama Bob]

The 223/556 chambering has more to do with the amount of ammo a soldier can carry and with the necessity of fmj bullets high velocity is useful for its terminal effects to compensate for bullet design.

There is essentially no weight difference between 6x45 and .223

And I have to strongly disagree with a 243 bullet moving at 2450 fps being good for any cxp2 game out to 350ish yards because it definitely isn't. A 243 win will get to about 3000fps and is good for deer.

OK, you go ahead and disagree and take it up with Nosler (and lots of dead deer). A 100gr 6mm partition at anything over 1800 ft/s on impact will do just fine on any CXP2 game.

 

[Llama Bob]

A 243 with modern bullets will do anything a 30-06 used to be able to do. As a military round shooting FMJ, the advantage 243 or 6mm would offer is marginal.

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. Unless of course we go to war with the woodchucks, in which case it'd be exactly the right medicine.

 

[Llama Bob]

I like the idea of the 6x45, but wouldn't it have the same problem with the magazine and chamber throat limiting the OAL of the heavy bullets?

Chamber throat you can cut however you want. All the numbers in the OP assume a 2.26 AR15 magazine OAL. No problems. Heavier than a Berger 105, you might have problems...

 

[Coop45]

There is essentially no weight difference between 6x45 and .223

OK, you go ahead and disagree and take it up with Nosler (and lots of dead deer). A 100gr 6mm partition at anything over 1800 ft/s on impact will do just fine on any CXP2 game.

5.7 pounds per 1000 is a big difference over 62 gr 5.56mm to me. Unless of course you can poop an ammo resupply when the wolf is at the door with mucho hundred of his pack mates. That's almost 100 rds of gun ammo. The difference with 55gr would be even more.

 

[FL-NC]

The 5.56 round (especially some of the newer loads developed for the military) is more than adequate for the job it is intended to do, and is a solid NATO standard.

 

[lysanderxiii]

6x45 is pretty much everything people wish .223, 6.8SPC, 6.5SPC and all the other high velocity small bore AR15 wildcats could be.

6.5x45 out of a 16" AR:
- Drives a 100gr partition or similar deer/sheep/antelope/hogs hunting bullet at about 2450 ft/s, which keeps it in the partition's operating velocity window out to 370 yards (with my atmospherics - your results will depend on temp and elevation).

- Drives a 95gr SMK at 2520, making it a trajectory duplicate for M118LR out of a 16" gas gun. This is enough to stay supersonic to 1000y (again, my atmospherics).

- Drives 55gr varmint bullets in the 3200-3400 range depending on bullet.

So basically you get vastly improved terminal performance both on game and on humans compared to .223. That partition load is suitable for all CXP2 type game out to 350y. You get the same trajectories as .308 (in the same length guns), and retain the varmint capabilities of .223. It would also be very possible to produce military armor defeating loads as needed given the high velocities attained with light bullets. The brass is formed simply by taking a .223 LC case and running it through a sizing die. The only component that changes on the AR platform when moving from .223 is the barrel. From a technical perspective the 6x45 is all upside, no downside.

Face it, the AR15 is simply chambered in the wrong round. It's sad we're too far down the road to fix it.

Not really.

The thing about .223/5.56 is the nice flat trajectory.

What was missed was not using the Springfield/Frankford designed "Improved" .222 Remington, aka, .222 Remington Magnum.

That little extra case volume would have allowed heavier bullets at the same velocities as today, while not making the chamber pressure to not get to proof levels.

 

[Llama Bob]

The 5.56 round (especially some of the newer loads developed for the military) is more than adequate for the job it is intended to do, and is a solid NATO standard.

If it was adequate they wouldn't have to keep redesigning it. It's specifically because if its inadequacy that 5.56 is now on the 4th redesign of the basic ball round.

 

[Llama Bob]

Not really.

The thing about .223/5.56 is the nice flat trajectory.

Well, that's an interesting theory since the military has been busily increasing the projectile weight and decreasing the velocity (and thus producing a more looping, but higher energy trajectory) in an attempt to fix the external and terminal ballistics.

 

[VoodooMountain]

If it was adequate they wouldn't have to keep redesigning it. It's specifically because if its inadequacy that 5.56 is now on the 4th redesign of the basic ball round.

I would say that has more to do with bullet restrictions for our armed services.

Ironically, you and I strongly disagree about the lethality of a 100gr bullet moving at 2400fps out to 350 yards being good medicine but I have to point out how well the 223 can hold its own for a variety of tasks (including deer) when a Proper bullet is used out to 150 or so yards. Bullets not allowed for warfare use.

I hate to nitpick but simply because a bullet expands doesn't mean it's a proper choice. Energy is low, no hydrostatic shock , rainbow trajectory, inconsistent bullet performance, etc. To put it another way, your logic would argue that a 30/30 is at least 350 yard deer gun as it has the same velocity but with a bullet 50 percent heavier.

Shooting a deer at that distance with that slow of a projectile isn't a very good idea unless you place that bullet Exactly where it needs to go in which case Any bullet of any weight would be equally effective.

 

[Llama Bob]

I would say that has more to do with bullet restrictions for our armed services.

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.

I hate to nitpick but simply because a bullet expands doesn't mean it's a proper choice. Energy is low, no hydrostatic shock , rainbow trajectory, inconsistent bullet performance, etc. To put it another way, your logic would argue that a 30/30 is at least 350 yard deer gun as it has the same velocity but with a bullet 50 percent heavier.

Actually, no, you've totally failed to understand my logic. Show me a .30-30 load that can keep it's bullet within the manufacturer's intended operating window at 350 yards, and we can talk. Only there is no such load, because all .30-30 bullets have horrible BCs. The 6x45 can do it no problem. And I can say from experience that the 100gr partition does exactly what you'd want at the low end of its designed operating velocity range: it expands and almost always gives through-penetration, resulting in a fast drop and massive blood trail.

Shooting a deer at that distance with that slow of a projectile isn't a very good idea unless you place that bullet Exactly where it needs to go in which case Any bullet of any weight would be equally effective.

It's perfectly functional and a designed application of the bullet. Just ask call up Nosler and ask them.

 

[Haxby]

6X45 has been around for 50 years. Guess it didn't really catch on.

 

[Llama Bob]

6X45 has been around for 50 years. Guess it didn't really catch on.

Very true, and it's a profound shame. It was marketed to the wrong crowd (benchrest) where it was suitable, but eventually surpassed. The really useful application was as an AR upgrade. There just weren't enough ARs in civilian circulation back when it was new to get traction.

Of course the place it SHOULD have caught on was doing due diligence on the service caliber, where they absolutely should have swept the projectile diameters to determine what was best, and would have discovered that 6x45 was superior for all applications. But the .223 adoption was not the kind of effort where anyone was doing any due diligence, or we never would have adopted a varmint cartridge for shooting much-bigger-than-varmint humans.

 

[Dr.Rob]

We 'missed it' because back in 1980 or so the Army looked at it (part of the SAW program) and decided it wasn't worth rechambering/replacing every rifle and cartridge in the standing inventory.

 

[adcoch1]

Llama Bob, your intense dislike for 223 is the only real detractor from your argument. 223 doesn't suck. Its a great cartridge for targets and accuracy. 223 ball ammo sucks. 6X45 is better at almost all hunting chores than 223/5.56, but does weight more by enough to take away some of the advantages of 5.56 over, say, 7.62x39. The problem is that ball 6x45 wouldn't be very much better at all. In the civilian world though, and largely in the LEO world, I agree that in the AR15 platform 6x45 would have been a great improvement over 223/5.56.

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[Llama Bob]

Llama Bob, your intense dislike for 223 is the only real detractor from your argument. 223 doesn't suck. Its a great cartridge for targets and accuracy. 223 ball ammo sucks. 6X45 is better at almost all hunting chores than 223/5.56, but does weight more by enough to take away some of the advantages of 5.56 over, say, 7.62x39. The problem is that ball 6x45 wouldn't be very much better at all. In the civilian world though, and largely in the LEO world, I agree that in the AR15 platform 6x45 would have been a great improvement over 223/5.56.

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I don't have an intense dislike of .223. I have a dislike of using a varmint round on medium-game sized targets. If you want to shoot paper, or woodchucks, or as a recoil-adverse women and kids compromise rifle it's fine.

The weight difference is trivial and is a made up complaint. .223 gets heavier when you increase the BC too, but I don't hear anyone bitching about all that ultra-heavy M262Mod1.

 

[Llama Bob]

We 'missed it' because back in 1980 or so the Army looked at it (part of the SAW program) and decided it wasn't worth rechambering/replacing every rifle and cartridge in the standing inventory.

Of course. If there's one thing you can count on the military for, it's that once they've made the wrong decision they will double down on it because that's the way things have always been done

 

[lysanderxiii]

You do realize that they have also redesigned the 7.62 and Caliber .50 AP rounds a few times....

The M855 still has a flatter trajectory than M118LR.....

Oh, and if we were going to start with a blank sheet of paper, the right choice would be around 7mm.

That way you could get rid of 7.62mm in the GP and medium machine gun.

 

[adcoch1]

7mm08 anyone?

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[Llama Bob]

You do realize that they have also redesigned the 7.62 and Caliber .50 AP rounds a few times....

Yes, although not due to lack of external or terminal performance. The .7.62 accuracy load (designated M118/M118SB/M118LR/M316Mod0 and a few less formal things) has been pretty much the same since the 60s. There's just been some turnover in bullet and powder suppliers and some modest increases in BC as we learned how to make better match bullets.

 

[Llama Bob]

The M855 still has a flatter trajectory than M118LR.....

Your point being what? You can get the same flat trajectory in 6x45 if you want to similarly decrease the BC.

.223 has literally no advantages. It's the mistake that won't go away