Grendel vs 308

[bigbear_98]

There was a thread on another forum where the op asked which was the better round for an ar15 or if he should get an ar10 in 308. He wants a longer range hunting rifle, but wants to stick to an ar platform. Since I went through the exact same journey, I posted this. There was of course a storm of ignorance as always. My data shows even with a considerable handicap, the grendel performs really well, but some people can't handle hat.

I was proud of my shooting, and like the data, so I figured I would post here and let some like minded people give their thoughts.


Here is my real world data on paper.

I have yet to shoot an animal with the Grendel. I am shooting a TBAC 30 BA on both rifles. I haven't hand loaded for the Grendel yet. I shot these groups to verify zero after taking the Rem apart to install a Timney, and taking the adjustable gas block off of the Grendel and installing a none adjustable block. I also removed and reinstalled the scope on the Grendel to shoot a group with a 223. Was very happy to see the zero hold true (Larue mount). I adjusted the 308 1/4 minute right for the second group. Wind was from the 6 and was shifting from 5-7.

I shot both rifles in an Accuracy first class out to almost 1200 yards. Both got there and were hitting 12" gongs. The Grendel drops to subsonic before the 308.
At 2500 DA and 89 degrees, the 308 is subsonic at 1059 yrds and the 6.5 at 984 yrds.

I am in love with both rifles....


308 is Rem 700 PSS
26" factory barrel
175 SMK 2674 fps hand loads

6.5 Grendel is a home build
20" Krieger barrel SAAMI 6.5 Grendel chamber with Maxim bolt
123 SST 2438 fps factory Hornady

Comparison



Grendel group 1



Grendel group 2



308

[cory]

Nice groups!

What projectile are you using? You should really be getting 2500 fps at a minimum 2550 fps realistically out of a 20" Grendel with 123gr bullets.

[bigbear_98]

Nice groups!

What projectile are you using? You should really be getting 2500 fps at a minimum 2550 fps realistically out of a 20" Grendel with 123gr bullets.

Those are factory hornady sst. I haven't reloaded for that rifle yet but have all the components. The factory stuff shot so well I bought all of the two lot numbers the two academy's local to me had. I still have a couple hundred. I will start load development soon.

[SHORT-N-SASSY]

bigbear_98,

Thanks for sharing your shooting report. Your Grendel shoots sweet!

Re your Ballistics Comparison chart, let's give that superb .308 Winchester "Bad boy" load an apples to apples comparison; i.e., 6.5mm Grendel Bolt gun, with handload (http://www.ar15.com/forums/t_3_121/5...age=1#i5517109) --- we'll still allow a 4" barrel advantage to the .308 Win.:

[Slappy]

The Grendel does not kick near as hard as the 308!! that is what I love about my 2 rifles!! BANG BANG!!

[bigbear_98]

The comparison you cite looks to be a low BC grendel buller at a modest velocity against a high BC 308 bullet in a very hot load. If you compare something like a 123 gr scenar at 2600 to that same 308 load you should see almost identical bullet paths from the two cartridges.

G7 numbers ran for both bullets.
Hornady sst is a low BC bullet??

175 smk is .243 G7BC. .496 G1 (<2800fps)

123 sst is ~.260 G7BC. .510 G1

[bigbear_98]

bigbear_98,

Thanks for sharing your shooting report. Your Grendel shoots sweet!

Re your Ballistics Comparison chart, let's give that superb .308 Winchester "Bad boy" load an apples to apples comparison; i.e., 6.5mm Grendel Bolt gun, with handload (http://www.ar15.com/forums/t_3_121/5...age=1#i5517109) --- we'll still allow a 4" barrel advantage to the .308 Win.:

Somehow your charts are not real. There is no way my 308 is going to get 1241 fps at 1000 yrds at sea level. With the atmosphere you have there knock off 100fps at 1k.

[stanc]

There was a thread on another forum where the op asked which was the better round for an ar15 or if he should get an ar10 in 308. He wants a longer range hunting rifle, but wants to stick to an ar platform. Since I went through the exact same journey, I posted this. There was of course a storm of ignorance as always. My data shows even with a considerable handicap, the grendel performs really well...

308 is Rem 700 PSS
26" factory barrel
175 SMK 2674 fps hand loads

6.5 Grendel is a home build
20" Krieger barrel SAAMI 6.5 Grendel chamber with Maxim bolt
123 SST 2438 fps factory Hornady

It's too bad you didn't say that was your intent. By comparing a 26" barrel, .308 bolt-action with hand loads to a 20" barrel, 6.5 Grendel AR15 with factory ammo, it appeared to me that you were trying to make the Grendel look bad.

[bigbear_98]

It's too bad you didn't say that was your intent. By comparing a 26" barrel, .308 bolt-action with hand loads to a 20" barrel, 6.5 Grendel AR15 with factory ammo, it appeared to me that you were trying to make the Grendel look bad.

Yeah. I think that was the point we got to and a few pointed out what I was trying to do. Oh well. I did say I loved the round a few times.

[cory]

The grendel chart posted by short-n-sassy shows a 139 gr scenar at 2700. I wouldn't expect the bolt to last very long with a 139 gr scenar at 2700. How does a 123 gr scenar stack up?

He was referencing a Grendel load in a bolt gun, but 2700fps with a 139gr projectiles has got to be in the 60ksi range.

[SHORT-N-SASSY]

Somehow your charts are not real. There is no way my 308 is going to get 1241 fps at 1000 yrds at sea level. With the atmosphere you have there knock off 100fps at 1k.

The "charts" you refer to are the results from dialing-in the default values, for Temperature (59 degrees) and Altitude (0 feet above sea level) provided in the Hornady Ballistics Calculator Page.

The results, below, using the Handloads.Com Ballistic Calculator, use the same values for Temperature and Altitude (NOTE: The .308 175-grain SMK Ballistic Coefficient, 0.496, is used in both programs, as well):

[bigbear_98]

The "charts" you refer to are the results from dialing-in the default values, for Temperature (59 degrees) and Altitude (0 feet above sea level) provided in the Hornady Ballistics Calculator Page.

The results, below, using the Handloads.Com Ballistic Calculator, use the same values for Temperature and Altitude (NOTE: The .308 175-grain SMK Ballistic Coefficient, 0.496, is used in both programs, as well):

I understand what Your "charts" are and they look impressive, but I see too many people posting misleading information. My information came from real life data.

[bigbear_98]

I was confused by the way this thread started out as a comparison of grendel in AR15 vs 308 in an AR10 followed by a comparison of a 308 bolt gun shooting hand loads to a grendel shooting factory ammunition.

That seems to cause heartburn for everyone. A buddy of mine has an 18" OBR in 308. I'll try to get it and do some testing with factory loaded ammo to get a closer comparison.

I was also thrown by the big difference between the trajectory I got from Sierra Infinity Suite compared to what bigbear_98 was getting from the JBM ballistics engine.

That is something I notice and see posted a lot. Data that just doesn't seem "right". Everyone trusts what the calculators say. They just predict.
I shot both of these rifles out to 1200 yards at an Accuracy first class. I had the Ballistic AE app, my whiz wheel (I had already gotten the data from a chrono set at 10ft, 100 yards, and 200 yards), and the Kestrel with Applied Ballistics all side by side. The apps gave the yardage our rounds were estimated to be subsonic at, then we shot to get a true data point. Eventually all of the calculators were reading the same. Everything is dead on now.


I think it is time to retire Sierra Infinity as JBM confirms what I've suspected all along, which is that getting a grendel to shoot to 1000 yards, while possible, is roughly equivalent to trying to get an M1A to shoot out to 1000 yards. Both can do it, but neither is ideal.

We were hitting 12" gongs at 1200 yards. If the rifle is shooting tight, the round is capable of getting there. I am anxious to try some handloads tailored to my rifle.

I've been playing with the idea of an AR10 build, but I would probably not go with a 308 in an AR10 either. I was thinking 260 remington or 6.5x47 lapua. I would be interested if anyone has any data on how an AR10 does with hot loads. What parts on the AR10 are going to start breaking as I begin pushing loads up close to max for the cartridge. Is the AR10 really able to push the same kinds of loads one would use in a bolt gun?

Someone else will have to respond as I have no real world experience with an AR10 or larger 264 cartridges.

Very nice shooting.

Thank you.

I do love shooting.

[SG4247]

I was confused by the way this thread started out as a comparison of grendel in AR15 vs 308 in an AR10 followed by a comparison of a 308 bolt gun shooting hand loads to a grendel shooting factory ammunition. I was also thrown by the big difference between the trajectory I got from Sierra Infinity Suite compared to what bigbear_98 was getting from the JBM ballistics engine. I think it is time to retire Sierra Infinity as JBM confirms what I've suspected all along, which is that getting a grendel to shoot to 1000 yards, while possible, is roughly equivalent to trying to get an M1A to shoot out to 1000 yards. Both can do it, but neither is ideal.

I've been playing with the idea of an AR10 build, but I would probably not go with a 308 in an AR10 either. I was thinking 260 remington or 6.5x47 lapua. I would be interested if anyone has any data on how an AR10 does with hot loads. What parts on the AR10 are going to start breaking as I begin pushing loads up close to max for the cartridge. Is the AR10 really able to push the same kinds of loads one would use in a bolt gun?

Very nice shooting.

I run my AR-10s in 6.5 x 47 Lapua at 2850 ft/sec using the 123 scenar for thousands of rounds with no issues. I have pushed it to 2950, but it is not a great load in typical 22" barrels.

Makes the .308 guys scratch their heads!

[rebelsoul]

Slappy got it right. RECOIL was a primary factor for me. I wanted three same caliber rifles that me and my very dainty daughters could hunt with. I first traded for a 308 AR-10, to much recoil for the girls, but a vast improvement over my Rem. 760 30-06. When we target shoot, I sneak in an empty chamber; they don't flinch when the hammer falls on their Grendels.