6CM to ARC?

[Crews]

Recently switched to a 6 Creedmoor for my main bolt action hunting rifle. Instantly wished I had downsized to 6mm a very long time ago, works great and no recoil. Judy chopped the barrel to 16” (preferred length) and I’m getting 2630 with factory ELD-M. Didn’t expect it to slow down that much but it works just fine for me.

Here’s my question of the day… if I’m not a reloader and happy with 2630, why not 6 ARC in an AR? Seems like I’d get better barrel life.

 

[Dogtown]

6ARC is super popular in AR15s - it's actually designed for that.

 

[rlsmith1]

I own both; 22" Proof CF 6 Creed and 14.7" 6 ARC. The Creed shoots factory 80's at 3145fps and the ARC shoots the same around 2700. If I were you I'd decide how far you are reasonably going to shoot and go from there. If I am very confident my shots will be within 250y, I will grab the ARC but anything further than that and I grab the Creed which is way easier to shoot well (bolt gun) and is just plain faster with dead holds to about 320y.

Check out the 6 CM with the 80 ELD VT and I bet you pick up some speed.

The ARC isn't going to shoot the 108's nearly as fast as the Creed (I'd guess 2450 or so in a 14.5") but that doesn't mean it's useless.

For what it's worth, I've got a shorter barrel 25 CM that I'll be loading 75 VMAX or 85 Ballistic tips for as fast as I can get them going (hoping for 3200 with 75's or 3k with 85's)

 

[TrevK]

18in 6arc AR with factory 108 eldm’s nets me 2580, it’s a good time.

 

[KOL V9]

Not having looked deeply into these specific calibers yet, I'll say this. For me it would come down to this:
6 ARC: If I wanted to run an AR15
6 CM: If I wanted to run a SA bolt gun.

 

[LRRPF52]

Hornady lists 2750fps from a 24” 6mm ARC AR-15

A 20” 6mm ARC AR-15 would get the same speed you’re seeing now from the 16” 6mm CM 108gr ELD-M.

6mm Creedmoor is an inefficient use of case capacity and a long propellant column.

Even the 6x47 is too long. 6 GT is just right for optimum propellant conversion and tight SDs:

To give you an idea of how efficient the little Grendel/ARC case is, compare 6mm ARC with a 105gr to 6mm BRA with 105gr.

This will be bolt gun velocities first, to make it even.

6mm ARC, 105gr, 24” bolt gun:

2800-2850fps

6mm BRA, 105gr, 26” bolt gun:

2900-2925fps

6mm Dasher, 105gr, 26” bolt gun:

2925-2975fps

6mm GT, 109gr ELD-M, 24” bolt gun:

2870fps

6mm CM, 105-108gr, 26” bolt gun:

2980-3100fps

6mm BR, 105gr, 28” bolt gun:

2850-2875fps

The little .441” case diameter shows how well it does compared to the others, and it’s also only doing 50,000-52,000psi. Charge weights are very similar between 6mm ARC and 6mm BR. 6 GT SAAMI MAP is 62,000psi.

You pay a lot of ancillary costs just to get a few fps more velocity, driving 10,000psi higher pressures, using .473” case heads and larger actions, with longer COLs, and you need 2-4” more barrel length to do it with the popular string of PRS 6mm cartridges.

If I was a big 6mm shooter, I would definitely be using the 6mm ARC.

I like the sound and visual splash of heavier, wider bullets hitting the steel, so I shoot 6.5mm.

I used SAAMI, PRS Blog, and Hornady for my sources on velocity and pressures.

 

[Dogtown]

Good Analysis.

I’ve been shooting a 16” 6mm Creed AR10 for some time and really like it, however it’s quickly getting supplanted by my 16” 6ARC AR15. My original goal to to have the same form factor as AR10 .308WIN, but reduced recoil and added effective range, and it sort of delivers on that. It’s much more pleasant to shoot than .308WIN and 95gr VLD TGTs at 2830fps still gets to 1200 yards where I tend to shoot.

Then the 6ARC steps into the fray and now I’ve got a much lighter, smaller frame rifle shooting even more pleasant loads with 103 ELD-X at 2550fps. So slightly heavier and a bit slower, but still very effective against targets inside of 1200 yards.

That has really made me rethink the 6mm AR10, and conclude that it makes more sense to shoot a 6.5mm like you said. The really reason I didn’t at the time was because I already shoot 6.5x47L bolt guns and didn’t want to create any reloading confusion between that and 6.5Creed, but the past year of experience with that AR10 and a couple different 6ARCs has me rethinking things.

 

[MaximusDecimusMeidius]

I will leave the analysis to others that may be smarter and more experienced but here is my chronograph data for a 16" 6 ARC out of an AR with factory hornady 108 ammo

 

[ironhiide]

Good Analysis.

I’ve been shooting a 16” 6mm Creed AR10 for some time and really like it, however it’s quickly getting supplanted by my 16” 6ARC AR15. My original goal to to have the same form factor as AR10 .308WIN, but reduced recoil and added effective range, and it sort of delivers on that. It’s much more pleasant to shoot than .308WIN and 95gr VLD TGTs at 2830fps still gets to 1200 yards where I tend to shoot.

Then the 6ARC steps into the fray and now I’ve got a much lighter, smaller frame rifle shooting even more pleasant loads with 103 ELD-X at 2550fps. So slightly heavier and a bit slower, but still very effective against targets inside of 1200 yards.

That has really made me rethink the 6mm AR10, and conclude that it makes more sense to shoot a 6.5mm like you said. The really reason I didn’t at the time was because I already shoot 6.5x47L bolt guns and didn’t want to create any reloading confusion between that and 6.5Creed, but the past year of experience with that AR10 and a couple different 6ARCs has me rethinking things.

And if you go with a 18" Arc in the Ar15, you get about the same form factor as an AR10 with a 16" barrel due to the 15's smaller stature. 18" 6Arc guns almost touch 2600fps, closing that gap on 6CM a bit. While shooting smoother with a rifle-length gas system at that length too.