The Atheris 6.5 Grendel ARC15 Tier 2 Upper Reciever is our next ODHA review project. Atheris Rifle Company of Salem, Virginia is a small company with a reputation for high-quality AR15 rifles, barrels, upper receivers and parts. I found Atheris during my quest for an accurate 6.5 Grendel upper receiver search.
Atheris’ sells three grades of AR15 upper receivers. I have a great 6.5 Grendel pig slayer, but I also wanted a more accurate barrel in 6.5 Grendel. After reading the Pew Pew Tactical review of the Atheris mid-level upper receiver, I decided it was time to pull the trigger on my next 6.5 Grendel project.
The Atheris ARC15 Tier 2 6.5 Grendel comes with a choice of barrel lengths from 16-24″ and I opted for the 20” Atheris barrel with a thread protector. It uses a mil-spec, forged upper receiver with Strike Industries dust cover, and also includes an Atheris ambidextrous charging handle. The bolt carrier group is a nitrided system with a 9310-steel bolt. Atheris offers a long list of calibers and options in each grade level shown in the table below.
The Atheris Upper features a slim free-floated MLOK handguard 15” long of their own design. The handguard has Picatinny rails in front of the receiver and on the end of the handguard toward the muzzle for attaching sights or accessories. You can add more Picatinny rails if needed using MLOK mounts.
So why another 6.5 Grendel instead of a different caliber if the Palmetto State Armory upper is so good? Well because the PSA upper is my Hog Hunting Rifle and 1-2 MOA is fine for that purpose. The new Atheris will be my coyote rifle. I want to be able to reach out and touch those yodel dogs and they are a lot smaller than a hog. So I will now have an upper with guaranteed sub-moa accuracy and a two-inch longer barrel for a little more velocity. I can mount my Sightmark Wraith Night Vision scope on the Atheris to make those long shots on a coyote at 200 yards day or night. Besides, I always like to have a backup gun.
The hard part of this project is the wait. Atheris basically does custom builds as you order. They tell you upfront that there is a two-three week lead time for an upper. Will it be worth the wait? We will see in about one more week.
The Atheris 6.5 Grendel arrived three weeks later and it is really sharp. The barrel is .75″ diameter from just in front of the receiver to the muzzle. The real beauty of this Atheris Upper is the quality of the inside of the barrel. I have never seen a rifle barrel with such a clean, smooth chamber, and the 5R rifling is perfectly cut and shines like glass. The chamber and bore of this rifle is a testament of Atheris quality.
Before I went to the range, I called Zach at Atheris and asked him about any break-in procedure for the barrel. I wanted to make sure I did everything right from break-in to cleaning. When I asked about the break-in, he replied, “It’s ready to go..just shoot it.” Then his reply about cleaning was, “you don’t need to clean it unless it starts to lose accuracy”, which he means shooing groups over an inch. He also instructed me to clean it with patches only and never use a brush in the barrel.
Typical 100 Yard Accuracy Of The
Atheris ARC15 Tier 2
So I followed his advice and here we go. I have shot 70-80 rounds so far, and none of the factory Hornady ammo nor my hand loads shoots groups of more than an inch. Hornady Black shoots best at close to 1/2″. Nosler and Hornady hand loads also shoot just as well.
When I went from an 18″ to a 20″ barrel, I was expecting all my loads to increase in velocity by about 50-75 fps. Both the Hornady factory loads (Black and the SST) did jump up 75 fps. Just what I was looking for, 2500 fps hunting loads. Accuracy has improved over the PSA 18″ barrel also with all the loads.
My only disappointment so far is that my hand loads have had almost no increase in velocity in the longer barrel. The first load I tried was 29.0 grains of AA2520 with a 123 Hornady SST bullet. Accuracy improved in the 20″ Atheris barrel but velocity only increased by 10 fps to 2360 fps. Velocity of 100 grain Amax loads with AA2230 were almost the same also.
The velocity of the 123-grain handloads is plenty fast enough and accuracy is great, but I wish I could find a powder that would get my 90-100 grain bullets up to about 2800 fps.
First Hunt with the Atheris 6.5 Grendel
My first successful hunt with the Atheris 6.5 Grendel was a hog hunt. After finding him in the pre-dawn darkness with the Pulsar Axion Thermal Monocular, I was able to stalk close enough to use my hunting light attached to the scope to get a 75-yard shot. The load was a Hornady 123 SST @ 2500 FPS.
Still waiting on my Sightmark Wraith Night Vision Scope to make hunting a lot easier.
6.5 Grendel Hog Hunt
My GO-TO 6.5 Grendel Varmint Load
New load today with Alliant Power Pro Varmint (PPV) produced outstanding results with the Speer TNT 90 grain HP. 32 grains of PPV produced 2800 fps in the 20″ barrel and shot about 1/2″ groups at 100 yards. This is not a max load so the primers are not flattened as much as factory ammo. Zeroed 1.5″ high at 100 yards puts it dead on at 200 yards. I put 8 straight shots in the center of the 3″ steel at 200. This will definitely be my coyote load for the Grendel. Another plus is that this load shoots to the same point of aim as the Hornady Black 123 grain ammo.
UPDATE: I used the Speer TNT 90 grain HP on my last two hunts. One to take a coyote at about 100 yards and a close shot on a hundred-pound hog. Both were DRT shots. The little Speer 90 HP shot completely through the hog’s neck area without breaking up. Think I will start shooting these for hogs and coyotes in the Grendel.
| Weight/Bullet | Powder Charge | Velocity | Primer | Remarks |
|---|---|---|---|---|
| 123 Hornady SST | 2500 | 1 MOA | ||
| 123 Hornady Black | 2475 | 1/2" | ||
| 123 Hornady SST | 29.0 AA2520 | 2360 | CCI | 1/2" |
| 123 Hornady SST | 28.0 IMR8082 | 2450 | CCI | 3/4" |
| 123 Hornady SST | 29.0 Power Pro Varmint | 2425 | CCI | 1" |
| 100 Hornady Amax | 31.5 AA2520 | 2700 | CCI | 3/4" |
| 90 Speer HP | 32.0 Power Pro Varmint | 2800 | CCI | 1/2" same POI as 123 |
5R Rifling of the Atheris 6.5 Barrel
5R rifling is a relatively new type of rifling developed by Barrett Obermeyer. It features five lands and grooves instead of an even number, usually 4 or 6 opposing lands and groves (see figure 1 above). 5R lands are also a different shape with sloping sides to prevent bullet deformation as the bullet is squeezed into the bore (figure 2). 5R rifling also reduces powder fouling and material build-up at the corner of the grooves which reduces the need for cleaning.
I can not confirm that 5R rifling is, in fact, better than traditional rifling. I can confirm that my Atheris barrel and my Smith & Wesson MP15 barrel, both of which have 5R rifling, are very accurate (sub-moa) and they rarely need cleaning. One of the specific reasons I chose Atheris is because they offer 5R rifling in their barrels.
ARC15 Tier 2 Upper Receiver Specifications
Atheris Rifle ARC15 Tier 2 Upper offers shooters high-quality features for hunting and long-range shooting. I especially like the 5R rifling, the adjustable gas block and a sub-moa guarantee.
- Atheris Forged Mil-Spec Receiver
- Atheris 416R Stainless Steel Barrel w/ 5R Rifling
- Guaranteed Sub MOA (1″@ 100yds)
- 1:8 Twist
- Atheris Black Nitride BCG
- Atheris 15″ MLOK Handguard
- 12.5″ Barrel comes with 11.5″ Handguard
- Ambidextrous Charging Handle
- Adjustable Gas Block
- Strike Industries Dust Cover
- Thread Protector
| Caliber | Barrel Length | Twist | Gas Length | Thread Pattern | Gas Block Size |
| .223 Wylde | 16 | 1:8 | Mid | 1/2×28 | .750 |
| 18 | 1:8 | Mid | 1/2×28 | .750 | |
| 300 AAC | 16 | 1:8 | Carbine | 5/8×24 | .750 |
| 6.5 Grendel | 16 | 1:8 | Mid | 5/8×24 | .750 |
| | 18 | 1:8 | Mid | 5/8×24 | .750 |
| 20 | 1:8 | Rifle | 5/8×24 | .750 | |
| | 22 | 1:8 | Rifle | 5/8×24 | .750 |
| 24 | 1:8 | Rifle | 5/8×24 | .750 | |
| 7.62×39 | 16 | 1:10 | Carbine | 5/8×24 | .750 |
| 6.8 SPC | 16 | 1:12 | Mid | 5/8×24 | .750 |
| 18 | 1:12 | Mid | 5/8×24 | .750 | |
| 20 | 1:12 | Rifle | 5/8×24 | ||
| 224 Valkyrie | 22 | 1:7 | Rifle | 5/8×24 | .750 |
| 24 | 1:7 | Rifle | 5/8×24 | .750 | |
| 50 Beowulf | 16 | 1:20 | Mid | 49/64×20 | .875 |
| 18 | 1:20 | Mid | 49/64×20 | .875 | |
| 450 Bushmaster | 16 | 1:20 | Mid | 3/4×24 | .875 |
| 458 Socom | 16 | 1:14 | Carbine | 3/4×24 | .875 |
| 6mm Grendel | 20 | 1:8 | Rifle | 5/8×24 | .750 |
| 22 | 1:8 | Rifle | 5/8×24 | .750 |
Atheris – 1/2 MOA Upper Receivers For $549!
I am extremely happy with the Atheris 6.5 Grendel Upper Receiver. It is all I could ask for in quality and accuracy. This upper shoots everything under 1 MOA and most everything 1/2 MOA with both factory and hand-loads with the 100-123 Hornady and Nosler loads I tested.
The overall quality of the fit and finish and the components used are superb. Everything is made right here in the USA and top-notch. The Atheris barrel, although it is marketed as a mid-tier barrel, is as good as most match barrels. Beautifully machined chamber, mirror polished bore, and superior workmanship set this upper receiver apart from the masses of AR uppers you will find on most rifles.
I highly recommend Atheris if you are looking for a quality AR15 upper receiver. At $549, I doubt you can beat their quality anywhere.
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