Hornady 6mm ARC "New" cartridge

[gunsandgunsmithing]

I'm interested in the validity of the Hornady 52,000 PSI data, I want an AR style rifle for specific tasks and the medium pressure longevity is important to me.

AR hunting and controlled timed rapid fire without rapid throat erosion is important. The 52,000 PSI is an important aspect of that.

My Colt AR 15 A2 is a fabulous rifle, I simply need an AR that moves to the same cross application ballistics that 24 caliber bolt guns do for 22 caliber bolt guns.

I've been a 24 caliber shooter for nearly 40 years and have done and seen game taken with 24 caliber rifles people would not believe, I want a quality 24 caliber self loader without the short coming of high pressures. I'll leave the super customization to my Remington 700 in 6MM Remington.

You are in the company of people on this site, who have already done what Hornady is yet again taking credit for. This is the 3rd case that I'm aware of that they have either worked around or outright stolen from its designers. I'm not a fan.... and this cartridge fills no gap other than downloaded factory ammo for a platform that is deficient in design for it. But have fun!

 

[Kracken McGraw]

You are in the company of people on this site, who have already done what Hornady is yet again taking credit for. This is the 3rd case that I'm aware of that they have either worked around or outright stolen from its designers. I'm not a fan.... and this cartridge fills no gap other than downloaded factory ammo for a platform that is deficient in design for it. But have fun!

Is the third case the 6.5 PRC taken from the 6.5-284 ?

 

[ormandj]

You are in the company of people on this site, who have already done what Hornady is yet again taking credit for. This is the 3rd case that I'm aware of that they have either worked around or outright stolen from its designers. I'm not a fan.... and this cartridge fills no gap other than downloaded factory ammo for a platform that is deficient in design for it. But have fun!

They haven’t stolen anything, everyone can keep using their wildcats. If someone wanted to go through the effort and expense to get cartridges through the process to commercialize there is nothing stopping them. It’s silly to hold something against a company for trying to produce a cartridge to fill a need, and spending the money and time to commercialize it. If being similar to a commercial cartridge or wildcat was a crime, there should would be a lot less cartridges out there, wildcats included.

How many different ways do you think there are to produce a militarily and commercially viable 6mm cartridge that will function in an AR15 platform with only a bolt, barrel, and mag change?

 

[gunsandgunsmithing]

They haven’t stolen anything, everyone can keep using their wildcats. If someone wanted to go through the effort and expense to get cartridges through the process to commercialize there is nothing stopping them. It’s silly to hold something against a company for trying to produce a cartridge to fill a need, and spending the money and time to commercialize it. If being similar to a commercial cartridge or wildcat was a crime, there should would be a lot less cartridges out there, wildcats included.

How many different ways do you think there are to produce a militarily and commercially viable 6mm cartridge that will function in an AR15 platform with only a bolt, barrel, and mag change?

Is that you Xi Jinping?

 

[David Milisock]

You are in the company of people on this site, who have already done what Hornady is yet again taking credit for. This is the 3rd case that I'm aware of that they have either worked around or outright stolen from its designers. I'm not a fan.... and this cartridge fills no gap other than downloaded factory ammo for a platform that is deficient in design for it. But have fun!

This is the United States of America, NOTHING was stopping anyone from finding funding or putting up the financial backing to commercialize their own wildcat cartridge. The government wrote a specification in a request, Hornady Corporation simply had the resources to achieve the desired result.

The AR platform like all firearm designs have pros and cons. The AR like all self loaders suffers from rapid fire throat erosion, exacerbated by high chamber pressures. The nature of a self loading mechanism makes them more tedious to true up, they lack a strong camming action for lockup and have powder burn rate considerations due the the gas operation to list a few issues.

With my AR 15A2 with 68 grain projectiles from prone I can shoot 3" groups with the standard iron sights at 300 yards on a calm day. In the Delta configuration if I do my part it can print 1 1/2" groups at 300 yards.

If this pans out and in the future if shooters can go to any firearm store and buy AR 6MM firepower I find that impossible to be a bad idea.

 

[gunsandgunsmithing]

This is the United States of America, NOTHING was stopping anyone from finding funding or putting up the financial backing to commercialize their own wildcat cartridge. The government wrote a specification in a request, Hornady Corporation simply had the resources to achieve the desired result.

The AR platform like all firearm designs have pros and cons. The AR like all self loaders suffers from rapid fire throat erosion, exacerbated by high chamber pressures. The nature of a self loading mechanism makes them more tedious to true up, they lack a strong camming action for lockup and have powder burn rate considerations due the the gas operation to list a few issues.

With my AR 15A2 with 68 grain projectiles from prone I can shoot 3" groups with the standard iron sights at 300 yards on a calm day. In the Delta configuration if I do my part it can print 1 1/2" groups at 300 yards.

If this pans out and in the future if shooters can go to any firearm store and buy AR 6MM firepower I find that impossible to be a bad idea.

I didn't say it was a bad idea. I'm not going to debate whether or not resources make taking others' work and profiting from it is right or wrong here, either. We all have our own moral compasses and that just is what it is. I will just say that I believe shortening a 6AR by .025 or .030 was not done to enhance the cartridge in any aspect, but rather, to work around Robert Whitley, who is himself, an attorney.
Bad idea..no...In fact I shoot a 6 Grendel(6AR). I just don't tout it as my own creation. Nor did I see a need to modify it.
Nothing wrong with another option, especially when it will likely benefit our armed forces and include a factory ammo option for those that don't handload. Although, this cartridge is a handloader's dream, particularly in a bolt gun.

 

[David Milisock]

I didn't say it was a bad idea. I'm not going to debate whether or not resources make taking others' work and profiting from it is right or wrong here, either. We all have our own moral compasses and that just is what it is. I will just say that I believe shortening a 6AR by .025 or .030 was not done to enhance the cartridge in any aspect, but rather, to work around Robert Whitley, who is himself, an attorney.
Bad idea..no...In fact I shoot a 6 Grendel(6AR). I just don't tout it as my own creation. Nor did I see a need to modify it.
Nothing wrong with another option, especially when it will likely benefit our armed forces and include a factory ammo option for those that don't handload. Although, this cartridge is a handloader's dream, particularly in a bolt gun.

God is the only one who didn't base his work of of someone else's work. 17 years ago I wrote a series of work flow specific graphic art books, all my work was based on input, development and standards developed over years in the digital industry by many people.

My writing revolutionized how over 3 million users processed digital files for a specific software. I copywrite protected my first book and 4 weeks after publication it was translated into Chineses and illegally printed all over Asia.

I could have spent all the money I made on U.S. and European sales fighting the Chinese and in the end made nothing. That's life, I'm not going to whine, take my ball and glove and run home to momma.

Did Whitley patent the design? Was there any copywrite on documentation? If not it's moot. If so he may have a claim.

I'm not sure Hornady patented the design or just got a Militaty contract and then went through the process of getting a SAAMI certification as long as they didn't violate a patent or a copywrite they followed the law.

In any case they expended serious resources developing, testing and certifying the cartridge and if they shortened a case just to protect their return on investment that's smart business for them and me. If they fail to survive I as a shooter suffer significantly.

In any case you didn't see me, you or anyone else pony up to pay development and certification costs for Hornady.

Hornady, as all of us do, owe gratitude to those who came before. Those who have had or have not had success owe a little graciousness to the accomplishments of those who follow.

 

[Laurie]

Did Whitley patent the design? Was there any copywrite on documentation? If not it's moot. If so he may have a claim.

It's pretty pointless patenting new or wildcat cartridges (so-called 'proprietary' cartridges) unless working for a military development contract or suchlike. It usually has two results: if worth copying, other rifle builders and people in the small production end of the guntrade simply get around the patent by minor redesign to the shoulder angle and/or position, body taper and so on, close enough to give the same end result but far enough away to make the patent worthless; if it's a really good design that would take off it in the mainstream market it kills that chance as it guarantees its remaining a wildcat / proprietary number unknown except to a few aficionados and enthusiasts (as found here ). As I understand it, both results afflicted the Grendel until Bill Alexander (with Lapua help?) finalised the design and opened it up through SAAMI and CIP registration.

The classic English rifle builders selling to the wealthy end of the Empire trade before WW2 were obviously gentlemen selling vastly expensive products to other gentlemen. No 'gentleman' would seek to 'fiddle' somebody else's proprietary design to get around patents. It was interesting though that even in such an environment, there were some African dangerous game cartridges that were made available to everybody in the trade almost immediately without license fees. Other than the kudos of getting your name on the headstamp, I'm unsure of the motive for such apparent generosity.

 

[Gtscotty]

I don't understand what Hornady could possibly have stolen here. They took a look at existing wildcat designs that were themselves obvious modifications of the SAAMI standardized 6.5 Grendel. They then made some tweaks so that their chosen bullet design would work better at mag length, and they put together the official testing and SAAMI standardization package to have the the cartridge commercially standardized.

What did they steal? All ideas are heavily derivative from what came before, especially something simple like an 6mm AR/Turbo/LBC/Grendel/whatever. They made yet another derivative that fit their needs best and then actually put forth the work/expense to standardize it and get it to the point that lots of manufactures will now be offering rifles and barrels so-chambered.The only difference between them and what came before is that they put in the work and capital to standardize the cartridge. They robbed no-one and stole nothing, especially nothing unique of value. If they violated some kind of IP, I'm sure we'll hear about the lawsuit... but we won't, because they didn't, because most folks aren't stupid enough to try and patent or otherwise protect obviously derivative cartridge designs these days for the reasons cited in an earlier post.

 

[Gtscotty]

Apologies if I'm misconstruing your comment.

I think you're suggesting that powder is burning all the way down the barrel. My understanding is that powder is almost entirely consumed very close to the breech. Once the peak pressure is obtained-- all of the potential energy from a powder charge has been delivered. From there on out, it's just a depressurization event, as that fixed volume of high pressure gas is allowed to expand and cool. The larger the volume of gas stored at peak pressure (i.e., the later it occurs down the barrel), the more potential energy is stored. But also, the lower the expansion ratio because there's less trapped volume ahead of the bullet relative to that volume behind the bullet. This reduces efficiency. Consider that a 9mm handgun with a 4" barrel can deliver 325 lb-ft of muzzle energy from just 4gr of powder. A .223 will have ~3.5x the muzzle energy. But it will burn about 6x the amount of powder AND require a much, much longer barrel. What would those ratios be of comparing the .223 from a 4" barrel? Pretty abysmal for the .223.

If the pressure peaks earlier, then the expansion ratio is higher. Higher expansion ratio means more efficiency. But it also means a faster decrease in pressure and a lower AVERAGE pressure acting on the bullet in a long barrel. Bore size plays here also as it's a major element of the ratio of volumes before and after the bullet. This is why some small, low pressure calibers gain almost nothing from a longer barrel. (think 45ACP in a long barrel).

What I'm suggesting is that if you have 52ksi of pressure peaking when the bullet is 4" down the barrel (for example), then the amount of powder it took to get there is immaterial. We burn powder to produce gas, hot gas does the work. I'm also suggesting that you will not have powder continuously burning and contributing meaningfully to the work delivered to the bullet. This is why the pressure trace from Quickload has the shape it does--early peak, steady and logarithmic decline from there.

This decline is inevitable, you cannot "maintain the pressure for the entire length of the barrel" because powder is consumed early- there is no additional energy being delivered to the system after the early peak pressure.

You comment about a case "requiring a specific burn rate" is true of all cartridges. Every cartridge is either capacity limited or the burn rate is too fast to allow complete fill for a given MAP.

Exactly, folks get hung up on powder burn, % burned, how long it burns, etc. but it doesn't really matter directly. What matters for velocity is the area between the force curve on the base of the bullet (due to combustion pressure) and the curve of the forces resisting bullet movement (drag, friction, pressure from compressed air ahead of the bullet, etc). Sort of the integral of the difference between these two sets of equations over the time span the bullet is in the barrel. So holding other factors constant, if you increase the peak pressure, or the length of the elevated pressure curve (more slower burning powder) you increase the area under the force curve, increase the work done on the bullet and therefore velocity. It doesn't matter at all what percentage of powder QL (correctly or incorrectly) predicts will be burnt before the bullet leaves the barrel, all that mattes for velocity is the area under the curve.... bigger curve, faster bullet.

 

[Grimstod]

My understanding is that the shape of the cartridge, ergo the powder column, short height but specifically the diameter in relation to the bore diameter helps control the leading edge of the pressure curve. Also enhance and extend the pressure curve. I'm really anxious about that 52,000 PSI performance, if it's repeatable as documented by Hornady it's thevdata meow.

It will not come anywhere here to the repeatability of a PPC. Which is just a tinny bit shorter.

 

[ormandj]

It will not come anywhere here to the repeatability of a PPC. Which is just a tinny bit shorter.

Why? I'd be interested to hear your science/fact based perspective.

 

[David Milisock]

I have watched 3 Hornady videos, they have not said that this is the 6mm bench rest cartridge to win with. They have not said that you cannot win bench rest competitions with this cartridge.

What Hornady has said loud and clear is that for the AR platform this is a very uniform 6mm cartridge with consistent velocities and performance from legal barrels best from 18" to 24" but viable in 16" barrels. They have also said that moderate performance increases can be achieved by hand loading in bolt rifles. Hornady has also said from the AR platform the 6mm ARC is viable for varmints and mid sized game.

A 103 grain 6mm projectile at 2700 FPS, about 1,650 foot lbs in an accurate rifle will work well. If not one should not blame the cartridge.

I've decided that after the dust settles I'm getting a rifle with 2 matched uppers, a 16" with A2 sights and a handle if available and a 24" flat top with optics.

The question will be do I keep my Colt A2?

 

[David Milisock]

It's pretty pointless patenting new or wildcat cartridges (so-called 'proprietary' cartridges) unless working for a military development contract or suchlike. It usually has two results: if worth copying, other rifle builders and people in the small production end of the guntrade simply get around the patent by minor redesign to the shoulder angle and/or position, body taper and so on, close enough to give the same end result but far enough away to make the patent worthless; if it's a really good design that would take off it in the mainstream market it kills that chance as it guarantees its remaining a wildcat / proprietary number unknown except to a few aficionados and enthusiasts (as found here ). As I understand it, both results afflicted the Grendel until Bill Alexander (with Lapua help?) finalised the design and opened it up through SAAMI and CIP registration.

The classic English rifle builders selling to the wealthy end of the Empire trade before WW2 were obviously gentlemen selling vastly expensive products to other gentlemen. No 'gentleman' would seek to 'fiddle' somebody else's proprietary design to get around patents. It was interesting though that even in such an environment, there were some African dangerous game cartridges that were made available to everybody in the trade almost immediately without license fees. Other than the kudos of getting your name on the headstamp, I'm unsure of the motive for such apparent generosity.

It was a different time as long as you weren't John Taylor.

 

[gunsandgunsmithing]

I have watched 3 Hornady videos, they have not said that this is the 6mm bench rest cartridge to win with. They have not said that you cannot win bench rest competitions with this cartridge.

 

[gunsandgunsmithing]

Lol! They have said this and they have not said that...huh?
So, they haven't tested it enough...period.

I have tested a 6 Grendel and have won a nationals with it, against ppc's and 30br's, as well as others...but at pressures that typically will break ar15 bolt lugs withinn a couple of firings.

I've shot it as a 30, which the same basic design holds the 100yd 5 shot group record for..

I've done pressure testing and accuracy testing.

My 30 cal version was actually and originally designed to make major power factor in uspsa 3 gun competition. The USAMU dominated with it...to the point that they changed their rules! I call it a 30 Major, for obvious reasons.
Hornady picked it up for a short period and marketed it as a 30 Action Shooting! And while it was an apples to oranges comparison,...along came Remington, with another 30 cal AR15 round, called a 300 Blackout. Well...Hornady tucked their tail and hid, and did not produce more 30 Action Shooting ammunition, rather than to try and compete with 'Big Green" in that market.

I did my development with pressure testing equipment. Along the way..and very early on, I found tremendous accuracy potential and I went toward bolt rifles with it.

Keep in mind that AR15 bolt design has improved, slightly...but even with a 30 cal and equal bullet weight, I established 2,650fps with a 125gr bullet as max for reliable bolt life, vs a 6.5 Grendel and a 123 gr bullet at the same velocity.

Now, let's jump forward...Hornady wants me to believe that they can get reliability from a smaller bore, heavier bullet, with 100fps velocity increase.

Now, I'm not here to tell you what they can or can't do, but what I found that is counter to it.

You've made several posts on this 6 ARC topic and I know you're not a dummy, from reading them. I also know that port size, location and powder burn rates matter in this. But, I've tested up and down both sides, and found what I found. My prediction is that, IF this cartridge makes it to production at all...it will not be at the advertised speeds.

The cartridge is NOT the limiting factor. Rather, it is the platform they are designing it for.

Again, you are on a site that most things have already been done on. There are people here that know from experience. But I'm willing to learn if you have anything to offer. Just don't pipe sunshine where it never sees. What is your experience with this cartridge?

 

[Laurie]

@gunsandgunsmithing Great stuff! Really interesting. You obviously found the Grendel case plenty strong enough for some very high bolt-action pressures.

The 30 version I hadn't heard of (or then again, maybe have as these days I've forgotten about as much as I remember and I've read about so many wildcats and specialist numbers over the years). I'm assuming your 2,650 fps is in an AR-15 from the context and if a 20" barrel that's an impressive MV. (I have a 30BR old-geezer's plinker built as a parts-bin 'bitzer' starting with an old Paramount 4-lug Paramount 'Target Rifle' / Fullbore number and with admittedly only limited load development am running 125gn Sierra MKs at similar MVs from 23.5-inches out of the larger case. Incidentally, the engineer behind the Paramount's development from the Swing and former member of this forum Robert Chombart has sadly just died over in his native France.)

The 6.5 Grendel / 123 MV is more than OK too. Again, at an early stage of development in a Howa 'Mini' bolt-gun I'm generally running closer to the 2,400s than the 2,600s from 20-inches of factory barrel. However, I'm more interested in longevity than speed at this stage.

BUT ............ !! the ARC is already putting out seductive tentacles to rebarrel the Japanese / Canadian (MDT Oryx stock) piece to 6mm with a few additional inches out front. I have over 1,500 of those old Berger flat-base 'Low Drag' 6mm bullets from 60 odd grn up to and including nearly 1,000 of the 88gn model alongside more 95-108gn HPBTs than I'll probably ever find time to shoot. The LDs should be ideal for the little case in a suitably throated bolt-action and the old stirrings of 'let's try yet another new thing' are really making themselves felt, dammit! (The blandishments of Cigareets and Whuskey and Wild Wild Wimmen I can resist any and all day, but a sweet little six or 6.5 is as irresistible to me as a curvy woman to a compulsive skirt-chaser or a bottle of my native Scotch malt is to the compulsive spirits drinker. )

 

[David Milisock]

The cartridge was just released and as that is the case I'm researching. Balancing what has been said and has not been said by the manufacture against the testing done only on this exact cartridge and by so far a very few and none of them testing the exact platform in which the manufacturer has been advertising the cartridge for. Eliminating the conjecture and prejudice where I can. I only care what repeatable results can be documented on an AR 15 platform with a 24" barrel and smaller barrels unsurpressed at 52,000 PSI.

I'm looking for a working rifle. I have zero interest in any type of target shooting only field work. In plain word I'm looking for a multi upper single lower multi purpose hunting rifle. I have no illusions and have constructed a 450 magnum brown bear rifle on a Mauser action shooting 500 grain projectiles. So the 6MM ARC (if it works out) is not the only rifle required it will simply be the main work horse. My 6MM Remington has fit that need for nearly 30 years, I do not expect that type of performance from a self loading platform.

Your prediction is my concern and not in a small way but it's not the only one.

I've carried the M2 Carbine in M1A configuration, the CAR15, M16, M14 and many military bolt rifles in the standard and experimental cartridges from the early and mid seventies.

I am of the opinion tha EVERY cartridge developed for the AR platform outside the multiple 5.56 NATO specifications have so many cons that they outweigh any practical usefulness of their design. To me practical application is everything. Reliability, accuracy, ergonomics, lethality and universal availability of ammo are the main considerations.

My AR15 A2 is an excellent rifle, with 68 grain projectiles (found everywhere) and man sized targets at 500 yards on calm days with iron sights are SOP. However I have little use for that feature and the 5.56 is a limited varmint cartridge from an AR platform even with optics.

If the ARC works out a 16" with A2 iron sights can easily take deer at 250 yards. Switch to the 24" and optics and you have a a longer varmint reach and the accuracy for deer at increased ranges.

 

[Oso]

David - I think that the 6.5 Grendel is the better option for an accurate work rifle. Solid selection of 120gr-130gr hunting & target bullets (20gr-40gr heavier than readily available 6mm bullet selection). No issues for out to 600 yards hunting ethically, and much further (800-1000) for targets.

 

[RustyPin]

I'm fairly certain the perfect "Military" option was already found in the "6mm-SAW" which is duplicated by 6mm-SPC - 6mm Hagar, and it's capable of providing 30 Round Magazines.


You have to take a look at the original AR10 and see how it was downsized specifically for the 5.56. The same would have to be done to stretch that out a simple half an Inch, something easily done. Even giving the 5.56 2.5 inches of room and it becomes a potent long distance round, but it's still limited by .224 Bullets.

Don't expect the 2.26" box to provide the next replacement Military Cartridge - NATO. It's a far stretch yet it keeps getting repeated using words like "Government" and "Military" toot-toot, the ARC won't be adopted to replace the 5.56. We've heard of independent unit's that once adopted the SPC, the Grendel, the 300 Blackout and now the ARC and all that amounts to a hill of beans.



Until someone pony's up the One Million $ Civilian Magazine manufacturers want for the longer design it's a fantasy. This one will have to wait on a Military Contract. A couple Million really is chicken feed when it comes to the Federal Military Budget for the New Magazines. The last Men who designed the 5.56 & 6mm-SAW are all long dead from old age. Modern Politicians really don't seem to care about the life of a Basic Rifleman enough to bother. Thanks GOD someone had sense enough to dump that gutless 30 Carbine round, Lord knows it left piles of dead Marines in the Pacific.

Edit: Every shooter who has pushed his AR platform in 6mm with the .440 Boltface has reported shredded bolts way before the 1000 round mark. Any man touting this as a viable option for combat should be brought up on charges of Treason IMO. You're talking about useless rifles after a couple days of Combat. Sounds like snake oil salesman getting rich off the future deaths of Rifleman to me. Really it would be far more tasteful to sell this as Civilian plinker or something more akin to paper target killer than anything worth considering for realistic Military applications. Maybe they already have a New Rifle design that's super top secret that can withstand the stresses of the new ARC? We could keep thing realistic without passionate Hollywood John Wayne salesmanship that leans more towards fantasy than reality. How about an entry level Bolt gun for Junior using the 6mm ARC available at Wallyworld or Achademy? Sounds like some Junior Office MGR at the Pentagon gone full Yuppy swallowing this drivel full sinker when there's already available data dictating answers elsewhere.

(PS - if anyone has the cash, I've got the Blueprints gathering dust)