12.5 Grendel vs 14.5 6mm ARC your opinion counts

justagunguy13 said:

Does anyone here know what this scope is?

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Shoreglide said:

I just installed a Gen3 1-10 on my 12” Grendel. Hope to get some range time with it over the next couple weeks.

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LRRPF52 said:

Did you get the MOA BDC reticle or the Mil Grid tree?

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Shoreglide said:

It’s an MOA grid. I have Mil for everything else, but I took it in a trade where the deal was well worth it.

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LRRPF52 said:

For barrels, I would also look at Precision Firearms if you want a nice Criterion for a decent price, or want to step up to Krieger or Bartlein.

I’ve had great results with those, as well as many Lilja drop-in AR barrels.

I have 2x Criterion, 3x Lilja, 1x Faxon, 1x LaRue, 1x Rexus 14.5”, and something else I’m not remembering right now.

No matter what outdoor activity I’m doing, the 12” Grendel with TBAC suppressor gets thrown in the SUV because of how useful and compact it is. 2nd and 3rd ones to go with me for range trips and courses are the 17.6” Lilja and 18” LaRue.

For optics, I think that new Primary Arms 1-10x24 FFP looks really good, but I have no hands-on with it yet.

I’m using Vortex Razor Gen 3 1-10x on the 18” LaRue, and a GRSC Norden Performance 1-6x24 on the 12”.

I just wish I could get the new Vortex Razor AMG 1-10x that is part of the UK Contract KAC KS-1 carbines.

I have used a NF 1-8x NX8 on another 12” Grendel I built for a friend, and it’s a nice combo as well. Very compact and appropriate for the size. Seemed like it was easy for us to both shoot 1 MOA or less groups with it.

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LRRPF52 said:

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

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LRRPF52 said:

I used the data from Hodgdon’s and Hornady for AR-15 pressures.

For 6mm ARC, Hodgdon’s lists 14 powders under the 107gr SMK from a 24” barrel, the fastest being CFE223, AA2520, and LVR.

Hodgdon	CFE 223	2.260"		25.8	2,450	40,300 PSI		28.8	2,687	51,400 PSI		Buy Now
Accurate	2520	2.260"		25.0	2,395	39,700 PSI		28.5	2,672	51,300 PSI		Out Of Stock
Hodgdon	LVR	2.260"		25.4	2,400	37,700 PSI		28.2	2,669	51,800 PSI

For 110gr A-TIP, same thing:

Accurate	2520	2.260"		26.5	2,449	40,100 PSI		28.4	2,656	51,400 PSI		Out Of Stock
Hodgdon	CFE 223	2.260"		25.3	2,397	38,200 PSI		28.2	2,649	50,500 PSI		Buy Now
Hodgdon	LVR	2.260"		25.4	2,410	38,600 PSI		28.2C	2,660	51,200 PS

Those are the speeds I got from my 16” Grendel with 100gr 14 years ago without ever exceeding published max book data at the time. I’ve actually been chasing lower pressure with CFE223 and getting even faster speeds.

Here’s Hodgdon’s 24” data for 6.5 Grendel under 107gr SMK:

Hodgdon

CFE 223

2.250"

29.3

2,489

37,200 PSI

32.2C

2,740

47,500 PSI

Buy Now

Hodgdon

LVR

2.250"

28.8

2,525

35,900 PSI

31.7C

2,753

44,300 PSI

Here it is for the 100gr Nosler Partition (which is harder to drive into the rifling due to the partition wall inside, acts more like a monolith in that regard):

Hodgdon	CFE 223	2.240"		29.5	2,625	39,800 PSI		32.9	2,873	49,500 PSI		Buy Now
Hodgdon	LVR	2.240"		28.2	2,680	42,600 PSI		32.2	2,900	49,800 PSI

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Triple D said:

I’m a bit confused. Why would the comparison not include the 6mm 80gr eld-vt??

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LRRPF52 said:

I’ve been shooting Grendel since 2009, and shooting 12” since 2017. Just had it out last week with the kids, the month before, the month before that, etc.

What I’m finding is that the 100gr ELD-VT new load from Hornady really gives you close to or overlapping 6mm ARC performance. The fact that there are 124 factory loads in-production/distribution for 6.5 Grendel from a wide range of manufacturers also is really hard to overcome.

For target work, there are boat loads of different options, with my main one being 123gr ELD-M, but now I’m looking more at getting 100gr ELD-VT for target as well. It’s meant for slaying yotes, but puts down hogs as well.

For big game, 129gr ABLR, 105gr Cavity Back, 123gr SST, 85gr TREX, and a bunch of other factory loads will work within 200yds, especially on cow elk and mule deer. This is from a 16” with 123gr SST on a cow elk at 75yds, DRT, (not my kid):

For CQB, you have faster killing power with much larger wound channels with most of the 6.5mm bullets.

It really checks off all the boxes. My 12” Grendel is my most-preferred AR-15 I’ve ever owned, and I’ve been panic-buying AR-15s since the late 1980s.

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LRRPF52 said:

I’ve mainly been shooting 123gr ELD-M from my 12” Grendel suppressed as well. Shoots like that, 5rd groups into an inch off rear bag and bipod-supported. I prefer to just take it out to 400 or farther out of the gate and just hit steel at the same ranges I shoot the 18” Grendels. There’s not a lot of difference other than the 12” is a lot shorter and more easy to pack.

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LRRPF52 said:

If I was told I had to standardize all my AR-15s into one configuration, it would be 12” 6.5 Grendel suppressed.

If I could go back in time for my first Grendel, it would have been 12” instead of 16”. There is no practical difference between them downrange.

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justagunguy13 said:

Im pretty decided on the Grendel at this point especially out of the 12.5. Now its just a question which barrel will be good. The rainier ultramatch mod2 is an option I guess a custom krieger is an option from precision firearms. Just big price difference.

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LRRPF52 said:

Because I haven’t recorded my 80gr 6.5 Grendel velocities yet.

18” Grendel will be 3009fps with 80gr Hammer HT.

Looks like 14.5” Grendel will do 2940fps with 80gr.

12” Grendel should do 2782-2880fps with 80gr. My 12" averages 2698fps with 90gr TNT.

10.5” will be at ~2700fps (2654-2753) with 80gr.

Hammer bullets load data for 24” Grendel with 80gr Hammer HT is 3150fps.

Hornady 6mm ARC bolt gun data with 80gr GMX is showing max loads with the fastest powder at 3100fps.

Hornady factory ammo 80gr ELD-VT is showing 3020fps from a 24” test barrel at AR-15 pressures.

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LRRPF52 said:

Short story is Grendel has more case capacity and more piston area behind the bullet, more bore volume to evacuate pressure at a reasonable rate.

6mm ARC has less case capacity, less piston area, a tighter bore, builds pressure faster, so the window will be narrower for velocity but the same weight bullets have slightly-higher BCs. Advertised BCs seem to be optimistic across a lot of the SKUs and don’t match up with actual Radar data from Hornady.

Once you compare the Radar data with real world data, you see there isn’t much of a difference between 100-110gr between the two, especially with the Grendel’s additional mv at less chamber pressure.

You can also cut and paste the Grendel gas port diameters and locations from 5.56 when setting up a barrel, whereas you want the port farther from the chamber in 6mm due to bore ratio and resulting port pressure.

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st1650 said:

What do you get with 123 factory eldm with the 12in ? 2400 FPS ?

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Triple D said:

If you’re on the fence for a 6arc, the Rainier Arms 12” shoots the factory 105/108’s at 2365-2390fps iirc.

I’m not exactly a grendel fan. The performance didn’t match my expectations. I sold mine and built a 224Valkyrie. I’ve since added a 12” and 22” 6arc and a 22” 22ARC. I’ve been happy with the decision and downrange performance.

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justagunguy13 said:

Im pretty decided on the Grendel at this point especially out of the 12.5. Now its just a question which barrel will be good. The rainier ultramatch mod2 is an option I guess a custom krieger is an option from precision firearms. Just big price difference.

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rlsmith1 said:

The way I compare projectiles between calibers is to try to match BC rather than weight. This allows the larger calibers to take advantage of their larger bore diameter and vice versa for the smaller calibers. There are certainly times where unique bullets in a given caliber can push the envelope, but it's only a matter of time until those designs are available in other calibers with essentially the same performance (the biggest change being made to energy on target).

Personally, I would compare the 100 ELD VT in 6.5G to the 80 ELD VT in 6arc because they are similar bullets driven at the upper end of the velocity range. Will the ARC give up long range performance? Sure, but that's already understood as energy on target is less with the ARC (due to lighter bullet weight). Therefore, I would expect the ARC to be a better performer at closer ranges while the Grendel does better further out. It is up to the shooter which range is more important to them.

For me, I would rather a slightly flatter bullet inside 400 yds for coyotes at night, but you seem to prefer the performance at 700+ which lends better to the Grendel. This is not to say the Grendel is not a good performer at 400 (it has more energy for sure), but it may not be as flat which is more important to me as both cartridges will have enough energy on target for yotes.



Totally agree here, and as a general rule of thumb I try to set up my shorter barreled rifles with larger caliber cartridges to minimize velocity loss

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LRRPF52 said:

What I’m seeing is that for short range with lighter bullets of the same weight, Grendel also has more mv and flatter trajectory, it’s just that the 6mm has factory bullet options ranging in weights from 55gr-75gr that don’t exist in 6.5mm. Lowest 6.5mm weight is 80gr Hammer HTs.

In the 6mm ARC, COL is really short with the lightweight bullets, as it’s meant more for the 103-110gr class. I’ve always liked 6mm AR with 107s (simple neck-down from Grendel), but once I started seeing more what 100-110gr do in Grendel, my plans for a 6mm faded away.

For the yote hunters, you’re not going to see much difference as a shooter between 80gr Hammer HTs or 95gr V-MAXs in 6.5 Grendel vs 75-87gr in 6mm. Trajectories are going to be mostly academic at that point. In fact, you can match or exceed the 6mm mv from shorter barrels in 6.5 Grendel using LVR or CFE223, but the 6mms will make up for it at 400yds with BC. This comes into play for me when shooting suppressed and not wanting a lot of extra length on the carbine. We’re talking a spread in BCs between .365 to .406 G1, if advertised BCs mean anything.

A 14.5” Grendel with 80gr Hammers will do ~2900fps.

An 18” ARC will do 2800fps with the 80gr GMX and 2850fps with the 90gr ELD-X, per Hornady’s 18” AR max load data.

That 6mm 90gr ELD-X is a great bullet for short range hunting and long range target, supersonic out to 900yds from an 18” ARC.

The main varmint bullets for Grendel are:

90gr TNT
95gr V-MAX
95gr Varmageddon
100gr ELD-VT

Each one of those has a factory ammo option as well.

For 6mm ARC, you can hand-load a lot of varmint bullets ranging from 55-87gr. Factory ammo for varmints in the ARC include:

58gr V-MAX
75gr V-MAX
80gr ELD-VT
87gr V-MAX

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