6mm ARC thoughts

[HaydenLane]

Any data on how the 6 arc does in a short barrel? The jtac elf owl pistol with 11” barrel is tempting me.

 

[Stinky Coyote]

You split hairs between the 6.5 Grendel and 6 Grendel...er I mean 6 Arc...when talking 123 eld-m and 108 eld-m comparisons of factory ammo. As they relate to BIG GAME HUNTING, it's easy to find the 6.5 Grendel is more well rounded on all parameters one could choose for 0-500 yard work. Most would agree 6mm is a niche diam. as well as sub 120 grains of lead when it comes to big game, so 2 wins for the 6.5 there, most would agree that hunting big game is a sub 500 yard game 99% of the time by 99% of hunters, another win there as the extra 150-175 yards of the Arc velocity increase is wasted. As for eld-m construction lots of argument those bullets shine with impact velocities between 1700-2400 fps...the 6.5 Grendel has that almost perfectly covered from barrel to 500 yards...like perfectly. The Arc is too fast imo, and a better choice for the long range, steel, or more varmint oriented crowds...just like most 6mm's shine for, this will be no different. You'll also get a little more efficiency from the slower 6.5 in the short barrel rigs as well.

If your world is inside 500 yards, stubby barrels, and Big Game is a primary menu item...the 6.5 Grendel is the top pick.

 

[Darryle]

I am wondering if you could cram a 6mm GT in one of the Howa Mini actions?

 

[hereinaz]

You split hairs between the 6.5 Grendel and 6 Grendel...er I mean 6 Arc...when talking 123 eld-m and 108 eld-m comparisons of factory ammo. As they relate to BIG GAME HUNTING, it's easy to find the 6.5 Grendel is more well rounded on all parameters one could choose for 0-500 yard work. Most would agree 6mm is a niche diam. as well as sub 120 grains of lead when it comes to big game, so 2 wins for the 6.5 there, most would agree that hunting big game is a sub 500 yard game 99% of the time by 99% of hunters, another win there as the extra 150-175 yards of the Arc velocity increase is wasted. As for eld-m construction lots of argument those bullets shine with impact velocities between 1700-2400 fps...the 6.5 Grendel has that almost perfectly covered from barrel to 500 yards...like perfectly. The Arc is too fast imo, and a better choice for the long range, steel, or more varmint oriented crowds...just like most 6mm's shine for, this will be no different. You'll also get a little more efficiency from the slower 6.5 in the short barrel rigs as well.

If your world is inside 500 yards, stubby barrels, and Big Game is a primary menu item...the 6.5 Grendel is the top pick.

I disagree having spent time looking at 6mm vs 6.5. At the velocities, the 6mm is as good or better. The bullets do their job whether 108 or 123. Most people don’t understand the stopping power of a bullet like Berger or Eldm. I blew apart a Coues at 730 yards with a 180 VLD. A 105 or 108 would have been plenty.

I am wondering if you could cram a 6mm GT in one of the Howa Mini actions?

Not in the Howa mini mags, but you can cram the 6BRA because of OAL.

 

[Stinky Coyote]

I disagree having spent time looking at 6mm vs 6.5. At the velocities, the 6mm is as good or better. The bullets do their job whether 108 or 123. Most people don’t understand the stopping power of a bullet like Berger or Eldm. I blew apart a Coues at 730 yards with a 180 VLD. A 105 or 108 would have been plenty.

I know of a 752 yard antelope with 6.5 Grendel from 24" with 123gr A-max, drt high shoulder shot, exited. So it can stretch beyond most's capabilities also. As I said...splitting hairs between these two. Have a friend who's hunted with 6-dashers for a long time, 500m whitetail buck on the fly and drt with 105's I got to help butcher and see first hand damage so yup, if you wanna play the long range game on little deer...then 6mm would be better choice for you but as I said...a niche choice. For most hunting and hunters are 500 yards or less, you get more bang for your buck from the 6.5 if not having 'niche' asks.

The 6mm 108 adds 140 yards to the 1800 fps impact velocity over the 6.5 123...but the 6.5 will still go 475 yards at 1800 fps impact and for hunting...that's more than enough for 99% of hunters. The 108 gets to 615 yards by the same comparison. I just used 95% of rated factory velocity and a random elevation to run the comparison.

Some other compares; 500 yard time of flight is .72 to .67 for the 123 to the 108. SD & BC are both high up the 21st century ladder for great penetration and flight to maximize the use of the measly 29.6 gr of powder. The 6.5 will be a bit more efficient in shorter barrels and also have longer barrel life. For a 6" mpbr the 6mm adds 16 yards so 249 yard mpbr 6.5 and 265 yard mpbr for 6mm. Slight edge to the 6mm here but after 250 yards most have the rangefinder out anyway. I'd rather have min 6.5 diameter and over 120 grains of lead...as most big game hunters would agree.

For any typical 6mm niche, like beyond 500 yards, a 'long range hunter' etc., long range steel banging, lots of varmint work, rarely anything bigger than deer and antelope...then there's lots to love about the 6mm version of the Grendel. Same reasons a guy will choose a 6mm Creedmoor over a 6.5 etc...they are typically niche reasons and it's well accepted the 6.5 the better 'hunting' choice. No different in this compare, just burning 29.6 instead of 43 grains of powder is all.

The 6mm Arc is an amazing cartridge, first commercially available small 6mm that can run with the BR's, PPC's, Dasher's etc. Finally a factory available small modern 6mm. 6mm will always be niche diameter that finds it's home in combo steel/long range/deer/antelope/varmints...the 6.5 will always be at home in big game hunting world.

I'm going to feel better about dumping the 6.5 123gr eld-m into the ribs of broadside moose at 400 yards than the 6mm 108gr, I know both will work, one will just feel a little less 'niche'.

 

[hereinaz]

I know of a 752 yard antelope with 6.5 Grendel from 24" with 123gr A-max, drt high shoulder shot, exited. So it can stretch beyond most's capabilities also. As I said...splitting hairs between these two. Have a friend who's hunted with 6-dashers for a long time, 500m whitetail buck on the fly and drt with 105's I got to help butcher and see first hand damage so yup, if you wanna play the long range game on little deer...then 6mm would be better choice for you but as I said...a niche choice. For most hunting and hunters are 500 yards or less, you get more bang for your buck from the 6.5 if not having 'niche' asks.

The 6mm 108 adds 140 yards to the 1800 fps impact velocity over the 6.5 123...but the 6.5 will still go 475 yards at 1800 fps impact and for hunting...that's more than enough for 99% of hunters. The 108 gets to 615 yards by the same comparison. I just used 95% of rated factory velocity and a random elevation to run the comparison.

Some other compares; 500 yard time of flight is .72 to .67 for the 123 to the 108. SD & BC are both high up the 21st century ladder for great penetration and flight to maximize the use of the measly 29.6 gr of powder. The 6.5 will be a bit more efficient in shorter barrels and also have longer barrel life. For a 6" mpbr the 6mm adds 16 yards so 249 yard mpbr 6.5 and 265 yard mpbr for 6mm. Slight edge to the 6mm here but after 250 yards most have the rangefinder out anyway. I'd rather have min 6.5 diameter and over 120 grains of lead...as most big game hunters would agree.

For any typical 6mm niche, like beyond 500 yards, a 'long range hunter' etc., long range steel banging, lots of varmint work, rarely anything bigger than deer and antelope...then there's lots to love about the 6mm version of the Grendel. Same reasons a guy will choose a 6mm Creedmoor over a 6.5 etc...they are typically niche reasons and it's well accepted the 6.5 the better 'hunting' choice. No different in this compare, just burning 29.6 instead of 43 grains of powder is all.

The 6mm Arc is an amazing cartridge, first commercially available small 6mm that can run with the BR's, PPC's, Dasher's etc. Finally a factory available small modern 6mm. 6mm will always be niche diameter that finds it's home in combo steel/long range/deer/antelope/varmints...the 6.5 will always be at home in big game hunting world.

You laid out the differences pretty well and fairly. I don't know that I would disagree with anything but your conclusion that the extra 12 grains is a meaningful difference. I just can't see it, but that is a choice based on feeling and preference. Its primarily why I don't really think it matters whether someone chooses 6.5 over 6mm. Pros and cons, they are so close that you like the extra weight, and that makes the difference for you. I like the reduced recoil and velocity.

Anyone reading this, should really appreciate how finely we split the hairs on this one. Hopefully they realize that there is no "right" or "wrong" and that they just pick the one that is easiest to get ammo and shoot.

It seems to me that the niche is growing as more and more people understand bullet technology and improvements in the skill sets in the shooting sports. Many Roksliders understand that the 77 gr TMK in .223 kills big game like bear, moose, and elk just as dead as the 300 win mag if done with the right bullet at the right terminal velocity. As you bump up in caliber, as long as you match the bullet to velocity, things will die as the distances stretch out.

I'd agree that the case capacity and the bullet size in 6.5 grendel and 6 arc make them pretty well indistinguishable ballistically and in effectiveness, as your data points out. The thing that the 6mm has is better sectional density/BC and higher velocity, coupled with slightly lower recoil. All that is my personal opinion why I think the Grendel case is really best suited for the 6mm, because it squeezes the last drops out.

To go down the rabbit hole a little further, if I had to build on a grendel case, I would take a 22 grendel in factory shooting the heavy .224 bullets over the 6mm ARC. The .224 Valkyrie is a little anemic. Consequently, I have a 22 grendel upper that I am building. You laid out the differences pretty well. There are pros and cons to both. I don't know that I would disagree with anything but your conclusion that the extra 12 grains is a meaningful difference. I just can't see it, but that is a choice based on feeling and preference. Its primarily why I don't really think it matters whether someone chooses 6.5 over 6mm. Pros and cons, they are so close that you like the extra weight, and that makes the difference for you. I like the reduced recoil and velocity. On my Howa Mini, I went back and forth on the 22 grendel vs. the 6 grendel variants to build. The 6 arc hadn't been released yet. In the end, the components and other things made the 6BRA my choice when my smith found I could open the Mini bolt face for the BRA.

 

[Stinky Coyote]

Ya the .22 cal thing still a limitation in many jurisdictions as 6mm or bigger is a minimum big game hunting diameter by law. As with most 21st century high bc/sd options there's lots of numbers to like out there, even in the .22 cal stuff, but loses major points as it can't go big game hunting in plenty of places even though the right numbers are there.

There's a ton of bullets to choose, you touched on a decent point, if all you want to chuck is about 100 grains of lead then the 6mm ARC is going to have the better bullet selection and numbers. Due to sheer volume of 6mm shooters in target sports etc. there is a really big selection of bullets. The 6.5 is no slouch there either but 6mm wins selection choices...reloaders have always had ability to maximize performance of any case.

I try to only compare factory offerings so that we ALL have access to the performance being discussed and majority of shooters are covered. In this case the two top eld-m's from hornady in their black ammo are incredibly close and peak efficiency available. For those who don't reload this is as good as it gets...we don't need to reload to get peak performance with these options. Same goes for Creedmoor options.

The 6.5 Grendel only makes sense if you're going to shoot 120 gr or higher imo, the 123 gr eld-m is what makes that cartridge for me. It's always the bullet first for me. If that bullet didn't exist I'd be all over the 6mm ARC with 108's and making it work just fine. The 123 eld-m is the first bullet to come along in the right construction type that hit all my minimums (bc/sd/diam/weight)., the fact that it got wrapped in the case that also hit my minimums for said bullet was utter perfection. It's no fat approach was ideal for my needs and desires of max versatility for a family who does steel/coyotes and lots of big game.

I do believe the 6mm-ARC will eclipse the 6.5 Grendel in popularity due to the popularity of 6mm in all the shooting disciplines and I believe it's great for the Grendel as well and will help increase it's popularity too. They will be cross shopped a lot. And both are big time winners, they are the 21st century champs of what 30 grains of powder can do and AR length/micro action platforms and will hold top spots in this category for a hundred years. Much like the Creedmoor's will do the same in the low 40 grain of powder arena standard short action. You can't go wrong when choosing between them.

 

[Unckebob]

Savage offers the 6ARC in a few different bolt action options. An inexpensive Axis, an inexpensive 110 Switchback (heavy threaded barrel), a tactical version with an 18" threaded barrel.

I got the Switchback and threw it in a chassis. It is crazy accurate and gives me velocities very close to my 243.

For long range hunting, I think the Axis (in a better stock) would be fantastic.

 

[yej0001]

I would imagine one burns the 6ARC barrel quicker than 6.5 Grendel...probably not a concern for a hunting rig though

 

[Unckebob]

I would imagine one burns the 6ARC barrel quicker than 6.5 Grendel...probably not a concern for a hunting rig though

I don't think the 6ARC would be hard on bolt action barrels. The velocity is very reasonable for the bore size since the cartridges is limited to AR 15 sized magazines.

 

[ThatDUDE]

I run a custom 6 BRA in a 20” barrel in a Howa Mini. I get 2850 right now with 95 grain VLD fire forming. The BRA has more case capacity than the ARC.

I like the 6 ARC better than 6.5 Grendel, but it is still anemic for me. Especially at that barrel length.

But, it will kill stuff dead. Great little carbine. I love my little Howa.

Do you have any more info on your build? Are you running a magazine or aftermarket hinged floor plate?

 

[hereinaz]

I am finishing it up over the next month or so and will post up build details. I actually pulled it out to weigh this morning but my batteries in my scale were dead…

I am running the DIP bottom metal for detachable mag in a Stocky’s carbon fiber. I opened the feed lips and cut them back a little and it had fed flawlessly.

My only problem was piercing primers until I had the pin reduced and bushed.

 

[Cody finch]

I am finishing it up over the next month or so and will post up build details. I actually pulled it out to weigh this morning but my batteries in my scale were dead…

I am running the DIP bottom metal for detachable mag in a Stocky’s carbon fiber. I opened the feed lips and cut them back a little and it had fed flawlessly.

My only problem was piercing primers until I had the pin reduced and bushed.

How do you use 6br brass in that mini? Do you turn the rim down or did you have the bolt face opened up ? Thank you Cody

 

[hereinaz]

How do you use 6br brass in that mini? Do you turn the rim down or did you have the bolt face opened up ? Thank you Cody

Smith opened the bolt face. Looks like a magnum bolt face in a regular action. Figured proof testing on a Grendel would mean it is strong enough for the BRA. I never push pressure or chase velocity, so I am comfortable with the risk.

 

[Cody finch]

Thanks for the update on bolt face, I am considering doing this mod. myself if I can get my smith to do it.