6.5 Grendel Review: 18″ Special Purpose Rifle

February 1, 2015 Bill Marr Cartridge Selection, Rifles 0

The 6.5 Grendel was created as a 200-800 yard cartridge to fit into a standard AR-15 magazine.  Based on the 220 Russian cartridge (the parent case utilized for the 7.62x39mm, 5.45x39mm and the 6PPC), the 6.5 Grendel is essentially a 6PPC necked up to 6.5mm with a no turn neck.  Since its introduction in 1975, the 6 PPC has dominated the 100 and 200 yard bench rest circuit because of its inherently accurate case design; a short powder column, small rifle primer, and long neck.  The 6.5 Grendel shares these attributes.

While the Grendel is a smaller 6.5mm cartridge in terms of case capacity (35.0 grain water capacity), and isn’t in the same velocity class as the larger 6.5mm cartridges, like the 260 Remington, 6.5×47 Lapua, and 6.5 Creedmoor; it does offer AR shooters  larger diameter bullets with better ballistic coefficients and improved performance at extended ranges when compared to .224 projectiles from a 223 Remington/5.56×45 mm NATO rifle.

 

The 6.5 Grendel (left), next to the 6.5x47 Lapua (center) and 308 Winchester (right).
The 6.5 Grendel (left), next to the 6.5×47 Lapua (center) and 308 Winchester (right).

To convert a 223 Remington/5.56m NATO AR-15/M16 M4 rifle to 6.5 Grendel, the barrel, magazine and bolt need to be changed.  All other parts are common with the 223 Remington system.  Factory ammunition is available from Hornady, Alexander Arms, and Wolf.

The majority of 6.5 Grendel load data is based on a 24″ long barrel.  I elected to go with a 18″ barrel 6.5 Grendel.

AR-15/M16 cartridge line up (left to right): 223 Remington/5.56mm NATO, 6.5 PCC virgin brass, 6.5 PCC fire formed brass, 6.5 Grendel, 6.8 SPC, 300 AAC BLK, 7.62x40 WT and 30AR. Note the relatively short (.145") neck on the 6.5 PCC.
AR-15/M16 cartridge line up (left to right): 223 Remington/5.56mm NATO, 6.5 PCC virgin brass, 6.5 PCC fire formed brass, 6.5 Grendel, 6.8 SPC, 300 AAC BLK, 7.62×40 WT and 30AR.

The 6.5 Grendel upper used in this post was built with the following parts from Brownells:

I was going for a Special Purpose Rifle (SPR) look on this upper.  The barrel I selected was a Brownells 1:8″ twist stainless steel barrel, it is 18″ long, with a mid-length gas system. The barrel included a head spaced bolt and is threaded 5/8-24.  I installed a Surefire brake on it.

I selected the Knight’s URX4 rail system for a hand guard.  The Knights URX4 accepts KeyMod accessories and has a low profile, perfect for this style of rifle.

The parts were assembled and mounted on my trusty Bushmaster lower.  The lower is equipped with a Geissele Automatics SDC trigger and Magpul CTR stock.  Even with the rattle-can lower, the assembled rifle still looked pretty cool (below).

A Nightforce 2.5-10x42mm compact riflescope in a Spuhr mount completed the package. This compact rifle scope may be my favorite offering in the Nightforce line.  The clear glass and readily accessible elevation, windage and parallax adjustments scream quality.

6.5 Grendel, Knights, Spuhr, Nightforce right 4

Since I hand load, I didn’t shoot any factory ammunition.  I ordered the following reloading components from Brownells:

For testing and evaluation purposes, I worked up 30 different loads with 5 different bullets and 2 different powders.  25 of the 30 loads used Hodgdon H322 powder, 5 used IMR 8208.  Bullets were the 140 SMK, 100 Scenar, 120 NBT, 136 Scenar-L and 120 Scenar-L.  CCI 450 primers and Lapua brass completed the cartridges.

Please note I avoid hot hand loads in semiautomatic rifles.  If you are wondering why, a few years ago I had a RRA rifle blow up a few feet from my face.  You can see what it looked like here: Rock River Arms Mid Length Carbine Kaboom!

6.5 Grendel, (left to right) 140 grain SMK, 100 grain Scenar, 120 grain NBT, 136 grain Scenar-L. Note: 120 grain Scenar-L not shown.
6.5 Grendel, (left to right) 140 grain SMK, 100 grain Scenar, 120 grain NBT, 136 grain Scenar-L. Note: 120 grain Scenar-L not shown.

All shooting was done prone, from a Harris bipod with a rear bag.  Targets were 2″ self adhesive orange dots with a distance of 100 yards.  I loaded 5 rounds of each cartridge.  Velocity data was collected with a MagnetoSpeed barrel mounted ballistic chronograph.  Groups were measured center-to-center.

WARNING: The loads shown are for informational purposes only.  They are only safe in the rifle shown and may not be safe in yours.  Consult appropriate load manuals prior to developing your own handloads.  Rifleshooter.com and its authors, do not assume any responsibility, directly or indirectly for the safety of the readers attempting to follow any instructions or perform any of the tasks shown, or the use or misuse of any information contained herein, on this website.

 

6.5 Grendel 18” BarrelNew Lapua Brass 2.200” OALWARNING: For reference, read disclaimer above, only safe in test gun
Load Bullet Powder Primer Velocity ft/sec SD Distance Shots Group size
1 140 SMK 21.0 H322 CCI 450 1837 29.4 100 YDS 5 NA
2 140 SMK 21.3 H322 CCI 450 1855 33.8 100 YDS 5 2.470
3 140 SMK 21.6 H322 CCI 450 1867 12.9 100 YDS 5 1.510
4 140 SMK 21.9 H322 CCI 450 1888 11.0 100 YDS 5 1.923
5 140 SMK 22.2 H322 CCI 450 1915 9.2 100 YDS 5 1.298
6 140 SMK 22.4 H322 CCI 450 1937 12.2 100 YDS 5 .923
7 100 Scenar 26.1 H322 CCI 450 2388 15.6 100 YDS 5 2.082
8 100 Scenar 26.4 H322 CCI 450 2409 29.2 100 YDS 5 1.990
9 100 Scenar 26.7 H322 CCI 450 2463 15.1 100 YDS 5 2.241
10 100 Scenar 27.0 H322 CCI 450 2504 15.0 100 YDS 5 1.715
11 120 NBT 23.8 H322 CCI 450 2057 6.8 100 YDS 5 2.013
12 120 NBT 24.1 H322 CCI 450 2095 8.8 100 YDS 5 1.307
13 120 NBT 24.4 H322 CCI 450 2119 11.2 100 YDS 5 2.497
14 120 NBT 24.7 H322 CCI 450 2159 12.8 100 YDS 5 2.092
15 120 NBT 25.0 H322 CCI 450 2186 6.7 100 YDS 5 2.309
16 136 Scenar-L 21.2 H322 CCI 450 1820 11.2 100 YDS 5 .876
17 136 Scenar-L 21.5 H322 CCI 450 1845 12.2 100 YDS 5 .777
18 136 Scenar-L 21.8 H322 CCI 450 1871 10.0 100 YDS 5 .837
19 136 Scenar-L 22.1 H322 CCI 450 1894 16.2 100 YDS 5 1.202
20 136 Scenar-L 22.4 H322 CCI 450 1933 18.6 100 YDS 5 .984
21 120 Scenar-L 23.8 H322 CCI 450 2093 23.0 100 YDS 5 1.017
22 120 Scenar-L 24.1 H322 CCI 450 2121 14.0 100 YDS 5 1.276
23 120 Scenar-L 24.4 H322 CCI 450 2156 9.1 100 YDS 5 1.379
24 120 Scenar-L 24.7 H322 CCI 450 2194 11.2 100 YDS 5 .825
25 120 Scenar-L 25.0 H322 CCI 450 2238 12.1 100 YDS 5 1.447
26 120 Scenar-L 26.3 IMR 8208 CCI 450 2228 17.0 100 YDS 5 1.420
27 120 Scenar-L 26.6 IMR 8208 CCI 450 2308 14.7 100 YDS 5 1.320
28 120 Scenar-L 26.9 IMR 8208 CCI 450 2323 9.7 100 YDS 5 1.512
29 120 Scenar-L 27.2 IMR 8208 CCI 450 2367 7.0 100 YDS 5 1.520
30 120 Scenar-L 27.5 IMR 8208 CCI450 2408 9.1 100 YDS 5 .977

A quick note on the 5 shot group sizes; many of the 1.5-2″ groups had the first three rounds touching, had I only shot three round groups, the results reported here would have looked significantly better.

Six of the loads shot under an inch at 100 yards.  While some loads opened up over 2 inches at this distance, average performance of 29 or the 30 loads (load #1 was used for zeroing and wasn’t measured) was 1.51″ (1.44 MOA).  8 loads shot sub MOA, and the best tested was .777″ (.742 MOA).

You’ll note the velocities I measured were substantially lower than those reported from 24″ barreled guns.  Look around the web for reports from 18″ Grendel users and you’ll see the numbers are similar to those reported here.  I do believe use of a different powder might have marginally improved results.

6.5 group 136 scenarI was hoping for better velocity from from a 18″ barrel- it just wasn’t happening with the loads I used.  In my head I convinced myself this would be a 6.5 Creedmoor in a standard-sized gas gun; I was wrong. The more I pay attention to posted velocities for the Grendel, the more I notice most of the guys who love this cartridge are running 24″ long barrels.  A longer barrel would certainly help a cartridge like this, with a relatively small case capacity, gain every bit of velocity it can.  Keep in mind, this cartridge is trying to do the best it can given the confines of a standard AR-15 length magazine.  If you want a cartridge that performs like a 6.5×47 Lapua, 6.5 Creedmoor or 260 Remington- you should buy one of those.

Had I stuck with three shot groups, the accuracy reported would have been significantly better (as previously stated, many of the larger groups had 3 rounds in one hole, with a flyer or two).  I like to shoot five shot groups and report everything, not just cherry pick.  I think it provides readers a more accurate picture of how rifles and cartridges actually perform.

I appreciate the value of the 6.5 Grendel in the AR platform.  Unless I had a reason for a short barrel, I would likely get one in 24″, especially if I was interested in long range shooting with it.  That doesn’t mean I don’t like the Grendel in an 18″ barrel, it certainly has its place, but the shorter barrel doesn’t realize the full potential of the cartridge.

In my opinion the 223/5.56 rifles are great all purpose guns, the 6.8 SPC would be my choice for pigs, and the 7.62x40WT is a great intermediate whitetail cartridge.  The Grendel offers a level of panache the others don’t.   It’s pedigree from the most accurate bench rest cartridge in the world, designed specifically to fit a stand sized AR platform, and availability of high quality brass, make it the thinking man’s choice.  Plus, the cartridge looks cool and it is a 6.5mm!

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