6mm ARC vs 6.5 Grendel Sanity Check

[LRRPF52]

I’ve been asking for someone to check my work on this, but really would like a second-look, preferably from someone that’s been shooting LR for 10 years or more and knows their way around ballistics programs and real-world results.

From 18” barrels, Grendel with the 100gr ELD-VT really beats the 6mm ARC 108gr ELD-M, even if we hand-load the 6mm 75fps faster than Hornady’s data up to 24” velocities from Hodgdon’s.

I’m using Hodgdon’s 6.5 Grendel load data for the 100gr Partition (which is harder to drive into the lands) with an average between their CFE223 and LVR data from 24” barrel (2873-2900fps), then run down to 18” velocity of 2750fps through a Grendel internal ballistics engine. I’ve personably loaded the 100gr NBT to 2675fps from a 16” Grendel as well before we had CFE223 or LVR data.

6.5 Grendel 18” barrel, 100gr ELD-VT, 2750fps, .226 G7 Hornady program, 6300ft elevation, 59˚F

600yds 3.7 mils drop 1.1 drift
800yds 6.0 mils drop/ 1.6 drift (592ft-lbs)
1000yds 8.8 mils drop/ 2.1 drift (436ft-lbs)

6mm ARC 24” barrel, 108gr ELD-M, 2650fps hand load, Hornady Doppler Radar Data, 6300ft elev, 59˚F

600yds 4.1 mils / 1.3 drift
800yds 6.8 / 1.9
1000yds 10.2 / 2.6

18” ARC data shows 2575fps max in Hornady’s manual. Seems about right if Hodgdon’s is showing 2650fps from a 24”.

That really kills the ARC in that weight class. ARC is still relevant with the 55-87gr bullets for varmint, but I’m just not seeing the attraction in the 100-110gr class. Let me switch to the 110gr 6mm A-TIP to see if it will do it....


24” 6mm ARC, 110gr 6mm A-TIP, 2650fps Hodgdon’s max data, Hornady Doppler program, same conditions:

600yds 3.9 drop / 1.1 drift
800yds 6.4 drop / 1.6 drift
1000yds 9.5 drop / 2.2 drift 433 ft-lbs

[lazyengineer]

Thanks for the detailed assessment - I look forward to the replies. My personal favorite detail about 6mm ARC is the ability to convert it into 6.5 Grendel so easily.

[biodsl]

The Grendel has a 125 fps advantage over the 6mm ARC with similar weight bullets?

I'm getting 2560 fps with the Hornady 6mm 105 BTHP with Lever out of a Lilja 16". I wonder if the 2350fps figure you've got is low.

[VASCAR2]

[LRRPF52]

The Grendel has a 125 fps advantage over the 6mm ARC with similar weight bullets?

I'm getting 2560 fps with the Hornady 6mm 105 BTHP with Lever out of a Lilja 16". I wonder if the 2350fps figure you've got is low.

[jonny rotton]

i recently built two 6arc uppers. one 16" from sixfive arms and one 12.5" faxon gunner barrel.
my velocities are as follows with hornady 105 bthp black. 16" 2515 fps, 12.5" 2402 fps. the elevation is roughly 3200'

[LRRPF52]

i recently built two 6arc uppers. one 16" from sixfive arms and one 12.5" faxon gunner barrel.
my velocities are as follows with hornady 105 bthp black. 16" 2515 fps, 12.5" 2402 fps. the elevation is roughly 3200'

[jonny rotton]

i am thinking that maybe i made a mistake in building the two 6mm arc uppers. i should have just bought a ton of 107 tmks and loaded a bunch of ammo. i have been saving all my factory brass for years now.

[StoneHendge]

Swap the Hornady 108 ELD-M with a G7 of .270 for a Berger 109 gr Long Range Hybrid with a G7 of .292......

[Zeneffect]

With the less than grendel case capacity and limited to mag length, aren't the 109s a touch long? What kind of velocity vs barrel length?

I saw an old article on accurateshooter or something that seems relevant to this discussion... looking for it.

https://www.accurateshooter.com/cartridge-guides/6-5-grendel-cartridge-guide/

Old and comparing against 6br but still..

[biodsl]

With the less than grendel case capacity and limited to mag length, aren't the 109s a touch long? What kind of velocity vs barrel length?

I saw an old article on accurateshooter or something that seems relevant to this discussion... looking for it.

https://www.accurateshooter.com/cartridge-guides/6-5-grendel-cartridge-guide/

Old and comparing against 6br but still..

I've been playing with the 115gr RDF in my Rebby Lilja 16" 6ARC. The RDF measures at 1.342, longer than the Berger at 1.277. Getting around 1MOA at 2490fps with LeveRevolution so it can be done. I bet the Berger is a more accurate bullet though. The 105 RDFs aren't very good in my barrel. I'm going to push them closer to the lands and see what happens.

Note: At standard pressure, this 115 RDF load is supersonic at 1150 yards. It goes trans-sonic at 900 yards with 479 lb-ft of energy. From a 16" barrel.

[Zeneffect]

I feel like you can approach that with the 130gr class of bullets in a 16" which would put you on par with the 115 in terms of BC. Interesting thought experiment. I feel like sierra is lying about the bc of the 105 blitzkings though. They were bucking wind way better and dropping far less than they should.

When the barrel goes sub 20" I kinda don't understand the arc at all vs grendel honestly. Grendel just makes more sense to me. Is the arc easier to load/more forgiving than grendel? I mean grendel is pretty easy. Shove enough lever in the case until you feel uncomfortable then send it with a projectile of your choice. Shoot sub moa all day. (Generalizing but you know it's about 90% accurate)

[biodsl]

I couldn't get the 130 RDF to shoot at all in my 16" AA barrel. However, the Berger 130 OTM did shoot around 1.5moa when loaded to 2.265". Got consistent velocities of around 2415 to 2420 FPS using LVR.

[lazyengineer]

I couldn't get the 130 RDF to shoot at all in my 16" AA barrel....

That's OK, nobody else can either.

[biodsl]

When the barrel goes sub 20" I kinda don't understand the arc at all vs grendel honestly. Grendel just makes more sense to me. Is the arc easier to load/more forgiving than grendel? I mean grendel is pretty easy. Shove enough lever in the case until you feel uncomfortable then send it with a projectile of your choice. Shoot sub moa all day. (Generalizing but you know it's about 90% accurate)

I agree. I believe the Grendel has better hunting capabilities. You can do things with 120 and 130 grain bullets the ARC just can't.