6mm ARC velocities with 18" barrel and light bullets?

[uncle fester]

I built my own AR upper with a 20" Shaw barrel. I liked it so much, I bought a cheap Savage Switchback bolt action in 6ARC with a 24" barrel. It is my favorite rifle to shoot paper targets. 3/4 MOA bone stock but for two mods: (1) removed muzzle break as unnecessary and (2) dropped it in a chassis.

My plan is to see how many rounds it takes me to burn out that barrel before I replace it with a nicer barrel.

 

[MittenMan]

I am thinking about putting together a 6mm ARC on a AR platform for night hunting coyotes with 55-65 grain bullets and wanting to see what real world velocities everyone is getting with a similar setup before I go forward with it. Does anyone run the light bullets in this cartridge with a shorter barrel (16-20")? If so, what velocities are you getting? I know the cartridge was designed for shooting the heavies (90-108 grain) at long range and that is another reason I am leaning towards it, because of the versatility of it. I am hoping the 6mm ARC running 55-60 grain bullets will have a higher velocity than a similar setup 223 AR running 55-60 grain bullets.

Shooting 65 and 75 grain V-Max in a Faxon fluted and getting sub moa at 100 using 8208 and R15. Getting best groups with 8208 but R15 is very close. Seated bullets slightly longer than book. I’m right at max with Hornady data and ejected cases are right there with the factory stuff.

 

[Rocketvapor]

The 6-ARC beats the 5.56 by a bunch, a 224V by some, and the 22 Nosler by a little.
Bolt gun loads/pressure make it a strong round. Gas Gun/Commercial loads, not so much.

The BIG selling point for the 6-ARC is:
The cartridge makes use of 6 mm (.243) bullets, which are known for their high ballistic coefficients due to the high sectional density with less drag and better energy retention at extended ranges. With the release in 2020, Hornady also launched three factory loads with 103, 105 and 108 gr (6.7, 6.8 and 7.0 g) bullet weights and advertised G1 ballistic coefficients of .512, .530 and .536 respectively.

Here are some points from the JBM calculator.
80F, 20' elevation, 50%, AR sight height of 2.7".
Drop and 10MPH drift @ 1000 yards.
All bullets calculated with a muzzle velocity of 2750 which just about anything bigger than a 223Rem can do.
The 110 SMK or A-Tip are great heavy weight bullets for the ARC.
Compare the 95 grain SMK in 6mm and .224" @ 2750fps.


CFE223 and LeverEvolution give the best velocities for heavy bullets in the 6-ARC.
Hornady load data shows 2740 fps in a 24" GAS GUN (2815 fps with a 28" barrel), and 2850 fps in a 24" BOLT GUN, (LeverEvolution) for the 108-110 grain.

Sorry for being off topic. The thread was about light bullets in an 18" barrel.

 

[Beiruty]

How about 6-CrdM in AR-10 for is the extra powder worth the +250fps?

 

[243Mendoza]

The 6-ARC beats the 5.56 by a bunch, a 224V by some, and the 22 Nosler by a little.
Bolt gun loads/pressure make it a strong round. Gas Gun/Commercial loads, not so much.

The BIG selling point for the 6-ARC is:
The cartridge makes use of 6 mm (.243) bullets, which are known for their high ballistic coefficients due to the high sectional density with less drag and better energy retention at extended ranges. With the release in 2020, Hornady also launched three factory loads with 103, 105 and 108 gr (6.7, 6.8 and 7.0 g) bullet weights and advertised G1 ballistic coefficients of .512, .530 and .536 respectively.

Here are some points from the JBM calculator.
80F, 20' elevation, 50%, AR sight height of 2.7".
Drop and 10MPH drift @ 1000 yards.
All bullets calculated with a muzzle velocity of 2750 which just about anything bigger than a 223Rem can do.
The 110 SMK or A-Tip are great heavy weight bullets for the ARC.
Compare the 95 grain SMK in 6mm and .224" @ 2750fps.
View attachment 1368746

CFE223 and LeverEvolution give the best velocities for heavy bullets in the 6-ARC.
Hornady load data shows 2740 fps in a 24" GAS GUN (2815 fps with a 28" barrel), and 2850 fps in a 24" BOLT GUN, (LeverEvolution) for the 108-110 grain.

Sorry for being off topic. The thread was about light bullets in an 18" barrel.

There is theory and there is practice; the above loads will shear a lug eventually in a AR15. If you use a bolt gun, I would go with the 6BR.

 

[Raptor]

I have an 18" Proof that was converted from a 24" shot out 6mm Creedmore off of my RPR. I shot the throat out of it and just had it laying around, so I gave it to my smith and had him cut the ass end off and make me an ARC barrel. It was a 1-8 twist and I started off shooting factory ammo and it shot well but I actually wanted to shoot the 80 to 90gr bullets. I think that is the best compromise for this caliber. It shoots the 80 and 90gr Bergers in around a .5 for 5 shot groups. I tried some 75grVMAXs and they sucked. Digging around the other day I found an old box of 70 NozBTs so thought I would try them. I loaded up some LVR, 8208 and H335. 5 shot groups were .592 with 8208 and .462 and .465 with the LVR and H335. LVR was fastest at 3100fps flat and the other two were close with from 3080 to 3090fps. I then tried CFE and something else. Can't remember right now. They didn't shoot all that great. I then shot them all at 300yds and the LVR was the star with 5 shot groups being in the .7s to .8moas and 3 shot groups in the .5moa range. I then shot it all the way out to 700yrds and got 3.75" to 4" 3 shot groups at 700yds...

 

[rickt300]

Well my rifle is a 6 Grendel but I bought it hoping light bullets will work and they did. I actually have two almost identical rifles. Using BLC2 and the 58 grain VMax I easily get less than MOA groups. My rifles have BHW barrels of 20 inches in length and 1-8 twists. I bought a bunch of those bullets as factory seconds from Midway mostly to fireform new Starline Grendel brass into 6 Grendel and accuracy has been excellent. Several raccoons and no coyotes yet. Ole Wiley, one in particular has my number and he does not offer a shot lately. Maybe in the hungry time of late winter..........