Is 6AR Turbo ballistic equivalent to 6mmbr in bolt gun with 28-30 inch barrel?

[steveN]

Have a friend who shoots 6.5 Grendel in an AR gas rifle. I have a spare Savage short action receiver that we are considering building into a 6AR Turbo (6AR improved, which is formed from the 6.5 Grendel), strictly because we already have a good supply of the Grendel brass. On paper, the Turbo looks identical with 6mmbr as far as velocity with equal bullet weights, in long barrels. Any opinions, pro or con, in comparing these two? Will mainly be used for 600 yd./ short F class. Thanks for any info.

 

[15Tango]

I don't own either YET, I'm working on building one soon though. From my research they're neck and neck - 95s at about 3000 FPS +/- 30 or so FPS, same with 105s but at around 2880-2920 FPS.

When I get the thing put together I was going to use it for 600 yard F-Class. Run the numbers and those little 6MMs can run with other calibers that others wouldn't ever second guess for 600 yard. 6.5s and 7s will obviously beat them but at the price of recoil and they aren't a 6BR or 6T40 - two very accurate cartridges.

600 yard drop & wind w/10MPH wind -

105 Amax (2900) - 77" drop, 51" wind

155 VLD (2850) - 83" drop, 56" wind

Wayne

ETA, all the velocities out there for the 6T40 are from 26-28" barrels on ARs - if you run it in a bolt rifle and run the throat out so you can seat longer I bet you could gain 100 FPS without issue and if you're running a 30" barrel you might be able to run powders like R17 with the heavy bullets and get interesting results. If you do it, let us know how it goes.

 

[JERRYHM]

Here is my data on the 6mmAR-T40.
In a bolt rifle the MV can be higher.
I have shot many cleans in 600 yard HP matches.


6MMAR – TURBO 40 -------- 6.5mm Grindel necked down to 6mm.
August 16, 2008 Sacramento 100 yard Bench Rest - IRON SIGHTS Five Shot Groups - All are Berger Bullets

Powder – Load – Bullet –-- OAL –- MV – ES – SD - Group
RL15 30.1 -- B105s -- 2.443” –2882 – 05 –02 ---- 0.305”
RL15 30.4 – B105s -- 2.443” –2907 – 27 –09 ---- 0.545”
RL15 30.1 -- B108s -- 2.320” –2862 – 19 –07 ---- 0.475”
RL15 30.4 – B108s -- 2.320” –2896 – 07 –02 ---- 0.461” **** #1-600 Yard Load
H4895 28.5 – B90s ---- 2.270” –2876 – 20 –08 ---- 0.721”
H4895 29.0 – B90s ---- 2.270” –2922 – 13 –05 ---- 0.378” *** 200 Load with 90 and 95s
H4895 28.5 – B105s -- 2.443” –2808 – 11 –04 ---- 0.504”
H4895 29.0 – B105s -- 2.443” –2847 – 21 –07 ---- 0.848”
H4895 28.5 – B108s -- 2.320” –2780 – 07 –02 ---- 0.458” ***** 300 & #2-600 Yard Load
H4895 29.0 – B108s -- 2.320” –2814 – 19 –07 ---- 0.550”

 

[steveN]

Thanks for the detailed info. You are getting very impressive group sizes, especially for iron sights. I want to run a 30" barrel and 105 grain weight class bullets. Throating longer to gain an extra 100fps is appealing, too, as long as accuracy does not suffer. Most of my testing is limited to 300yds. (limited range) and I am striving for 10 shot groups of 1 inch (scope sight) to prove consistency. Thanks again for the helpful comments.

 

[NateG]

Jerry, are those loads with a bolt gun? I don't think I'd want to put over 30 grains of R15 under a 105 in mine...

(I'm guessing so since you're OAL for your 300 yard load is longer than the AR15 mag length?)