Righto curiosity got the better of me last night and I slapped 5 cartridges together to do a quick test on the way home from work.

Obviously 6 PPC data was a safe starting point,  I did have some Re10x on hand  which would rocket along but the safe option was 8208.   I've been loading a compressed loads of 8208 in my Grendel for years so I had little hesitation with 32gr and giving it a light crush.

Hornady 6mm ARC brass, 1.49in, Rem 7.5,  8208, Nosler 55gr BT,  COAL  2.130

Charge        Velocity

32.0            3494  3493  3469  3493  3494

5 shot group went 0.7 MOA which I wasnt expecting.   This is a start load but Id be surprised if I could fit another 2 grains of 8208 in the case,   I reckon with the right powder 3700fps would be achievable.......

Yes they have them!

https://www.huntingtons.com/store/produc...751&page=1

Just ordered a set, will pay over the phone later today.

Found some 6mm ARC ammo at ammo seek... Kinda pricey but it's there. Don't know how long it will be in stock...

https://www.laxammo.com/hornady-6-mm-arc...604-detail

https://www.freedommunitions.com/hornady...match.html

https://www.freedommunitions.com/hornady...match.html

Gents,

Im building a 6mm ARC AR15. And I am really excited about the prospects of having it all finished and running smoothly. I was at the range today shooting the first few rounds throo the barrel to break it in before sending it off for nitriding.  But ... after sending a round down range the empty case sticks n the chamber. with a bit of extra force I can extract the casing. This happened 12 out of 12 times.  On examination of the casings all of them seem to have two “scratches” on the neck parallel to the long axis of the case. Any input would be appreciated.

Al

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Yesterday was my first reloading session for my Howa Mini Arc. I used some discontinued Nosler 105gr Custom comps with Leverevolution to get a good baseline as to whether Hornadys published data was credible.  I also put a fresh battery in the magnetospeed.

Thought it would be an interesting exercise to load up some ARC brass and test against some formed from Grendel brass.

I used Hornady reloading data as a guide and my speeds matched up well considering my barrels 22 inches

Hornady 6mm ARC brass, 1.49in, Rem 7.5, LVR

Charge       Velocity

29.7           2727  2750  2758  2727  2735
30.0           2776  2769  2776  2792  2771
30.3           2794  2795  2805  2813  2793
30.6           2817  2801  2811  2826  2807

Hornady 6.5 Grendel brass, 1.49, Rem 7.5, LVR

30.0           2810  2805  2817  2792  2826       6.5G brass produced an ave speed 33fps faster than ARC brass
30.6           2802  2825  2811  2847  2847

No pressure signs observed at all,  primers and cases look good.  

Best load was the ARC brass at 30.3gr,  groups size was 0.5moa

And I managed to find a little brass 

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I have found that long protruding bullets are vulnerable to several kinds of accuracy issues.  It is well know that gas gun chambering eats the tips on soft lead bullets and can cause concentricity imbalance.  I have tested it with 6mm Creedmoors using LR308 frames.  The result at 100 yards with an standard hunting SP bullet was 7+ MOA, BTHP less than 1 MOA.  Well the same thing applies with 6mm ARC beyond bullet tip problems.  The gas gun barrel extension can also be a cause of flyers in a good group.  I have two 20" barrels, Faxon and CMMG.  Faxon has standard untouched M4 barrel extension while the CMMG is modified.  Feed ramp contact during chambering can screw up seating alignment just as easily as poor hand loading.
Attached images show ARs and barrel extension scaring.  Anybody else found this kind of issue?        

And new to the 6mm ARC, and fairly new to rifle handloading. 

I've been a plinker, and hand gunner, occasional hunter, and general firearm enthusiast most of my life, since I got my first .22 bolt gun at 8. Been reloading pistol, and very NON precision rifle plinkers off and on since around the same age, starting with grandpa in his garage (also where he kept the whiskey), so he'd spend alot of time out there. 

I've been dabbling in rifle hand loading for a few years now, and playing around in the 6.5 Grendel world. My infatuation with 6mm goes back to deer hunting with 6mm Rem. I was always sure my 30.06 hunting buddys were secretly jealous of my choice. I haven't hunted with the Grendel, though that was the original plan, build an upper I could slap on an AR lower, and go hunting! Then I started to enjoy punching paper, and hand loading once I had a feel of what the 6.5G could do on an AR platform. 
 
So I guess it was just a matter of time.... Still waiting on my Uintah 6mm ARC upper that I ordered just a week ago. It will share a rifle case and a lower receiver with my 20" Grendel upper.

Like I said, I'm brand new, haven't received my upper yet, but I already bought a set of Hornady dies, and ordered some bullets. No brass that I can find, though I may resize some Grendel brass just to get me in the game. Like alot of folks, I'm powder challenged at the moment too. 

Happy to have found the group, and to be part of the community here. 

Chris

I've enjoyed the shooting sports pretty much my entire life and been reloading since the 80's. Started out loading bolt guns and pistols and got into the AR game a few years ago. My 1st build was a 5.56 and then 300 blackout after that. It's been on my bucket list to build a precision to me rifle on the AR platform and the 6 ARC just seemed to be the ticket. On Feb 1st I ordered an X-Caliber bull barrel and now I have the next 2-3 months to acquire all the parts to complete my build. Slowly but surely I'm getting there. Also working on building a reloading component stash between now and the day the build is done. Of course these are trying times to get components and that's why I'm here. Learn all I can about successful powders, bullets, primers, brass, etc. I've been reading through the posts for that last several days and I'm sure I'll be posting some questions and hopefully adding value to the forum once I start doing some load development.

Evening all, thought I'd start a build thread on my first 6mm in 25 years.

This is my 3rd Howa mini action I like em.  Some will grumble about the Mag release and a lack of floor plate but I like the dynamics of the short action slick action which feeds the Grendel case like butter.

The 20 inch Grendel HB came off without drama and my gunsmith did an awesome job with a profile similar to the one that came off, albeit with an 2 extra inches and smidge more around the knox.  Overall weight shouldn't be much more than before.

Arc Ballistics UK made the reamer and a Bartlein 1:8 twist barrel was used.

I have some Hornady Black 105gr HPBT ammo for run in and I've already converted some 6.5 Grendel Hornady cases using the Hornady 2 die set.

Off to the range shortly for run in...

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Hi.  New to the forum and new to the AR-15, though not new to the M-16.  I've been shooting as long as I can remember, reloading for a long time, but not as seriously as I ought.  Now that I'm retired, I have time to do all those things more seriously.  I've been sitting on a stripped lower for quite a while and thinking about what to do with it.  I got excited about the Valkyrie but waited long enough to see that it wasn't the end of all things.  Then the 6mm ARC came along and I jumped.  I've built a 6mm on a conventional lower with an Aero Precision upper and BA barrel.  Happy to be here to follow the progress of others experience with this new cartridge and learn from all the wisdom you have to share.