6mm ARC vs 6.5 Grendel

[new2mud]

I spent a year w the Valkyrie and I reload. While I only used it for hunting, I can say these things about the cartridge and long-range shooting and feel like I have some experience to back them up.

1) the twist rate on a lot of barrels, including some I have, was 1:8. Bullet stability calculators indicate that heavier bullets needed at least 1:7.7, and a few barrels were offered w 1:7.5. A guy I know owns a gun shop and had FITS getting a new build to group worth spit w 88-90gr bullets but grouped fantastic w 60 and 75gr. I told him 1:8 was too slow but he refused to listen. He swapped barrels and got it good enough to deliver to the customer...still makes me wonder about 1:8 twist, especially at the lower MV that cartridge has with the 88-90gr bullets.

2) high-for-weight/caliber BC is cute, but a heavier/larger high BC bullet will group better due to being less effected by wind/air currents.

I got sick of messing w carrying 60gr rounds for long-range (hunting...300-400yds w thermal) coyotes and 88gr for pigs. Too much hassle planning or changing mags. 64gr Nosler BSB seemed the answer. Hahaha. No. I finally got a Grendel and haven't looked back. 100gr ELD-M, 2,750FPS MV, 0.365 (or 0.385, can't recall for sure) BC. One bullet, one load for pigs, coyotes, and Bobcats at any range I'll shoot at.

Finally, relevant to the OP: I've not seen any MV (or load data yet) for the 6mm ARC other than some factory ammo info maybe. The Grendel will support 123gr ELD-M for sure (Hdy Black), but I think the max bullet weight for any available 6mm bullet will be 115gr. That's close. *If* you could find load data to show that the 115gr projectiles could be loaded in the 6mm ARC without killing powder room, then that might be a better choice as *maybe* the 115gr (or similar weight bullets) will have higher BC than the 123gr 0.264" bullets. But, the MV will have to be considered, too. Until load data is well documented, I think it will be hard to make an objective decision and choice.

FWIW, I dreamed and drooled about a 6mm cartridge for the AR-15 platform for a year (the whole time I was pushing marbles uphill w the Valkyrie) but the lack of SAAMI standard cartidges held me back. I reamed my own 24 Nosler barrel and bought a 6mm Predator (super nice guy to deal with selling/making those) but all after I'd chosen the Grendel as my daily cartridge. Now, w the 6mm ARC, a standardized cartridge, available...well, I found this post while seeking more info on it. And I've had a reamer on order from PTG for at least 6 weeks. That said to say this: I love the 6.5G...but the 6mm ARC could be what I've wanted all along.

HTH, YMMV, EIEIO.

--HC

Heck of a first post, HC. Welcome!

 

[HBoothe]

Heck of a first post, HC. Welcome!

Thank you. New here...not to the 'net. I try to be helpful and not full of bull.

--HC

 

[Cotay]

I spent a year w the Valkyrie and I reload. While I only used it for hunting, I can say these things about the cartridge and long-range shooting and feel like I have some experience to back them up.

1) the twist rate on a lot of barrels, including some I have, was 1:8. Bullet stability calculators indicate that heavier bullets needed at least 1:7.7, and a few barrels were offered w 1:7.5. A guy I know owns a gun shop and had FITS getting a new build to group worth spit w 88-90gr bullets but grouped fantastic w 60 and 75gr. I told him 1:8 was too slow but he refused to listen. He swapped barrels and got it good enough to deliver to the customer...still makes me wonder about 1:8 twist, especially at the lower MV that cartridge has with the 88-90gr bullets.

2) high-for-weight/caliber BC is cute, but a heavier/larger high BC bullet will group better due to being less effected by wind/air currents.

I got sick of messing w carrying 60gr rounds for long-range (hunting...300-400yds w thermal) coyotes and 88gr for pigs. Too much hassle planning or changing mags. 64gr Nosler BSB seemed the answer. Hahaha. No. I finally got a Grendel and haven't looked back. 100gr ELD-M, 2,750FPS MV, 0.365 (or 0.385, can't recall for sure) BC. One bullet, one load for pigs, coyotes, and Bobcats at any range I'll shoot at.

Finally, relevant to the OP: I've not seen any MV (or load data yet) for the 6mm ARC other than some factory ammo info maybe. The Grendel will support 123gr ELD-M for sure (Hdy Black), but I think the max bullet weight for any available 6mm bullet will be 115gr. That's close. *If* you could find load data to show that the 115gr projectiles could be loaded in the 6mm ARC without killing powder room, then that might be a better choice as *maybe* the 115gr (or similar weight bullets) will have higher BC than the 123gr 0.264" bullets. But, the MV will have to be considered, too. Until load data is well documented, I think it will be hard to make an objective decision and choice.

FWIW, I dreamed and drooled about a 6mm cartridge for the AR-15 platform for a year (the whole time I was pushing marbles uphill w the Valkyrie) but the lack of SAAMI standard cartidges held me back. I reamed my own 24 Nosler barrel and bought a 6mm Predator (super nice guy to deal with selling/making those) but all after I'd chosen the Grendel as my daily cartridge. Now, w the 6mm ARC, a standardized cartridge, available...well, I found this post while seeking more info on it. And I've had a reamer on order from PTG for at least 6 weeks. That said to say this: I love the 6.5G...but the 6mm ARC could be what I've wanted all along.

HTH, YMMV, EIEIO.

--HC

I find great joy in shooting my 6.5 Grendel's. I currently have four Grendel chambered ARs (12", 16", 18", and 20") and two Howa Mini Actions (20" LW in Boyds Stock; 20" HB in MDT Chassis). At first I dismissed the 6mm ARC because in theory I have everything covered with other calibers.

But then I realized that I have enough parts floating around to build two more Grendel rifles and I don't really need that. Since my lgs has 6mm ARC factory ammo in stock and I have 105gr and 108gr pills for my 6mm Creedmoor reloads, I figured why not?

I swore I wouldn't add another reloading caliber...oh well, who was I kidding?

 

[HBoothe]

I find great joy in shooting my 6.5 Grendel's. I currently have four Grendel chambered ARs (12", 16", 18", and 20") and two Howa Mini Actions (20" LW in Boyds Stock; 20" HB in MDT Chassis). At first I dismissed the 6mm ARC because in theory I have everything covered with other calibers.

But then I realized that I have enough parts floating around to build two more Grendel rifles and I don't really need that. Since my lgs has 6mm ARC factory ammo in stock and I have 105gr and 108gr pills for my 6mm Creedmoor reloads, I figured why not?

I swore I wouldn't add another reloading caliber...oh well, who was I kidding?

Lemme know where you find dies, please. I've done a little looking and they're not easy to locate. Maybe I did poor searching. And I just today got Internet access at the house...I've been relegated to using the #$%# cell phone directly or hot-spotting it to use the computer for short bits. I've been Internet handicapped!

I have a barrel ordered from CMMG (just today got an e-mail stating my order was backordered 10+ weeks) and a reamer ordered from PTG (ordered about 2 mos ago now, IIRC) but no blank...so I'm a ways out on having a rifle...but I'd like to have the dies already.

--HC

 

[CaptnC]

I got mine from Midway USA a couple months ago.

 

[HBoothe]

Lemme know where you find dies, please. I've done a little looking and they're not easy to locate. Maybe I did poor searching. And I just today got Internet access at the house...I've been relegated to using the #$%# cell phone directly or hot-spotting it to use the computer for short bits. I've been Internet handicapped!

I have a barrel ordered from CMMG (just today got an e-mail stating my order was backordered 10+ weeks) and a reamer ordered from PTG (ordered about 2 mos ago now, IIRC) but no blank...so I'm a ways out on having a rifle...but I'd like to have the dies already.

--HC

I have received all the components now. I have dies (direct from Lee), 2 Green Mountain 1:7.5 barrel blanks, the reamer, and a GO gauge. Still no barrel from CMMG.

Day before yesterday I cut the chamber on the barrel and affixed the barrel extension for the AR-15 platform. I have finished forming a bunch of brass (100+ pieces) today and I have loaded a couple of cartidges. Maybe tomorrow I will be able to take the time to shoot the thing and see what maximum charges will be for the various powders I'll be trying.

I didn't cut the barrel to length. Instead, I'm going to find the maximum charge I feel I can get away with for several powders (CFE223, Leverevolution, and PowerPro 2000 MR). Then, I'm going to shoot 2 or 3 shots per "group" over the chrono with that load as I cut the barrel down 1" at a time. I'd like to see what the velocity drop off is as the barrel gets shorter. The barrel will start at about 27" and will end at 16".

Where gunwriters seem to always gravitate to the heaviest bullet an AR cartridge can afford, I'm going for a "hunting" rifle and am looking in the 90-100gr range. The bullets I will be testing this barrel with will be Nosler 95gr BT. I want to balance velocity and bullet weight.

I will post the results here. Maybe tomorrow...maybe another month...or three. Got a lot of stuff going on in life.

--HC

 

[CaptnC]

I'm still waiting on a barrel!

 

[T3ninja]

I'm LOVING the 95 Berger classic hunter in mine (6predator) It's not a speed demon by any means but it's exceptionally accurate. ~2600 FPS with h4895.


So far I've tried
TAC
Varget
H322
Benchmark
And a few others

H322 is the king for me with 75 gr TNT

H4895 is the best so far with 95+ gr up to 105's

 

[HBoothe]

I'm LOVING the 95 Berger classic hunter in mine (6predator) It's not a speed demon by any means but it's exceptionally accurate. ~2600 FPS with h4895.


So far I've tried
TAC
Varget
H322
Benchmark
And a few others

H322 is the king for me with 75 gr TNT

H4895 is the best so far with 95+ gr up to 105's

*IF* I am recalling correctly, the 6mm Predator is made by the guy w AR15Performance.com. I have one. It shoots fast (high MV for load data) and it shoots very well (consistent groups). The only thing for me is that the barrel I have is 22", not useful as a run-and-gun AR. But the barrel I got from AR15Performsnce is good. And I had a great conversation with the guy I spoke to there (the owner, I think). The site showed it was not in stock but he said it was, updated the site and I ordered the barrel. Very good experience, all around.

That barrel shoots too good to risk messing it up by cutting it down....so I'll make a 6mmm ARC I don't mind sacrificing.

--HC

 

[T3ninja]

I have received all the components now. I have dies (direct from Lee), 2 Green Mountain 1:7.5 barrel blanks, the reamer, and a GO gauge. Still no barrel from CMMG.

Day before yesterday I cut the chamber on the barrel and affixed the barrel extension for the AR-15 platform. I have finished forming a bunch of brass (100+ pieces) today and I have loaded a couple of cartidges. Maybe tomorrow I will be able to take the time to shoot the thing and see what maximum charges will be for the various powders I'll be trying.

I didn't cut the barrel to length. Instead, I'm going to find the maximum charge I feel I can get away with for several powders (CFE223, Leverevolution, and PowerPro 2000 MR). Then, I'm going to shoot 2 or 3 shots per "group" over the chrono with that load as I cut the barrel down 1" at a time. I'd like to see what the velocity drop off is as the barrel gets shorter. The barrel will start at about 27" and will end at 16".

Where gunwriters seem to always gravitate to the heaviest bullet an AR cartridge can afford, I'm going for a "hunting" rifle and am looking in the 90-100gr range. The bullets I will be testing this barrel with will be Nosler 95gr BT. I want to balance velocity and bullet weight.

I will post the results here. Maybe tomorrow...maybe another month...or three. Got a lot of stuff going on in life.

--HC

*IF* I am recalling correctly, the 6mm Predator is made by the guy w AR15Performance.com. I have one. It shoots fast (high MV for load data) and it shoots very well (consistent groups). The only thing for me is that the barrel I have is 22", not useful as a run-and-gun AR. But the barrel I got from AR15Performsnce is good. And I had a great conversation with the guy I spoke to there (the owner, I think). The site showed it was not in stock but he said it was, updated the site and I ordered the barrel. Very good experience, all around.

That barrel shoots too good to risk messing it up by cutting it down....so I'll make a 6mmm ARC I don't mind sacrificing.

--HC

You're correct, that's the guy/barrel/chamber I'm referring to. I'm pretty sure mine is a 22" as well. I really love this setup. I'm sure I will catch grief if many people see this BUT, it's going to be going on an elk hunt in CO with me in a couple weeks. I hope I don't need to use it because it's a backup in case my custom 300 wm goes down. However, as small as it may be, I feel confident in it out to 150-200 yards on this

 

[HBoothe]

You're correct, that's the guy/barrel/chamber I'm referring to. I'm pretty sure mine is a 22" as well. I really love this setup. I'm sure I will catch grief if many people see this BUT, it's going to be going on an elk hunt in CO with me in a couple weeks. I hope I don't need to use it because it's a backup in case my custom 300 wm goes down. However, as small as it may be, I feel confident in it out to 150-200 yards on this

I'm glad I got it right. Good guy to deal with. I like to pass along positive experiences when I can.

Not gonna get any garbage from me about taking that for elk. Especially as a backup rifle. With the right bullet and careful aim, you should be fine, particularly at those "short" ranges.

Good luck!

--HC

 

[CaptnC]

You guys will really upset seeing that my minimum length that I want is 22" if I could get a 5R barrel but I have my heart set on 24" !

 

[HBoothe]

You guys will really upset seeing that my minimum length that I want is 22" if I could get a 5R barrel but I have my heart set on 24" !

Longer barrels can give greater velocity for a given load. But shorter barrels usually give tighter groups. The point behind me cutting this barrel down that I have is to see what the FPS cost per inch is. With the 6.5 Grendel, FPS drops about 25fps/inch in the 16-20" range. Not worth the extra length for what I do, but to someone else it might be. I will post the numbers here when I whack this barrel down as I shoot it.

--HC

 

[new2mud]

Longer barrels can give greater velocity for a given load. But shorter barrels usually give tighter groups. The point behind me cutting this barrel down that I have is to see what the FPS cost per inch is. With the 6.5 Grendel, FPS drops about 25fps/inch in the 16-20" range. Not worth the extra length for what I do, but to someone else it might be. I will post the numbers here when I whack this barrel down as I shoot it.

--HC

Really looking forward to the speed/barrel length test results.