6mm ARC

[PrecisionFirearms]

We are taking orders for these in our own inhouse Button Rifled 5R and Cut Rifled 5R, Criterion, Bartlien 5R Cut Rifled, and Krieger Cut Rifled. First ones should be shipping in 6 weeks. In Samurai Button Rifled, PF Button Rifled, Criterion, and Bartlien. Krieger and our own inhouse Cut will be longer.

Mark Hostetter
Precision Machine (Firearms)

[Silverjay]

Got out today with the Ballistic Advantage barrel from Brownells in 20”. I dropped it into a Larue built 6.5 Grendel and put a new Monster bolt in. Low profile standard gas block and no break. Shot four groups getting it zeroed with Hornady Black all of which were about 1”. Kicking myself, I left the Magneto speed on the bench.

Went to the steel range to stretch it out. I plugged 2750 into TRASOL and found at 420, 566, and 720 that impacts were a bit high. Trued it to 2720 and it was ringing steel at 840, 950, and 1090. All of the steel is roughly full sized IPSC. Wind was 16 mph from 120 degrees, it handled the wind well. Recoil was very nice and spotting was easy without a brake.

Ran 50 rounds through it and the groups seemed to tighten up some. Last 5 rounds were at 420 and well under 1 MOA. I didn’t bother driving out to measure. I will take the chrono later this week and confirm.

[cb4017]

Well darn, right when I was thinking of downsizing the contents of my safe.

[Trashy]

DO NOT believe that crap from CMMG that they have barrels in stock! I ordered their stainless 20" 6mm ARC barrel on June 4th because they showed in stock. They let me put it into thier cart, checkout and took my money. EIGHT days later on June 12th they sent me an email stating they added a note to my order which stated "Order "on hold" and on pre order for 2-4 weeks. 06/12/20 ZH".

IMO that is false advertising, everybody else listed arc barrels as pre order on thier websites, NOT CMMG!!! They have my money so now I am committed, hope they enjoy my $239.95 it will be the last that they get from me.

[Gtscotty]

We are taking orders for these in our own inhouse Button Rifled 5R and Cut Rifled 5R, Criterion, Bartlien 5R Cut Rifled, and Krieger Cut Rifled. First ones should be shipping in 6 weeks. In Samurai Button Rifled, PF Button Rifled, Criterion, and Bartlien. Krieger and our own inhouse Cut will be longer.

Mark Hostetter
Precision Machine (Firearms)

Is the 6mm ARC being added as an option on your web order form, or will it be a call in type of proposition? I went to look on your website yesterday and didn't see ARC as an ordering option.

[grayfox]

Any chance some of you guys with Quickload might work out some approximate load ideas for this 6Arc? I'm thinking possible powders like RL-15, H335, Varget, H4895 or I4895, TAC, maybe CFE223, AA2520 (?), 8208xbr(?)... Not sure of the exact case capacity but seems something around 30 grs.
105 Hdy BTHP, 107 Sierra, 103 Eldx, 108 Eldm, Sie 90 TGK.... take your pick.
Use 20 or 24" AR-barrel take your pick.
These estimates could give us something to ponder while we salivate over the barrels... which are in short supply right now!

[SDguy]

Another propellantI Would hope to see data on will be LVR W 100 gr projectiles & up.

[mopar_4life]

I bet 6ARC won’t be in quickload for a while.

[Gtscotty]

I bet 6ARC won’t be in quickload for a while.

My plan was to get an average h2o case capacity from a few fired cases, and modify the 6mm AR settings in QL to match. Should be able to get a decent idea and then true with velocity.

[stubshaft]

DO NOT believe that crap from CMMG that they have barrels in stock! I ordered their stainless 20" 6mm ARC barrel on June 4th because they showed in stock. They let me put it into thier cart, checkout and took my money. EIGHT days later on June 12th they sent me an email stating they added a note to my order which stated "Order "on hold" and on pre order for 2-4 weeks. 06/12/20 ZH".

IMO that is false advertising, everybody else listed arc barrels as pre order on thier websites, NOT CMMG!!! They have my money so now I am committed, hope they enjoy my $239.95 it will be the last that they get from me.

I just hate when companies pull this garbage. I won't order from them at all.

[Silverjay]

6mm AR is in Quickload and is very close. The 6mm AR shows 1.5 grains H2O more than what I measured on the Hornady ARC cases. Thoughts on trying the volume and using that?

[grayfox]

I thought the delta was more like 0.4-0.5 grs. I don’t have any measurements however.

[Silverjay]

Quickload defaults to 36.0 for the 6mm AR case volume. I measured 5 fired cases and they were all between 34.3-34.8. At 34.5 grains H2O Quickload was within 20 FPS with Hodgdon LVR. There was a velocity node around 52k that had 108’s doing 2,590 FPS.

[grayfox]

I just did a quick look-back on some earlier QL threads on here, on the Grendel cartridge. One common theme was the theory that for a shorter case, like the Grrr, primer ignition can bump out the bullet, both starting it out velocity wise and enlarging the effective case volume for the powder burn. Both of these seem to impact MV performance but QL was variously characterized as over- and under-predictive. It was also commonly said that the MV curve's slope matched mfr and reality curves... only offset by a more or less delta-velocity figure -- Klem and JAS in particular worked this out in some 2019 posts. Finally, some were able to match up QL predictions to their real-world MV's by upping the case volume from ~35 or ~36 (depending on the commenter) to ~38 grs.
If these things are put together into a common theory then a bump of the bullet would increase the effective case volume, and the movement and geometry being changed from the QL model, MV might suffer/predictions-off, but be some relatively constant delta-value with similar slopes.

I write this to pose that perhaps the same things could be expected in our new, short-cased 6Arc, esp where lighter bullets of ~100 gr (vs the Grendel 123 gr) are concerned. Relatively slower powders burning for the 6Arc will also have some kind of impact.

It will be interesting to see how real MV's, and real pressure, come out in comparison to QL.

[phishfood]

Some load workup already going on with this cartridge.

https://www.youtube.com/watch?v=i1o_NPfxTUc

[Silverjay]

Ran 20 rounds over the chrono this morning checking SD and accuracy in the velocity node I found. Velocity settled at 2580, SD was 9, and produced four groups of five rounds each just over 1/2” at 100. I think I am done until the Lilja barrel gets here.

I played with some other powders in Quickload and none of them I tried produced a better velocity/pressure relationship. I didn’t have to increase the case volume from actual to get a good velocity prediction.

[grayfox]

I have some factory 105's inbound, but am waiting on a barrel.
The main ~100 load I'll be interested is the 103 Eldx.
After that then maybe the 90 Tgk.
My bullet range I think will be 90-105-ish.

[Mitdr774]

I have a partial box of 103 ELD-X that is begging for a gun to shoot them through. My .243 does just fine with several 100gr bullets, but the 103 was just too long and resulted in something like a 6" pattern at 100 yards. Holes were not circular.

[BluntForceTrauma]

I have some factory 105's inbound, but am waiting on a barrel. The main ~100 load I'll be interested is the 103 Eldx. After that then maybe the 90 Tgk. My bullet range I think will be 90-105-ish.

I'm starting to build up 6mm components. Got some 6mm 90gr Tipped GameKing (TGK).

Gonna use the same 90–105 weight range you mentioned. Well, I'll probably try Berger's 109 if it looks promising in ballistics charts.

Can't decide between Berger 105 or Nosler RDF 105, though. Probably go with Berger since it's such a known standard, for comparison's sake.

For loading data, I'm just gonna take the body of 6mm Grendel/6mmAR data and reduce by, oh, half grain.

[mopar_4life]

I'm starting to build up 6mm components. Got some 6mm 90gr Tipped GameKing (TGK).

Gonna use the same 90–105 weight range you mentioned. Well, I'll probably try Berger's 109 if it looks promising in ballistics charts.

Can't decide between Berger 105 or Nosler RDF 105, though. Probably go with Berger since it's such a known standard, for comparison's sake.

For loading data, I'm just gonna take the body of 6mm Grendel/6mmAR data and reduce by, oh, half grain.

I would also check out the Vapor Trail Automated 103 bullets.