6mm AR, 6.5 Grendel or 6.8 SPC

[davidm5803]

Just would like some input on peoples preference on these three calibers (6mm AR, 6.5 Grendel, 6.8 SPC) in an AR-15 platform and why?

 

[Klong]

I have the 6.5 Grendel and the 6mmAR. The 6mmar is the most accurate, but cost more too. The 6mmAR will be the one I keep!

 

[15Tango]

I have a Grendel but in a short carbine, not exactly the type of stuff we talk about here. I really would like to get a 6MM T40 upper someday though. A 105 VLD at 3000 FPS is no joke and all you need to compete. 6.8 is pretty pointless to me, I know there are a few guys on here that love it and are working on improving it. The cartridge is long and skinny though and bullet seating at mag length is really going to cut down on case capacity, not as big of an issue with the 6MM AR/T40 or Grendel. Oh, and compare the BC of 6MM & 6.5 bullets to .277, it's not really fair.

I can vouch that the Grendel is really fun though but it's a really peaky cartridge - everything can be fine working up a load until all of a sudden it's too hot with hardly any increase in charge. Not trying to scare you, but it's a cartridge you have to work up and slowly.

Wayne

 

[pcrowe]

I shoot Robert Whitley's 6mm turbo 40 imp. in highpower xtc. It has the 28" Hart 1x8 tw barrel with the thick walled upper. It's very accurate and easy to load for. Lapua brass, RL 15, cci primers. For 200yds- Sierra 70 MK @ 3050 (mild load). For 300yds-95 MK @2920 (stiff load). For 600yds-107MK @ 2850 (stiff load). They all are approx. 1/2 moa loads. Gives me no excuses. I have two uppers and on the 2nd barrel on one, they work, very good quality, you won't be dissapointed.
Phillip Crowe

 

[Celt]

I've shot the 6mmAR in highpower competition for two years now.....highly recommend it. The 6.5 Grendel, in Mr. Whitley's words, "....wants to be a 6mm....." I agree.

 

[DHD]

It's a good question. As always, my $.02.

I would rule out the 6.8 unless you want a shorter range gun.

I have an AA Overwatch 6.5 and I do find the cartridge to be peaky. You got to work up slow. I have not found that I can get the chrono numbers with any of the 123's. I can get the 107 SMK to 2720 with no problems using 8208.

I plan to try a 6mmAR pretty soon as I have a lot of brass and like the numbers on it.

If I was to pick one, I would go 6mmAR....

 

[15Tango]

I have not found that I can get the chrono numbers with any of the 123's.

I haven't done a lot with 120 class bullets in my Grendel but with the 129 SST I was able to hit 'book' velocities with AA2520 but only that powder.

If the OP's going to use this rifle for any sort of accuracy shooting the 6mmAR or 6mmT40 can't be beat.

Drop to 600 yards -

6mmT40 - 105 AMAX @ 2950 - 74 inches

6.5 Grendel - 123 Scenar @ 2600 - 96 inches

6.8 SPC - 115 SMK @ 2550 - 135 inches
I used the factory load info for a velocity on the SPC, I don't know a lot about it.

The 6.5 Grendel and 6mmT40 are somewhat close on wind to 600 yards but the 6mm shoots flatter and at half the cost - 105 AMAXes are around $18 per 100 on Powdervalley and 123 Scenars are $33 per 100. There are cheaper bullets for the 6.5 like the 123 AMAX at around $25 per but the BC is only .510 if I remember right so you're going to give up something to go cheaper on the 6.5. With the 6MM you can get away with cheap and not give up on performance. So if you want to shoot a lot . . . Yeah, 6mm.

Wayne

 

[flatlander]

Dittos on going with the 6mmAR or AR Turbo or 6 RAT. I've got a custom build 18" bbl'd. 6.8SPC, and aside from the fact that it satisfied my curousity about the SPC cartridge, I don't have much use for it, nor the desire to keep it.

OTOH, I was very pleased with the results I got out of a 28" Bartlein 1:7.8tw. in 6 RAT on a spacegun built for NRA XC HP. Accuracy was great with S70MKs @ 200, Berger 90s @ 300, and Berger 105VLDs at 600. Function & reliability were 100%.

The reason I'm speaking of the RAT in the past tense is that I just sold the upper a couple of days ago - have built two (R5 & RTS) Elsieo tubeguns, and will be running them instead of a gasgun in HP matches. Nothing at all against the 6RAT - I'm just perverse enough to enjoy the challenge of shooting a stick shift in the rapids, and when the wind kicks up, the RTS in 6.5x47 will shoot inside any cartridge that the AR15 chassis can handle comfortably.

I have no experience with the 6.5 Grendel - aside from forming RAT cases out of it. But I agree with those who feel it doesn't have enough case capacity for 6.5mm bullets, and works much better when necked down to 6mm.

 

[JohnO]

I have two 6mmRAT space guns and one in a bolt gun. My only complaint is the inconsistancies in the magazines. I have shot .223 AR's for years and never had an alibi string due to a faulty magazine but I have had a few with C-Products 6.5 Grendel magazines. The rifles are quite accurate.

 

[Scott Harris]

6mmAR in an AR-15 chassis that you want to shoot precisely at the longest ranges. I think an AR-10 chassis is better suited to push the 6.5mm and larger bullets at competitive velocities. For a hunting rifle, the 6.5 or 6.8 would be fine, but for competition, I think the 6mmTurbo is as good as it gets for AR-15.

 

[15Tango]

Is there anybody out there selling just 6MMarT40 or 6MM Rat barrels w/extension and bolt?

Wayne

 

[flatlander]

Holliger will sell you a 6RAT bbl. w/extension & bolt.

 

[15Tango]

Has anybody compared the 6 RAT to the 6 T40? Do they both retain the same body taper as the Grendel?

Wayne

 

[Recko555]

Here's another place that chambers the 6RAT with Satern barrels.
http://www.accurateandreliablerifle.com/products.html#anchor_262

 

[15Tango]

Cool, thanks.

I'm debating between the 6t40 and 6RAT still, from what I'm seeing the 6t40 is has 38 grains water capacity vs the 6RAT's 37 so I'm leaning toward the 6T40 but I haven't heard anything back from R. Whitley yet about if he'll sell just a barrel/extension/bolt combo without being in one of his built uppers. Nothing against his work, just the fact it'll cost me double to buy it complete. If he won't do it I'll have to go with a 6RAT then.

Wayne