6mm ARC Thread

Mountain

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There was some discussion of this in the Sig Next Generation Squad Weapon, but I did not see an individual thread. I'm going to take a drink of this new Kool Aid flavor. There are a number of articles out there, but this one is a relatively quick read with some comparative 500 yard+ performance vs. the .223 and .308.

Everything You Need To Know About The 6mm ARC

Vs. 308, it has better long range ballistics, less than half the recoil, and is a 30% lighter rifle platform than a 308 AR. What's not to like? LOL I do have to hold my nose a bit as this caliber is a Hornady development and I think Steve Hornady is a jackass.

I plan to borrow the lower from one of my AR15 match rifles and will build an upper with the goal of having a long distance range toy. In the near future I'd like to take some courses at Ridgeline and after trying some 22NRL matches may step up to centerfire PRS matches. I already built an AR 6.5CM and Mrs. Mountain has a nice 308 Aero M5, so those calibers are covered. I thought about a 6CM rebarrel of my 6.5, but 6CM tends to burn through barrels more quickly and is a little hotter than I really need. I can always do that later for relatively short money but I'll probably just stick with the 6.5.

One of the logical digs against the 6 ARC is its lower velocity out of a gas gun. SAAMI specs are 2700 fps for a 108 grain projectile at 52,000 psi. I assume that's a bolt action 24" barrel. Hornady load data lists 52,000 psi as the limit for gas guns yet specs a limit of 62,000 psi for bolt guns. Like the 6.5CM AR I built, I'll use a high pressure JP bolt headspaced to my new barrel which will facilitate slightly hotter loads. Another point of attraction for me is that some of the best heavy projectile 6 ARC loads use Varget and 2520, of which both I use and keep stock in bulk. I'll use one of the better match barrel makers for a 24" (maybe a 22"?) barrel and run a rifle +2 gas system. Might take a couple months before I have my new barrel, but as I have done with prior 'builds' will post targets good or bad along the way.

I realize there are better performance options, but as far as I have seen thus far those options are all in the AR-308 platform. For the cost of a new barrel + bolt, new mags, and not much else we'll see how it goes...

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Placed the order today for a (high end match barrel producer) barrel made via a 1:7.5 Bartlein blank. Heavy varmint profile with a .875" diameter at the gas block. I went with 24" and Rifle +2 gas length. I'll have them headspace a new JP Enhanced bolt. Below is a shorter version of the barrel.

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12 week lead time from (barrel producer). They are busy because they deserve to be busy, IMHO. Very happy with their prior work. First Bartlein barrel I have ordered, others being Kriegers and Criterions. I'm curious what velocities I can generate with the 24" barrel and +2 gas system. I'll lap the upper receiver mating surface before installing the barrel. Before attempting to develop loads I'll benchmark the accuracy with factory Steve-the-Jackass-Hornady match rounds. [laugh]
 
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It’s a good cartridge, and has some benefits in an AR vs. 5.56. But when you cut that barrel down to under 20” you’re not getting all that long range performance that people rave about vs. the 308. Cut down to 20” or less in a gas gun and you’re looking at similar but slightly better long range trajectory to a 6.5 Grendel. Only you can’t find brass for it. Hornady has been the only gig in town and all the brass they make is going to factory ammo for it. Now, you’re good to go if you can find factory ammo for it. Or, if you form the brass from its parent cartridge or even 6.5 Grendel.

Ita a good cartridge. It may even be the best long range cartridge for the AR platform (by a relatively small margin in my opinion). But to me it’s not worth jumping through hoops to figure out how to get some of it to shoot, when it’s performance is vastly overstated.

And If you put it in a 24” bolt gun, you get great results when compared to a 16” gas gun. But not compared to so many other 24” bolt guns. Not even compared to a .243. It’s a neat little cartridge, but I think it’s a little over-hyped.
 
It’s a good cartridge, and has some benefits in an AR vs. 5.56. But when you cut that barrel down to under 20” you’re not getting all that long range performance that people rave about vs. the 308. Cut down to 20” or less in a gas gun and you’re looking at similar but slightly better long range trajectory to a 6.5 Grendel. Only you can’t find brass for it. Hornady has been the only gig in town and all the brass they make is going to factory ammo for it. Now, you’re good to go if you can find factory ammo for it. Or, if you form the brass from its parent cartridge or even 6.5 Grendel.

Ita a good cartridge. It may even be the best long range cartridge for the AR platform (by a relatively small margin in my opinion). But to me it’s not worth jumping through hoops to figure out how to get some of it to shoot, when it’s performance is vastly overstated.

And If you put it in a 24” bolt gun, you get great results when compared to a 16” gas gun. But not compared to so many other 24” bolt guns. Not even compared to a .243. It’s a neat little cartridge, but I think it’s a little over-hyped.
It was overhyped.

That said, it is still competent at long range compared to 308, even in sub-20” barrels. Keeping in mind that 6 ARC was originally designed for 18” barrels.

Using Strelok and some velocity data I found on Snipershide, it seems to shoot pretty comparably to 308 using like bullets. This is at 1000 yards with 10 mph full value wind:
CalBulletBarrelMuzzle_Velocity1k_Velocity1k_Energy1k_WindDrift
6 Arc108 ELDM18”2540 fps1161 fps323 ft-lb99.7”
308168 ELDM18”2523 fps1123 fps470 ft-lb104.8”

Not bad for a smaller, lighter, less recoiling package. Some 18” barrels are even shooting the factory 108gr ELD-M just under 2600 fps.

But yeah, there are other better options if you want a longer bolt gun for long range performance. Like 6 GT.

I don’t have a dog in the fight, but disclaimer I probably will give it a try if Criterion comes out with a Core or Hybrid series barrel for it.
 
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I have looked at 6 ARC and 6.5 Grendel. There are many similarities between them. Of course, a skinnier and longer bullet will fly faster. That said, I would advise looking at the whole picture. Ask yourself these questions:
  • How much does the ammo cost? A quick search on Ammoseek shows $1.65/rd for 6ARC and $0.74/rd for 6.5 Grendel. At twice the cost, you have to think if 6ARC will be your showcase gun rather than your competition/daily use gun.
  • Can you afford to train with this caliber? A typical PRS match uses about 300 rounds. A typical Precision Rifle course uses 500 rounds, and a typical battle rifle training uses 1000rds. Can you afford a $1600 bill for the ammo for a weekend of training and fun?
  • Can you buy a rifle with this caliber? Virtually every wholesale AR shop sells 6.5 Grendel rifles, uppers, and barrels. The number of stores that offer 6ARC bolt guns is virtually zero, and 6ARC gas guns selling stores are few, with the majority being out of stock.
  • Can I reload for this caliber? While dies and bullets are fairly easy to come by, 6ARC brass cases are unobtanium. The only way to get them is by buying ammo and shooting it.

The point I'm trying to make is, well, get a Grendel, or don't bother at all.
 
I have looked at 6 ARC and 6.5 Grendel. There are many similarities between them. Of course, a skinnier and longer bullet will fly faster. That said, I would advise looking at the whole picture. Ask yourself these questions:
  • How much does the ammo cost? A quick search on Ammoseek shows $1.65/rd for 6ARC and $0.74/rd for 6.5 Grendel. At twice the cost, you have to think if 6ARC will be your showcase gun rather than your competition/daily use gun.
  • Can you afford to train with this caliber? A typical PRS match uses about 300 rounds. A typical Precision Rifle course uses 500 rounds, and a typical battle rifle training uses 1000rds. Can you afford a $1600 bill for the ammo for a weekend of training and fun?
  • Can you buy a rifle with this caliber? Virtually every wholesale AR shop sells 6.5 Grendel rifles, uppers, and barrels. The number of stores that offer 6ARC bolt guns is virtually zero, and 6ARC gas guns selling stores are few, with the majority being out of stock.
  • Can I reload for this caliber? While dies and bullets are fairly easy to come by, 6ARC brass cases are unobtanium. The only way to get them is by buying ammo and shooting it.

The point I'm trying to make is, well, get a Grendel, or don't bother at all.
All fair. 6.5 Grendel is a neat cartridge.

But the heavier bullets just didn’t appeal to me. Even with 300blk, I run 110s.

And out to just 200 yards, with equal barrel lengths and both using ELDM bullets, the 6 ARC already beats 6.5 Grendel in energy and wind resistance. If one already has a Grendel, yeah the juice probably isn’t worth the squeeze. But as someone who doesn’t have a Grendel and is now interested with the lighter bullets, I’m just going straight to the 6 if I go for one of them. New cartridges will always be pricier. And for those prices you compared, those are plinking ammo prices for the Grendel. They cost virtually the same for quality ammo you’d use for a PRS match or SPR/scoped carbine course.

However, 6 ARC may be short lived. RUMINT says the military element testing it had bolt durability problems like many in the 6.5 Grendel community have known. And may not continue using it. Looks like 6 ARC is going to need to survive on its long range competition credentials if it wants to survive.
 
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Like all new shiny things, yeah- it gets overhyped.

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@PappyM3 's Strelok data shows one of the big advantages of this cartridge. IMHO it appears to be the best long range games caliber for gas guns. Even in a shorter AR barrel, at a minimum it will produce 308 level long distance performance (excepting energy) in a much lighter package. Add weight accordingly to balance out your rifle and it's still a much more svelte package than the AR-308 (says the man with a 13 lb AR service rifle). Once you push the velocity a bit, 6 ARC outperforms 308 by a decent margin. Now consider the much lower recoil which will make spotting your hits much easier.

Yes, I'd probably go a different direction for a bolt gun but one of the more experienced guys on Snipers Hide actually prefers 6 ARC in a bolt gun. Why? 4,000 to 5,000 rounds of match level accuracy vs. about half as many for the hotter 6mm cartridges unless they are down-loaded to the lower end of their velocity range. He also states 2700-2800fps range is the best for the 6mm's to stay supersonic to 1200 in most cases, as well as go slow enough to watch all impacts. I'll be running a 24"barrel so let's see if I can get 2700 fps without stressing the brass.

Yes, the ammo prices currently suck (thus my Steve Hornady Jackass comments) and brass is unobtainium. But guess what- help is on the way. Peterson Brass will be releasing 6 ARC any day now and Starline plans to release it sometime this year. I can always re-form 6.5 Grendel brass if I need to.

@40 Creedmoor fan - get a Grendel or don't bother at all? 🤨 That $0.74/rd price is for steel cased mag dump quality ammo. I built an AK to fulfill that role at a much lower cost per round than 6.5 Grendel. Assuming moderate brass life I should be able to reload match quality 6 ARC for ~$0.80 per round which will be cheaper than my 308 and 30-06 match reloads due to the lower powder capacity.

@PappyM3 , my barrel source is making 6 ARC barrels from Criterion blanks. Don't know if/when Criterion will have their own. Ballistic Advantage has several options for 6 ARC barrels. They no longer ship to MA since merging with Aero but I'm sure there are work-arounds if you are in MA.
 
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@PappyM3 , Compass Lake is making 6 ARC barrels from Criterion blanks. Don't know if/when Criterion will have their own. Ballistic Advantage has several options for 6 ARC barrels. They no longer ship to MA since merging with Aero but I'm sure there are work-arounds if you are in MA.
Thanks. Unfortunately I’m specifically hoping for Criterion to release 6 ARC in their lapped chrome lined barrels. I’m okay with 0.75-1.25 MOA and much longer barrel life rather than 0.5-0.75 from stainless heavy match barrel. For this purpose anyway (fun at matches and maybe hunting).

But I look forward to updates on your build.
 
I should have been more clear. I do not advocate for 6.5 Grendel. Rather, I'm advocating against 6 ARC adventures.

If you want precision in 6mm, 6BRX, 6 Dasher, of 6CM are far easier to find support for in the community.
If you want a AR-15 size gas gun, heavy 223 bullets do pretty well still.

6ARC is a nice cartridge but the only reason to go with it is if you have a 6.5 Grendel gas gun. You should have plenty of brass then.

@Mountain, price is price. Steel ammo will shoot just fine for practice, or classes. The choice is yours. Meanwhile, there is no such choice for 6ARC.

Personally, I think 6ARC was an attempt by Hornady to reuse a custom cartridge they tried to sell to the military. The military trials concluded, and 6ARC failed. Hornady still had the tooling and development notes. They saw how popular 6mm is in the precision community and decided to ride 6mm gravy train. COVID kinda killed it though.

I also noticed that Hornady is following Alexander Arms' path and not opening up ammo production to anyone else. This approach killed 6.5 Grendel, and I fear 6ARC will die the same death. 6.5 Grendel is a very niche cartridge, to say the least. 6CM,

The Grendel user community was shrinking day by day until 6ARC came along and people felt they could become the "cool" kids again. Everyone started switching barrels to 6ARC and walking around like they own the lunch hall.
 
I should have been more clear. I do not advocate for 6.5 Grendel. Rather, I'm advocating against 6 ARC adventures.

If you want precision in 6mm, 6BRX, 6 Dasher, of 6CM are far easier to find support for in the community.
If you want a AR-15 size gas gun, heavy 223 bullets do pretty well still.

6ARC is a nice cartridge but the only reason to go with it is if you have a 6.5 Grendel gas gun. You should have plenty of brass then.

@Mountain, price is price. Steel ammo will shoot just fine for practice, or classes. The choice is yours. Meanwhile, there is no such choice for 6ARC.

Personally, I think 6ARC was an attempt by Hornady to reuse a custom cartridge they tried to sell to the military. The military trials concluded, and 6ARC failed. Hornady still had the tooling and development notes. They saw how popular 6mm is in the precision community and decided to ride 6mm gravy train. COVID kinda killed it though.

I also noticed that Hornady is following Alexander Arms' path and not opening up ammo production to anyone else. This approach killed 6.5 Grendel, and I fear 6ARC will die the same death. 6.5 Grendel is a very niche cartridge, to say the least. 6CM,

The Grendel user community was shrinking day by day until 6ARC came along and people felt they could become the "cool" kids again. Everyone started switching barrels to 6ARC and walking around like they own the lunch hall.
All great comments.

Keep in mind this is all under the context of a standard AR sized gas gun. I'd probably go 6 GT or the like in a bolt gun and 6 CM if I wanted to re-barrel my 6.5 gas gun.

For sure, heavy .223 would be a much more practical option but in my opinion (not worth much) take your pick of 80's and they all get blow around a bit at 600 yards. I've shot both the .223 80's in service rifle competition as well as Lapua 167's and 175 TMK's in Vintage Sniper at the Camp Ethan Allen Range #4 600 yard line. That valley is like a blender, often with the wind flags pointing opposite directions. A 20 mph 90 degree wind moves 175 TMK's about 50" while the 80 .223's will move ~70". Not really apples to apples as my service rifle has a free-floated heavy Krieger barrel done by CLE and my Vintage Sniper rig just a basic stock Criterion barrel. The sniper is a WW2 1903 Springfield built as a USMC sniper clone, yet I tend to score better with that old hardware in crap conditions. Fewer shots get blown out of the 10-ring. Shot a 98-2X in the 600 yd stage during stormy weather last September, shooting buddy and I got silver.

LOL so basically the 6 ARC is a crutch for my mediocre wind reading skills. Also my 6.5 CM gas gun has no brake and it's a bit hard to keep the impacts in view. Totally admit I'm being a bit of a guinea pig here. Once the barrel comes in and I mount it up, I'll be one or the other of these:

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It was overhyped.

That said, it is still competent at long range compared to 308, even in sub-20” barrels. Keeping in mind that 6 ARC was originally designed for 18” barrels.

Using Strelok and some velocity data I found on Snipershide, it seems to shoot pretty comparably to 308 using like bullets. This is at 1000 yards with 10 mph full value wind:
CalBulletBarrelMuzzle_Velocity1k_Velocity1k_Energy1k_WindDrift
6 Arc108 ELDM18”2540 fps1161 fps323 ft-lb99.7”
308168 ELDM18”2523 fps1123 fps470 ft-lb104.8”

Not bad for a smaller, lighter, less recoiling package. Some 18” barrels are even shooting the factory 108gr ELD-M just under 2600 fps.

But yeah, there are other better options if you want a longer bolt gun for long range performance. Like 6 GT.

I don’t have a dog in the fight, but disclaimer I probably will give it a try if Criterion comes out with a Core or Hybrid series barrel for it.

Those are good numbers, you are right. I haven't seen 2600 FPS from an 18", but I've seen low 2600s from a 22. I think it is unusual for an 18 to shoot that fast, but I don't doubt it. I will say that the powder in the factory 108 ELD-M loads that I've seen seems to generate more velocity than what they've published for the top velocity producing powders (CFE223 and Lever). However, it does seem that with most barrels, the trade off for the extra velocity of the factory rounds seems to be accuracy. I think the cartridge may be particularly susceptible to OAL, or it may be that most factory chambers are too deep. The problem is, you can only get so much OAL out of the cartridge and still fit it into a magazine. If I were to buy a 6 ARC barrel, I would have it custom built with the chamber set back a bit.

If more crash test dummies get some real world data on the cartridge, and maybe some more powder choices become available that really can push the 108s a good way into the 2600s with their most accurate load, I'll buy a barrel. But I also need the brass to become available.

I like the 6 ARC, for a lot of use cases, as a choice of a 20" rifle on the AR15 platform vs. a 308 on an AR10 platform. The info you provided speaks for itself. I think maybe where I'm not so hot about it is probably vs. the 6.5 grendel. I don't think it is a better choice at the moment. But, thats maybe not what this thread is about and I don't want to derail it in that direction. That said, if someone didn't have either platform and brass and factory ammo was as available for both, then I would say maybe go with the 6 ARC if you're looking to shoot 600+ yards.

Another thought though. Why are we comparing it to the 308 AR10? Why not the .243? The .243 Destroys it. The .243 needs the larger form factor like the 308 for a platform. I think it makes more sense to compare the 6ARC to the .243 on the AR10. I think the reason you hear it compared to the 308 is because of marketing only.
 


Another thought though. Why are we comparing it to the 308 AR10? Why not the .243? The .243 Destroys it. The .243 needs the larger form factor like the 308 for a platform. I think it makes more sense to compare the 6ARC to the .243 on the AR10. I think the reason you hear it compared to the 308 is because of marketing only.
I believe the original intent of the cartridge was to replace 7.62x51 gas guns in certain USSOCOM units for particular CONOPS. They wanted something lighter, using the normal M4/M16 lower, and with faster follow up shots than 7.62x51, but without sacrificing the external ballistics of 308. Hence the comparison.

The 243 is a great round, but doesn’t let you load the longer high BC bullets. Same reason why USSOCOM went with 6.5 CM over 260. The 260 offered more powder capacity, but they wanted to future proof a bit for long bullet designs.
 
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Have you sourced brass yet?
i would re-iterate this question as it was where i kinda stopped myself while looking at what to do with the last available ar15 lower.
it`s neither cheap nor widely available, that kinda makes it suck for a gas gun.
 
I believe the original intent of the cartridge was to replace 7.62x51 gas guns in certain USSOCOM units for particular CONOPS. They wanted something lighter, using the normal M4/M16 lower, and with faster follow up shots than 7.62x51, but without sacrificing the external ballistics of 308. Hence the comparison.

The 243 is a great round, but doesn’t let you load the longer high BC bullets. Same reason why USSOCOM went with 6.5 CM over 260. The 260 offered more powder capacity, but they wanted to future proof a bit for long bullet designs.
I see, that makes sense now. I’m a little confused as to why they saw the need to go the 6ARC route then when the 6.5 Grendel was already available. There’s more to these decisions than I am aware of from my narrow perspective, I am sure.

No, the 243 doesn’t let you load the highest BC bullets. Prior to knowing why the comparison is between 6ARC and 308, my point would have been that the 243 Winchester can push that same magic 108 bullet up to a few hundred FPS faster than the 6ARC in comparable barrel lengths. So I thought that should be the two we are comparing.
 
i would re-iterate this question as it was where i kinda stopped myself while looking at what to do with the last available ar15 lower.
it`s neither cheap nor widely available, that kinda makes it suck for a gas gun.
I spent a couple of years trying to find it. Bad timing with the pandemic shortage, I thought at first. Finally gave up when I decided I don’t think it’s going to catch on and be widely produced like I thought it would.
 
I spent a couple of years trying to find it. Bad timing with the pandemic shortage, I thought at first. Finally gave up when I decided I don’t think it’s going to catch on and be widely produced like I thought it would.
it is there, but not that i would love for a semi-auto brass eater.

i already have a 6 dasher where an every brass piece is a $1+.
 
… I’m a little confused as to why they saw the need to go the 6ARC route then when the 6.5 Grendel was already available. …

Yeah, not sure. It would have been an easier and faster option to field test. Maybe they did try it and decided they wanted to tweak it a little? Who knows.

I do think they most likely figured out all their requirements and Key Performance Parameters, gave them to Hornady, and Hornady did the development work. USSOCOM has unique funding opportunities for R&D and acquisition. So to them, it probably wasn’t any more work to have Hornady make a cartridge that better met their requirements. Taking a cheaper (no development) COTS solution that was 90% of their requirements wasn’t worth it. That’s all pure speculation though.

Whether they considered or tested 6.5 Grendel at all, I have no idea.
No, the 243 doesn’t let you load the highest BC bullets. Prior to knowing why the comparison is between 6ARC and 308, my point would have been that the 243 Winchester can push that same magic 108 bullet up to a few hundred FPS faster than the 6ARC in comparable barrel lengths. So I thought that should be the two we are comparing.

Yeah, it’s a totally fair comparison. It’s just in this particular case, they wanted a small frame receiver.
 
Who knows- perhaps 6 ARC could die on the vine but there are some specific reasons besides the standard size AR compatibility that give it some forward momentum:
  • It's a very efficient cartridge, as in the fps per grain of powder is good.
  • As mentioned, it's GTG for high BC projectiles.
  • Supposedly it has inherently good accuracy like the BR type cartridges.
  • Accuracy is optimal at sub-barrel burning velocities.
  • Many of the medium to high end barrel producers have several available options in this caliber and even a decent selection of in-stock barrels.
  • Both Peterson and Starline should be releasing brass in this caliber very soon.
For the cost of a decent barrel and bolt plus a couple mags I can simply repurpose my fugly CMP match AR and see how it does. I reload so the ammo cost will end up being cheaper than my .308 match loads.
 
I like this guy's load development process. Encouraging results from Varget-



I'll assume he's working with whatever barrel CMMG is using (probably not high end) and it's only a 20" barrel. I'll be working with a 24". I have that Compass Lake / Bartlein on order but in the meantime found a much cheaper Ballistic Advantage (BA) 24" to work with during the 12 week lead for the CL. Will be interesting to see what the CL Bartlein brings vs. the BA and any advantage of the +2 gas system length of the CL. The BA is a standard rifle length gas system. The BA barrel on my 6.5 Manbun AR is sub .7 MOA all day and sub .5 MOA with some effort.
 
I like this guy's load development process. Encouraging results from Varget-



I'll assume he's working with whatever barrel CMMG is using (probably not high end) and it's only a 20" barrel. I'll be working with a 24". I have that Compass Lake / Bartlein on order but in the meantime found a much cheaper Ballistic Advantage (BA) 24" to work with during the 12 week lead for the CL. Will be interesting to see what the CL Bartlein brings vs. the BA and any advantage of the +2 gas system length of the CL. The BA is a standard rifle length gas system. The BA barrel on my 6.5 Manbun AR is sub .7 MOA all day and sub .5 MOA with some effort.


That was an exceptionally accurate load. I would be happy with that. Velocity is a little low to get the most out of the cartridge, but accuracy makes up for it. I wouldn't want to go and buy a 6ARC based on these numbers. But I would like to see your results with 24". If you can get a sub moa group North of 2700 fps with an SAAMI spec load, I would say that is pretty compelling. You may also be able to squeeze a few more fps out of it by using an adjustable gas block to limit the amount of gas lost in propelling the bullet. With a +2 system it might not be that big of an improvement, bu it does help in my experience in shorter gas sysems. Looking forward to your results.
 
That was an exceptionally accurate load. I would be happy with that. Velocity is a little low to get the most out of the cartridge, but accuracy makes up for it. I wouldn't want to go and buy a 6ARC based on these numbers. But I would like to see your results with 24". If you can get a sub moa group North of 2700 fps with an SAAMI spec load, I would say that is pretty compelling. You may also be able to squeeze a few more fps out of it by using an adjustable gas block to limit the amount of gas lost in propelling the bullet. With a +2 system it might not be that big of an improvement, bu it does help in my experience in shorter gas sysems. Looking forward to your results.
One caveat-

I think it possible that I might end up with a load slightly over SAAMI spec. As far as I know, the spec is set at 52,000 psi which is the load data that Hornady provides for gas guns. 2700 fps from a 24" barrel was probably a bolt gun. Hornady gives bolt gun data for up to 62,000 psi. As usual I'll work my way up but suspect that I'd be slightly over 52,000 psi to reach 2700 fps as was the guy in that last video. That's why I'm getting a top shelf bolts- a JP Enhanced and a Wilson Combat. Both are made from 9310 tool steel.

Assuming I adhere to that 52,000 psi limit, possibly I could launch Berger 109's or 108's that will remain supersonic at 1200 yards with the right powder. I already use 2520 in 308 match loads and it's one of the higher velocity choices for 6 ARC. Probably more temperature sensitive than Varget but it performed extremely well for me at Camp Perry in brutal heat. Guys were literally dropping from the heat & at least one was hauled away in an ambulance. 2520 has worked well for me in colder temperatures as well, ~15F. If I'm shooting in a 'no sighters' environment I'll just have to see what are the cold barrel differences in velocity if any.
 
One caveat-

I think it possible that I might end up with a load slightly over SAAMI spec. As far as I know, the spec is set at 52,000 psi which is the load data that Hornady provides for gas guns. 2700 fps from a 24" barrel was probably a bolt gun. Hornady gives bolt gun data for up to 62,000 psi. As usual I'll work my way up but suspect that I'd be slightly over 52,000 psi to reach 2700 fps as was the guy in that last video. That's why I'm getting a top shelf bolts- a JP Enhanced and a Wilson Combat. Both are made from 9310 tool steel.

Assuming I adhere to that 52,000 psi limit, possibly I could launch Berger 109's or 108's that will remain supersonic at 1200 yards with the right powder. I already use 2520 in 308 match loads and it's one of the higher velocity choices for 6 ARC. Probably more temperature sensitive than Varget but it performed extremely well for me at Camp Perry in brutal heat. Guys were literally dropping from the heat & at least one was hauled away in an ambulance. 2520 has worked well for me in colder temperatures as well, ~15F. If I'm shooting in a 'no sighters' environment I'll just have to see what are the cold barrel differences in velocity if any.
Well now you’ve got me excited. I can’t wait to see what you end up with. That is a really good idea to go with the stronger bolts in that set up. That’s the weakest link. I believe lever and cfe223 will give more velocity than varget (I could be wrong). But the groups that he was getting in the video were some of the best I’ve seen. If you’re really going to take it out that far, it seems like varget may be the way to go. Maybe the 2520 will do it too. Keep us updated.
 
There was some discussion of this in the Sig Next Generation Squad Weapon, but I did not see an individual thread. I'm going to take a drink of this new Kool Aid flavor. There are a number of articles out there, but this one is a relatively quick read with some comparative 500 yard+ performance vs. the .223 and .308.

Everything You Need To Know About The 6mm ARC

Vs. 308, it has better long range ballistics, less than half the recoil, and is a 30% lighter rifle platform than a 308 AR. What's not to like? LOL I do have to hold my nose a bit as this caliber is a Hornady development and I think Steve Hornady is a jackass.

I plan to borrow the lower from one of my AR15 match rifles and will build an upper with the goal of having a long distance range toy. In the near future I'd like to take some courses at Ridgeline and after trying some 22NRL matches may step up to centerfire PRS matches. I already built an AR 6.5CM and Mrs. Mountain has a nice 308 Aero M5, so those calibers are covered. I thought about a 6CM rebarrel of my 6.5, but 6CM tends to burn through barrels more quickly and is a little hotter than I really need. I can always do that later for relatively short money but I'll probably just stick with the 6.5.

One of the logical digs against the 6 ARC is its lower velocity out of a gas gun. SAAMI specs are 2700 fps for a 108 grain projectile at 52,000 psi. I assume that's a bolt action 24" barrel. Hornady load data lists 52,000 psi as the limit for gas guns yet specs a limit of 62,000 psi for bolt guns. Like the 6.5CM AR I built, I'll use a high pressure JP bolt headspaced to my new barrel which will facilitate slightly hotter loads. Another point of attraction for me is that some of the best heavy projectile 6 ARC loads use Varget and 2520, of which both I use and keep stock in bulk. I'll use one of the better match barrel makers for a 24" (maybe a 22"?) barrel and run a rifle +2 gas system. Might take a couple months before I have my new barrel, but as I have done with prior 'builds' will post targets good or bad along the way.

I realize there are better performance options, but as far as I have seen thus far those options are all in the AR-308 platform. For the cost of a new barrel + bolt, new mags, and not much else we'll see how it goes...
There was some discussion of this in the Sig Next Generation Squad Weapon, but I did not see an individual thread. I'm going to take a drink of this new Kool Aid flavor. There are a number of articles out there, but this one is a relatively quick read with some comparative 500 yard+ performance vs. the .223 and .308.

Everything You Need To Know About The 6mm ARC

Vs. 308, it has better long range ballistics, less than half the recoil, and is a 30% lighter rifle platform than a 308 AR. What's not to like? LOL I do have to hold my nose a bit as this caliber is a Hornady development and I think Steve Hornady is a jackass.

I plan to borrow the lower from one of my AR15 match rifles and will build an upper with the goal of having a long distance range toy. In the near future I'd like to take some courses at Ridgeline and after trying some 22NRL matches may step up to centerfire PRS matches. I already built an AR 6.5CM and Mrs. Mountain has a nice 308 Aero M5, so those calibers are covered. I thought about a 6CM rebarrel of my 6.5, but 6CM tends to burn through barrels more quickly and is a little hotter than I really need. I can always do that later for relatively short money but I'll probably just stick with the 6.5.

One of the logical digs against the 6 ARC is its lower velocity out of a gas gun. SAAMI specs are 2700 fps for a 108 grain projectile at 52,000 psi. I assume that's a bolt action 24" barrel. Hornady load data lists 52,000 psi as the limit for gas guns yet specs a limit of 62,000 psi for bolt guns. Like the 6.5CM AR I built, I'll use a high pressure JP bolt headspaced to my new barrel which will facilitate slightly hotter loads. Another point of attraction for me is that some of the best heavy projectile 6 ARC loads use Varget and 2520, of which both I use and keep stock in bulk. I'll use one of the better match barrel makers for a 24" (maybe a 22"?) barrel and run a rifle +2 gas system. Might take a couple months before I have my new barrel, but as I have done with prior 'builds' will post targets good or bad along the way.

I realize there are better performance options, but as far as I have seen thus far those options are all in the AR-308 platform. For the cost of a new barrel + bolt, new mags, and not much else we'll see how it goes...

brownarc04.jpg
There was some discussion of this in the Sig Next Generation Squad Weapon, but I did not see an individual thread. I'm going to take a drink of this new Kool Aid flavor. There are a number of articles out there, but this one is a relatively quick read with some comparative 500 yard+ performance vs. the .223 and .308.

Everything You Need To Know About The 6mm ARC

Vs. 308, it has better long range ballistics, less than half the recoil, and is a 30% lighter rifle platform than a 308 AR. What's not to like? LOL I do have to hold my nose a bit as this caliber is a Hornady development and I think Steve Hornady is a jackass.

I plan to borrow the lower from one of my AR15 match rifles and will build an upper with the goal of having a long distance range toy. In the near future I'd like to take some courses at Ridgeline and after trying some 22NRL matches may step up to centerfire PRS matches. I already built an AR 6.5CM and Mrs. Mountain has a nice 308 Aero M5, so those calibers are covered. I thought about a 6CM rebarrel of my 6.5, but 6CM tends to burn through barrels more quickly and is a little hotter than I really need. I can always do that later for relatively short money but I'll probably just stick with the 6.5.

One of the logical digs against the 6 ARC is its lower velocity out of a gas gun. SAAMI specs are 2700 fps for a 108 grain projectile at 52,000 psi. I assume that's a bolt action 24" barrel. Hornady load data lists 52,000 psi as the limit for gas guns yet specs a limit of 62,000 psi for bolt guns. Like the 6.5CM AR I built, I'll use a high pressure JP bolt headspaced to my new barrel which will facilitate slightly hotter loads. Another point of attraction for me is that some of the best heavy projectile 6 ARC loads use Varget and 2520, of which both I use and keep stock in bulk. I'll use one of the better match barrel makers for a 24" (maybe a 22"?) barrel and run a rifle +2 gas system. Might take a couple months before I have my new barrel, but as I have done with prior 'builds' will post targets good or bad along the way.

I realize there are better performance options, but as far as I have seen thus far those options are all in the AR-308 platform. For the cost of a new barrel + bolt, new mags, and not much else we'll see how it goes...

brownarc04.jpg

Is the 6mm the downward step when you cant keep a tight manbun
 
Is the 6mm the downward step when you cant keep a tight manbun
The Bosley Clinic kicked me out when I said I wanted hair grafts to grow a manbun. 6 ARC is the Kojak caliber. [laugh]

Ammo delivered today. Cute little cartridges. Looks like a 221 Fireball that got fat. I'll take a pic next to a .30-06. They are a pretty compact cartridge.
 
6ARC is for wimps how can't handle the recoil of 6.5 Grendel! 6.5 Grendel is for AR-15 lover boys and girls who have no skills and cover up their inadequacy by pretending they're are shooting a more powerful 223.

Now, real men shoot 300 WinMag at 100yd, 408 Cheytac for 200yd and 50BMG at 300! Anyone who says they are shooting beyond 300yd are obviously lying.
 
Well, could ya have pinched any more pennies out of this package, you cheap @sshole Steve Hornady? Box is obviously not sized for these cartridges and they have tons of room to slop around inside it. The worst part is that the tips hang out of the bottom of the holder and can bang on the side / bottom of the thin box. I have seen many, many bullet tips get damaged in better packaging than this. The cartridges would literally be better off dumped bulk into some sort of pack. Do better, Hornady.

1679268057355.png

Rant aside, cartridges left to right are 6 ARC, .223, and .30-06.
 
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Well, could ya have pinched any more pennies out of this package, you cheap @sshole Steve Hornady? Box is obviously not sized for these cartridges and they have tons of room to slop around inside it. The worst part is that the tips hang out of the bottom of the holder and can bang on the side / bottom of the thin box. I have seen many, many bullet tips get damaged in better packaging than this. The cartridges would literally be better off dumped bulk into some sort of pack. Do better, Hornady.

View attachment 733742

Rant aside, cartridges left to right are 6 ARC, .223, and .30-06.
Whats the theory behind short fat cases?
 
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