Building a 6mm ARC Upper

[Omni]

I think the new 22 ARC is the 'final form' for these cartridge derivatives in the AR platform. You get maximum velocity for the powder capacity without the bullet 'setback' issue the heavier bullets can have in the semi-auto platform. 22 ARC I think is going to be what 224 Valkyrie wanted to be when using long heavy (80-95gr) bullets, but can still shoot light .224 bullets if desired and come close to .22-250 performance.

 

[Nosferatu]

The only difference I see between the two calibers is the 6ARC excels with the lighter faster bullets.

IIRC, sectional density is where the 6mm outshines the 6.5. If I'm shooting it at an animal, that's what I want. The added speed lets the copper bullets I like to use optimize their effectiveness.

Im uncertain about a bolt action advantage with the Grendel if the chambers are both to sammi spec but I do know the heavier bullets in the Grendel have to be seated too deep inside the case losing velocity potential. I suspect a long throated bolt gun would make the Grendel really stand out with the heavier options....

Probably. I got this to become a better shooter, so the differences for me are minimal. I like having a good factory load for this gun.

Ive heard the Hornady Black is the most accurate factory Grendel ammo, but I haven't tried it since I handload for mine.

Can't speak to that because I stopped shopping after shooting the Black. I'm sure some of the boutique brands can top it, but for the money, Black is hard to beat.

 

[DirectDrive]

so, why the 6mm ARC over the 6.5 Grendel when they use the same case, bolt and magazine in the AR15 platform?
the 6.5 Grendel is a well establish round with a wide variety of bullets and factory ammo
a 6.5 Grendel can be used to targets out to 1000 yrds and hunting out passed 300 yrds in just a 16" bbl
my .264 LBC will do anything I need

View attachment 1869987

Grendel can't drive the high BC 6.5 pills.
6mmARC does a better job driving the high BC pills.

22ARC may be the star of the whole family.

 

[rjmt]

Grendel can't drive the high BC 6.5 pills.
6mmARC does a better job driving the high BC pills.

22ARC may be the star of the whole family.

what is your use that you need the higher BC
paper targets don't care
I agree that it's hard to beat Hornady Black on paper

 

[Ben B.]

Long range steel cares.

 

[rjmt]

Yeah, no mainstream, super popular 6.5 Grendel for me, I want to blaze a trail with the edgy, wildcat that no one knows about, the 6ARC…

https://www.handloadermagazine.com/6mm-arc

 

[DirectDrive]

Yeah, no mainstream, super popular 6.5 Grendel for me, I want to blaze a trail with the edgy, wildcat that no one knows about, the 6ARC…

Not a scary wildcat.
6ARC was SAAMI approved in June 2020

But wait !
There's another one !
22ARC SAAMI approved !

There's more !
22 Creedmoor SAAMI approved !
The big dog needs to eat.

 

[Nosferatu]

I want to blaze a trail with the edgy, wildcat that no one knows about, the 6ARC…

https://www.handloadermagazine.com/6mm-arc

Not a scary wildcat.
6ARC was SAAMI approved in June 2020

@Ben B. - You caught two fish on that worm. Nicely done!

 

[Ben B.]

@Ben B. - You caught two fish on that worm. Nicely done!

 

[DirectDrive]

@Ben B. - You caught two fish on that worm. Nicely done!

Nah, he's lookin' at the inside of the boat !
And tryin' to grow an adipose !

 

[rjmt]

Grendel can't drive the high BC 6.5 pills.
6mmARC does a better job driving the high BC pills.

22ARC may be the star of the whole family.

I built my rifle back in 2016, the .264 LBC was a wildcat cartridge
my rifle is based around a BHW 20" bbl with a Grendel 2 bolt and P3 riffling
the .264 LBC chamber is based around the Hornady 123 bullet with a BC of .510
but IF I hand loaded, I can load a Hornady 130gn VDL at a BC of .552 and still fit in .264 chamber and an Grendel mag
the best BC I can find for a Hornady bullet for 6mm is a 107 gn bullet with a BC of .547
can long range steel plates really tell the difference?

 

[rjmt]

I built my rifle back in 2016, the .264 LBC was a wildcat cartridge
my rifle is based around a BHW 20" bbl with a Grendel 2 bolt and P3 riffling
the .264 LBC chamber is based around the Hornady 123 bullet with a BC of .510
but IF I hand loaded, I can load a Hornady 130gn VDL at a BC of .552 and still fit in .264 chamber and an Grendel mag
the best BC I can find for a Hornady bullet for 6mm is a 107 gn bullet with a BC of .547
can long range steel plates really tell the difference?

and back in the Day (1992), when i was reloading 5.56 for my colt AR for NRA HP competition,
for 500 yrds, i loaded SMK 62 gn hot with 4895 and adjusted my die for a couple mm longer than an AR mag would hold
since 500 yrds was slow fire, I loaded the bullets longer than an AR mag would hold by about 2mm
rolled each round in manually and hit the bolt release
was using IMI brass and never observed over pressure on the cases, but only reloaded the cases 10 times
why can't one do the same for 6.5 if your shooting long range steel targets?

 

[Omni]

I built my rifle back in 2016, the .264 LBC was a wildcat cartridge
my rifle is based around a BHW 20" bbl with a Grendel 2 bolt and P3 riffling
the .264 LBC chamber is based around the Hornady 123 bullet with a BC of .510
but IF I hand loaded, I can load a Hornady 130gn VDL at a BC of .552 and still fit in .264 chamber and an Grendel mag
the best BC I can find for a Hornady bullet for 6mm is a 107 gn bullet with a BC of .547
can long range steel plates really tell the difference?

The 6mm ARC would have at least a 200fps velocity advantage with similar high BC projectiles.

and back in the Day (1992), when i was reloading 5.56 for my colt AR for NRA HP competition,
for 500 yrds, i loaded SMK 62 gn hot with 4895 and adjusted my die for a couple mm longer than an AR mag would hold
since 500 yrds was slow fire, I loaded the bullets longer than an AR mag would hold by about 2mm
rolled each round in manually and hit the bolt release
was using IMI brass and never observed over pressure on the cases, but only reloaded the cases 10 times
why can't one do the same for 6.5 if your shooting long range steel targets?

If your plan is to build a precision 6/6.5mm long range rig I don't know why you would purposely plan to single feed a semi-auto instead of just using a more accurate bolt action with magazines that fit longer COAL?

 

[rjmt]

The 6mm ARC would have at least a 200fps velocity advantage with similar high BC projectiles.


If your plan is to build a precision 6/6.5mm long range rig I don't know why you would purposely plan to single feed a semi-auto instead of just using a more accurate bolt action with magazines that fit longer COAL?

because one was trying to get the best trajectory out of a rifle specified for NRA HP competition
today, I just use factory Hornady ammo for punching holes in paper or ringing steel plates

and again I ask, do paper or steel targets know the difference in 200 fps or a BC of .510 to .547?

each shooter has their preference, but I don't see enough difference to re-barrel my .264 LBC for 6mm ARC

NOTE: it only takes me 15 min to re-barrel an AR, it's no big thing if I wish to do so, only the cost of a barrel

 

[Omni]

because one was trying to get the best trajectory out of a rifle specified for NRA HP competition
today, I just use factory Hornady ammo for punching holes in paper or ringing steel plates

and again I ask, do paper or steel targets know the difference in 200 fps or a BC of .510 to .547?

each shooter has their preference, but I don't see enough difference to re-barrel my .264 LBC for 6mm ARC

NOTE: it only takes me 15 min to re-barrel an AR, it's no big thing if I wish to do so, only the cost of a barrel

I guess there's no point to 6.5 Creedmoor. It shoots 6.5 Grendel bullets faster, but the targets can't even tell the difference!

 

[rjmt]

I guess there's no point to 6.5 Creedmoor. It shoots 6.5 Grendel bullets faster, but the targets can't even tell the difference!

I was working in Las Vegas about 6 years ago and the 1000 yrds shooters there were switching from .308 to 6.5 Creedmore for the ballistics at 1000 yrds
I guess if you have access to a 1000 yrd range, and wanted to use an AR 15 platform, a 6mm ARC would make sense
but - I don't
for 300 yrds, my .264 LBC is just fine
but for 1000 yrds, I would still use my rem 700 in .308 with LC M118LR ammo

 

[Lazyfaire]

6mm ARC was developed by Hornady for use by the military. 6 ARC is smaller and lighter than 5.56 allowing the soldier to carry more ammo farther. It shoots flatter, hits harder at distance, and goes trans-sonic past 1000. While it will shoot 1000 yards its best use would be in the 600-800 yards. The test military rifles were Barrett ARs with Proof CF barrels at a weight of under 6.5lbs. Test units were never identified (spec ops of some sort). Have never seen anything as to its viability in the field. Would rather carry this than a .308

 

[Sxsnuf]

A Grendel upper magically appeared in my safe recently. Now that it's there, I've had to find something to feed it. The cartridge sort of intrigues me, though I don't really know why. It's no great shakes, BCA side charger with a 20" SS heavy barrel.
It's one more toy that I haven't had time to enjoy.

 

[Omni]

6 ARC is smaller and lighter than 5.56 allowing the soldier to carry more ammo farther.

Everything you said is true except this. The 6 ARC cartridge uses larger brass, bullets and more powder than 5.56. Maybe you meant 308?

 

[Lazyfaire]

Everything you said is true except this. The 6 ARC cartridge uses larger brass, bullets and more powder than 5.56. Maybe you meant 308?

Nope. Not true. A 308 is longer than 6mm ARC
.308 weighs 24 grams
6mm ARC weighs 16 grams