6 ARC first shots and data.

[backwoods83]

I've never been much of an AR fan, but recently I've been trying to do more, with less. So I've started shooting a lot of small capacity cartridges. Mostly bolt actions, but I find it cheaper to build a quality upper in some cases. 6 years ago, I bought a Stag Varmint in 5.56 match, left it untouched, and it shoots phenomenal with 75gr Hornady bthps over 8208xbr or 80.5gr Berger fullbore targets over H4895. Anyway, I decided to finally build a couple uppers, 6ARC, 224 Valkyrie, 6.5 Grendel, and 6.8 SPC. The first one I finished was the 6ARC. It was a 299$ BCA 16" Grendel side charger to start. The receiver, bolt carrier, hand guard, and barrel nut were all repurposed. I added a Compass Lake 26" 7.5 twist barrel, .936" gas journal, taper to .900" at the muzzle, rifle +2" gas. The barreled is a Criterion blank FWIW. It was ordered with a matching bolt, which was a Monster MK136, and a Superlative Arms adjustable gas block. It has a 19$ Recoil Technologies muzzle break, cheap, but they actually work great. The lower used is the original Stag. I've added a Magpul Gen3 PRS stock, Ergo Falcon grip, KAK buffer weight kit, Tubbs buffer spring, and it came with a RRA 2 stage trigger that I haven't messed with, because I think a 2 lbs pull on an AR is pretty respectable. I use ASC or C Products 5.56, 6.8, and 6.5G 10 round mags, my 5.56 mags have been windowed to allow 2.340" OAL, haven't done the others yet. Anyway, on top is a Crimson Trace 2 series 6-24 resting in a Arken 34mm mount. Cheap UTG bipod, which in my opinion, can't be beat for the 50 buck price tag.

Cases, I didn't want to wait for brass from Hornady, it's likely soft garbage anyway. So I have made cases two different ways. Fireforming Lapua 220 Russian which resulted in a 1.494" case length after forming, starting with a 1.499" case length. Cases were necked to 6mm, trimmed using a WFT 7.62x39 trim chamber, not a perfect fit, but close enough. Charged the cases with a mild load of Imr3031, stuck a 90gr Berger bt .015" in the lands, and lit it with CCI BR4s. Case capacity average of 5 fireformed cases, was 34.96grns of H2O. The second way I made brass, and the cases I used to get velocity data, were Starline 6.5 Grendel cases. I took 50, run them through the AMP to make sure I wouldn't have any issues with splits and I would have good neck tension after sizing. I then run them through a Hornady 6ARC FL die. They came out around 1.519", so I didn't even adjust the WFT for my 6.5 Grendel, and I ran them through, it was set for 1.510 on a 6.5 Grendel case, 6ARC cases came out at 1.478" a little short but not a concern. Capacity average for 5 fired cases was 34.88grns of H2O, given the shorter length, I'd say they are practically identical, and data can probably be used interchangeably, but I haven't made it that far yet.
The numbers.
Starline brass, CCI 450s, Leverevolution, 105gr Berger target vlds, 2.280" OAL, 1.705" CBTO, .010" off the lands.

27.6grns 2578, 2587, 2593, 2607, 2582 average of 2589fps SD of 11.3 group size .913"

28grns 2608, 2612, 2621, 2631 average of 2618fps SD 10.8 group size .864"

28.4grns 2662, 2650, 2658, 2676 average of 2661 SD 10.8 group size .734"

28.8grns 2699, 2696, 2703, 2717 average of 2703 SD 9.3 group size .391" and I believe 28.7-29grns to be the low node.

29.2grns 2762, 2741, 2732, 2740 average of 2743fps SD 12.8 group size back open to .773"

29.6grns 2774, 2781, 2785, 2793 average of 2783 SD 7.9 best SD but group size was .807"

30grns 2836, 2834, 2850, 2825 average of 2836fps SD 10.3 3 shots went .228", the last shot opened it to .739", it didn't feel like a good shot, but this also shouldn't be an OBT.

30.4 I only fired one round because the bolt stuck on me, not sure why, no visible pressure, etc... might be lubrication related, but velocity was 2878fps, and had the same POI as 30grns.
All of this was done on a brand new barrel, new brass, and the gas system turned off.
I plan to test PP2000MR, CFE223, and H4895 as well. Also going to test 92gr Cavity Back MKZs, and 95grn vlds, because I think the high node (2920ish) will be too much pressure with 105s, but I'm going to try it, carefully. I'll continue to add to this, and start other threads on these baby cartridges as I get the time to.

 

[backwoods83]

If you would like to post feedback and or share how far you have stretched a certain small cartridge, feel free.

22 K Hornet 504yrds 40gr Vmax Lil Gun 4 of 5 on a 8" plate.

17 Hornet 20gr Vmax CFE BLK 3 in a row at 504 on an 8" plate.

222R 40gr Nosler Imr4198 3 of 5 on a 8" plate at 504

7.62x39 123gr Nosler CFE BLK 3 of 5 at 504

250 Savage M99 75gr Sierra hp H380 18 of 25 on the 8" plate at 504, while doing a slight fireform from 22-250 brass.

30-30W M99 135gr FTX Imr3031 4 of 10 on the 8" plate at 504.

300 BLK 150gr Speer SP Lil Gun 6 of 10 at 504.

223 30" 7 twist 2 of 5 on a 21" plate at 1435yrds, tried a mile that day, too windy, was all around it.

6BR 115 Dtac PP2000MR 3 of 10 on a 21" plate at 1761yrds, 1 of 10 at 1971yrds.

Will try all of these further as they are slightly refined.

 

[Deleted member 115360]

I am about to bite the bullet and start reloading, but I am a fan of the 6mm arc. I've been smacking coyotes with it since February. It is a dandy. I have been shooting factory ammo, (108 eld-m and 105bthp) both from hornady of course. My 22" ER shaw barrel shoots .5 moa with the 108 eld-m, and closer to one inch with the 105gr. I actually bought an 18" barrel here on this forum, and had about the same accuracy, occasionally shooting one hole groups. I am very interested in hearing how it performs with lighter options. The 55-70gr varmint ammo specifically. I appreciate this information, thank you.

 

[backwoods83]

It's definitely a neat little cartridge, I already have plans for a budget bolt action. Anything related to a PPC (×39) case, or a 6br case, has inherent accuracy from the start. Unfortunately, I like to shoot as far as possible, so likely the lightest I'll test is 87gr vlds. I have a bolt action 6.5 Grendel that doesn't like the heavies, so I can shed some light on what I believe would work best with varmint weight bullets in the 6ARC, 58-75gr bullets, I'd be looking for Power Pro Varmint, H322, H335, W748, AA2230, Benchmark, or Imr8208xbr. I can break 3000fps easily, with a 100gr ELDM in 6.5G with Power Pro Varmint. I'll probably be using the 105gr Cavity Back in it, as it seems impossible to find 107 TMKs.

 

[backwoods83]

More data collected today, for anyone who is interested. I'm still having a bolt unlocking issue that's driving me insane. The rifle has potential though, and the barrel is speeding up slightly. I also made the mistake of drawing 3/8" dots, forgetting that the scope has a half moa center dot, so I'm not making excuses, but the groups could be better.
RL17 data
Reformed Starline 6.5 Grendel brass, trimmed 1.489", CBTO 1.705", .010" jump, 2.280" OAL, 105 Berger vld target, CCI 450s
28.7grns 2603fps avg SD 4.3
29grns 2628fps avg SD 12.5
29.3grns 2675fps avg SD 8.3
29.6grns 2685fps avg SD 10.8
29.9grns 2721fps avg SD 7.6
30.2grns 2741fps avg SD 11.3
Node from 29.7 to 30.3 and a nice full case with minimal powder compression, absolutely no pressure signs.

H4895 data.
26grns 2647fps avg SD 13.6
26.3grns 2672fps avg SD 10.2
26.6grns 2716fps avg SD 8.4
Node appears to be 26.5 to 26.8 grns, good "Stable" powder load with around 90-92% case fill.

Leverevolution data.
28.7grns 2711fps avg SD 4.7
28.8grns 2725fps avg SD 7.9
28.9grns 2728fps avg SD 5.3
Obvious Node here, and 28.9 was the best group of the day.
29.9grns 2832fps avg SD 10
30grns 2837fps avg SD 9.7
Would have been the best group of the day, had I not spanked the last shot to the right.

Target is at 100 yrds and the groups follow the data sequence.

 

[338 dude]

I am about to bite the bullet and start reloading, but I am a fan of the 6mm arc. I've been smacking coyotes with it since February. It is a dandy. I have been shooting factory ammo, (108 eld-m and 105bthp) both from hornady of course. My 22" ER shaw barrel shoots .5 moa with the 108 eld-m, and closer to one inch with the 105gr. I actually bought an 18" barrel here on this forum, and had about the same accuracy, occasionally shooting one hole groups. I am very interested in hearing how it performs with lighter options. The 55-70gr varmint ammo specifically. I appreciate this information, thank you.

When it comes to reloading one of the best ways to learn is to find a mentor near you.(Hint hint)

 

[338 dude]

It's definitely a neat little cartridge, I already have plans for a budget bolt action. Anything related to a PPC (×39) case, or a 6br case, has inherent accuracy from the start. Unfortunately, I like to shoot as far as possible, so likely the lightest I'll test is 87gr vlds. I have a bolt action 6.5 Grendel that doesn't like the heavies, so I can shed some light on what I believe would work best with varmint weight bullets in the 6ARC, 58-75gr bullets, I'd be looking for Power Pro Varmint, H322, H335, W748, AA2230, Benchmark, or Imr8208xbr. I can break 3000fps easily, with a 100gr ELDM in 6.5G with Power Pro Varmint. I'll probably be using the 105gr Cavity Back in it, as it seems impossible to find 107 TMKs.

The 107 tipped match kings are out there if you look in the right places !LOL

 

[backwoods83]

I think I need the 95s, so I can get some speed.

 

[Dmagna]

I haven't had much luck finding a decent powder I like. I have shot just about everything out of my ARC. Star line brass isn't hold up like the Hornady, I have got about 4 reloads before I get a ring just above the head on the case. Hornady brass I have about 7-8 reloads and have no signs of brass damage and it's been pushed hard.

I do like the 90 gr gamechanger, and also the 87 gr absolute hammer. The 108 and 105 are nice but just need to get a powder to work well. I just got some N530 to try, I have already tried N540, n550, varget, lever, 4895,

 

[backwoods83]

I want to try the 92gr Cavity Back, 90gr Berger bt, 95gr VLD, 95gr TMK. There is a higher node around 2910, which would be easy with Leverevolution, CFE223, or PP2000MR, but only in a bolt action, I think it would beat the bolt to death in a AR15, even though lots of people report 2850fps with factory 108 ELD in my barrel length. The lower node at 2690-2740 is very easy with 105s, but the only powder so far that offers a nice full case, is RL17, and it doesn't seem to produce the most spectacular SDs unless it is at full pressure. I think the H4895 will make a good all purpose all weather plinking round for 1100yrds or so, but 2700 just seems kinda slow to me, and the 90-95gr at 200-230fps faster, kills the 105s, all the way out to a mile. Which I don't have enough turret for anyway, but could be done with holdover.

 

[backwoods83]

Data along with the target. Don't use the 6.5 grendel or 7.62x39 loads in an AR. They are about 62k and 56k psi respectfully, obviously not safe for the platform.