Home Brew 6 ARC

[Dino11]

I first heard about this a few months back and was going to build a Grendel. But the 6 ARC caught my interest and I started doing research on it. Although info was limited, and not much was being released about all the testing. I started gathering parts needed to do a build, whether it be a Grendel or an ARC I wanted an AR in a different caliber besides 5.56, and I am not into pistol caliber, 300 BLK just doesn't do much for me. I also kicked around doing a Valkyrie.

About eight months later this came to fruition, thanks to the fine folks at Odin Works. They build some fine barrels and are just great to deal with.

Odin Works 18" 1X7.5 twist, Rifle +2 gas, Odin adj gas block, Odin Atlas compesator, 416 stainless, hand lapped, Odin BCG, Luth AR rifle stock, Vortex Viper HSTII 6X25 50mm scope, and a bunch more good stuff.

Heading to the range this weekend!    

[Lemonaid]

Looking forward to your range report! If you can, record velocity and group sizes. Pics give bonus points!

[Dino11]

Cerakoted Barrett Bronze, hope it shoots as good as it looks.

I will chrono the factory loads and report back, I need the info for when I start loading. I have both 105 and 108 grain. Need to break the barrel in, clean, and zero optic in. Also have to do one for my son , it will be a busy day because I have a new pistol to check out as well.

[6mmARC]

eager to hear about your barrel, I got mine this past weekend but they forgot the XL gas tube, just got tracking number for it today, so it'll be next week sometime to build it...only have 3 boxes of 108s, need to find more but they're all out

[BluntForceTrauma]

Lookin' good!

[VASCAR2]

Cerakoted Barrett Bronze, hope it shoots as good as it looks.

I will chrono the factory loads and report back, I need the info for when I start loading. I have both 105 and 108 grain. Need to break the barrel in, clean, and zero optic in. Also have to do one for my son , it will be a busy day because I have a new pistol to check out as well.

Dino11 I sent you a message on ARF.com didn’t realize you were a member here.  I’m curious about the length of your Odin Works bolt.  When Odin first released their 6.5 Grendel barrels and bolts a couple years ago their bolts measured 2.800” long from the tail to the front of the bolt lugs.  Alexander Arms lengthened the 6.5 Grendel bolt to 2.810” with a bolt face depth of .136”.   Adding .01 to the bolt length keeps the specification the same for firing pins.  

AR-15 5.56/223 bolts have a .125” bolt face depth and overall bolt length of 2.800”.  The specification I’ve found for AR-15 firing pins is 3.279” -.09” tolerance.   With a 2.800” length 6.5 Grendel bolt you don’t want a firing pin longer than 3.269”.

I’m curious if Odin is still using 2.800” length bolt with .136” bolt face depth on their 6 MM ARC BCG. If you get time I’d appreciate it if you could measure your bolt and firing pin lengths. It is good to know specifics of new products on the market since having a firing pin to long can cause pierced primers and a greater chance of a slam fire.

[Dino11]

Range day was kind of a bust today because the long distant range was closed for a varmint shoot that you were only allowed to shoot lead bullets. so we had to go to the 300 yard range. I could not set up the chronograph because this range has a pretty steep slope for about 20' just ahead of the shooting bench. After putting 20 rounds down the barrel I cleaned it and zeroed the scope in @100 yards a little on the low side, only took two shots to zero. Then I moved out to 300 yards and the results were nothing less than spectacular. This barrel is not even broken in yet, and these were 105 grain factory loads. never did shoot any of the 108 grain. I'm very happy with the results, this one is a shooter and a keeper.









These were 7 shot groups and some of the shots went through other shot holes, very thght groups for a 300 yard target. I did not even have to adjust the dope moving out to 300 from a 100 yard zero, thats how flat this thing shoots. But the zero was about 1 MOA low @100 yards, I did this because I knew I would be shooting a distance.

[Biodsl]

Wow. Just wow. Congrats!

[Dino11]

I ended up removing the 20 MOA scope riser, I don't think it is needed inside of 1000 yards. If I can get to the long range I can give it a try without. If the sight picture does not look right because I am at the edge of the glass then I will try it. If thats the case I will get a 20 MOA mount to try and keep the glass as close to the bore center line as possible, not that this is uber important but it does help a little, and it looks better as well.

I barely had to make any adjustment to the scope out of the box setting, the windage was right on, and the elevation only took 6 clicks to set it at the bottom of the 10 ring. two shots and I was printing inside the 10 ring every shot holding at the top of the ring @ 100 yards.

[VASCAR2]

You can probably use your reticle for holdover to get you to 1000 yards. Using Hornady Ballistic calculator for 105 grain BTHP at 2675 FPS I came up with 36.61 MOA needed to get to 1000 yards at sea level. That equates to about 10.6 mils and many scopes have about 70 MOA of adjustment. If your at higher elevation you can probably get by without a canted mount.

I used 2.5” height over bore so your actual inputs will likely be a little different. Still will give you a ball park idea of your 6 ARC capability. With a 6.5 Grendel I like having a 20 MOA mount.

I probably had to much velocity if you have an 18” barrel. I was thinking about velocity out a 20” 6 ARC when I ran the numbers. I just looked at the Hornady load data for the 108 grain ELD and an 18” barrel they are getting about 2575 FPS. The 108 grain ELD-M has a better BC than the 105 BTHP so your elevation where you shoot might make a significant difference if you’ll need a canted mount.

[Pig_Popper]

Nice groups at 300 yards !!!

[Trashy]

Very nice D! Your results corroborate that the 105’s work, that the groups being posted on youtube are a rifle issue not an ammunition issue.

Trashy

[Dino11]

I believe that if you stick to a top tier barrel maker your results will be much better. Proof guarantees a 1/2 MOA, Criterion, Kreiger, Odin Works, are top tier. You will see better results. The further out you shoot, the more amplified barrel inconstancy shows up. 2 MOA @ 100 is 8 MOA @ 400. And if you are referencing some of the Youtube video featuring CMMG rifles, I have heard that they are kinda of in the middle of the road as far as accuracy goes. But their are not many folks making and selling complete rifles right now.

At this point in the game you are better off building a rifle, unless you can get your hands on a Barrett rifle with a Proof barrel, but that rifle will probably set you back about $3500.00. Santan Tactical is another high end rifle, but they are a little spendy as well.

[Lemonaid]

Nice! One of the best results I have seen online. Well done! What did the group measurements end up being?

[Trashy]

I believe that if you stick to a top tier barrel maker your results will be much better. Proof guarantees a 1/2 MOA, Criterion, Kreiger, Odin Works, are top tier. You will see better results. The further out you shoot, the more amplified barrel  inconstancy shows up. 2 MOA @ 100 is 8 MOA @ 400. And if you are referencing some of the Youtube video featuring CMMG rifles, I have heard that they are kinda of in the middle of the road as far as accuracy goes.  But their are not many folks making and selling complete rifles right now.

At this point in the game you are better off building a rifle, unless you can get your hands on a Barrett rifle with a Proof barrel, but that rifle will probably set you back about $3500.00. Santan Tactical is another high end rifle, but they are a little spendy as well.

the barrel in my rifle is from cmmg and I put it together.  

most of the YouTube videos featuring cmmg rifles are loaner weapons that were put out in conjunction with Hornady’s 6 arc release, they have been disassembled and reassembled by every you tuber that has handled them and then some.

the problem within lies in the fact that everybody believes or is under the impression that the rifles are first run weapons and with less than acceptable performance due to the shade tree tinkering, cmmg and more importantly the cartridge itself gets a black eye.  

My barrel is a slim profile and it shoots very well (with the limited range time I have had with factory ammunition), however I would not recommend cmmg to anyone based on the way they treated me as a customer, regardless how I feel about the company the barrel does shoot.  

My point in all this rambling is that I was glad to see your results were along the same line as my limited results, as much as I love both my 6.5 Grendels, it is my belief that this cartridge Fills a hole in the AR platform and I hate to see it lose it’s luster before it gets to shine! My apologies in advance for the rambling.

Trashy

[Chev2500]

I believe that if you stick to a top tier barrel maker your results will be much better. Proof guarantees a 1/2 MOA, Criterion, Kreiger, Odin Works, are top tier. You will see better results. The further out you shoot, the more amplified barrel  inconstancy shows up. 2 MOA @ 100 is 8 MOA @ 400. And if you are referencing some of the Youtube video featuring CMMG rifles, I have heard that they are kinda of in the middle of the road as far as accuracy goes.  But their are not many folks making and selling complete rifles right now.

At this point in the game you are better off building a rifle, unless you can get your hands on a Barrett rifle with a Proof barrel, but that rifle will probably set you back about $3500.00. Santan Tactical is another high end rifle, but they are a little spendy as well.

2 M.O.A. at 100 will be 2 M.O.A at 400

[Thelaststraw]

Please correct me if I'm wrong as I'm new to rifles and precision shooting all together. Practical pistol background so A zone IPSC is precision...lol.

Yes, 2 MOA is 2 MOA going by units of measure (ie= inches). But if a barrel, or shooter has 2 MOA variance at zero range. Could they be saying that that deviation from POA=POI is amplified at distance? I'm asking for me mainly as I'm learning by reading mostly currently. I'm very new to this and the itch needs scratching so I'm trying to learn as much as possible. Thank you.

[grayfox]

MOA is a relative measurement, so technically 2 MOA "rifle" at 50 yd=2 MOA at 100 yd=2 MOA at 1000 yd. The actual spread in inches differs, 1", 2", 20" respectively.
But practically speaking, some of that MOA for most shooters, is shooter error; thus, your group might tighten up at longer distances... or might not. So we need to talk about the MOA of the entire system, not just the rifle. Load, rifle, scope, shooter, shooting rest, wind etc.
Precision shooters and excellent marksmen can talk about rifle accuracy b/c they can rule out most shooter issues.

The other thing in this is that, on a given day you might shoot 1 MOA, then 1.5, then 2.5 with the same rifle, same loads. So you need to have several groups spread over several days to get a good idea how good the rifle is.

Finally, some bullets are said to need some yardage before they "settle down" -- could look like 2 MOA at 100 but might be 1 MOA at 300. I've never seen that nor have I seen how someone accurately measures it, but I guess it's possible.

[Thelaststraw]

Thank you, that makes perfect sense. I neglected the fact that MOA (in units of linear measurement) increases from with distance, hence the ANGLE part of the acronym. I have a lot to learn, or at least become second nature, to not need things I already know reiterated to me. Then I won't need to ask silly questions. 

[grayfox]

No such thing as a silly question. If you’re wondering then someone else is too.