Best AR-15 caliber: 6.8 SPC vs. 6.5 Grendel

https://ammoseek.com/ammo/6.8mm-remin...

The most important question to ask when choosing between the 6.8 SPC (or SPC-II) or the 6.5 Grendel is, "WHAT IS YOUR APPLICATION & NEED?"

Are you hunting from short range (sub-300 yards) or using the gun for self defense?

Would a light weight platform (16" or less barrel length) be more beneficial?

Are you shooting bench rest and seek a longer barrel gun (20-24") to maximize paper punching performance at 500-1000 yards?

Do you need terminal ballistics at the desired point of impact in order to harvest game ethically, or are you just punching paper and steel?

If you willing to carry a 20-24" barrel gun and deal with those heavier platforms, are there other calibers with better ballistics and performance?

The purpose of this video is to provide objective scientific information about these two cartridges. The comparisons below are with standard 6.8 SPC loads, not the more optimized SPC-II. Using the optimized SPC-II chambering offer even more advantages over the standard 6.8 SPC, and it should be noted that SPC-II loads can be loaded or purchased from Druid Hill Armory for the improved SPC-II chamber.
https://www.druidhillarmory.com/home/...

For reloading either of these calibers, check out Cavity Back Bullets for great brass and bullets.
https://www.cavitybackbullets.com/

Using Hornady's published data for their SST round for both the 6.5 Grendel & the 6.8 SPC. I selected this round because it is only 3 grains of bullet weight difference, which makes comparison rather easy to illustrate a point.

6.5 Grendel w/ 123 gr Hornady SST fired from a 24" barrel is 2580 fps at the muzzle. Very few people actually use a 24" barrel when hunting, yet if someone does choose to do so, well, they could also use a 24" barrel with the 6.8, and again have more energy. When using a 16" barrel, there is a ~230 fps drop right at the muzzle.

The same 123 grain Hornady SST 6.5 Grendel round out of the 6.5 Grendel out of a 16" barrel.
At the muzzle - 2350 fps / 1508 ft-lbs
100 Yards - 2189 fps / 1308 ft-lbs
200 Yards - 2034 fps / 1129 ft-lbs
300 Yards - 1885 fps / 971 ft-lbs
By the time you are at 300 yards, the Gendel out of a 16" barrel drops below the desired 1000 ft-lbs for hunting white tail deer or other mid-sized game.

Now let's look at Hornady's data for the 120 grain SST out of the 6.8 SPC from a 16" barrel
At the muzzle - 2460 fps / 1612 ft-lbs
100 Yards - 2250 fps / 1349 ft-lbs
200 Yards - 2050 fps / 1120 ft-lbs
300 Yards - 1862 fps / 923 ft-lbs
The 6.8 is also below the 1000 ft-lbs of energy at 300 yards. Point being, the hunting application of these calibers need to be limited to 300 yards.

Even with the older SPC standard loads, the 6.8 has more energy at the muzzle and at 100 yards...which is important to the person selecting either of these firearms for close quarters combat or for hunting at shorter ranges. Out to 200 yards the two firearms are essentially tied, and at 300 the Grendel begins to show are more significant, but still slight lead...yet, we should recall this is the older SAMMI 6.8 spc factory loads. When loaded to SPC-II specs, something that is now available, the SPC-II's strengths over the 6.5 Grendel become more significant.

Now, drop down to a 12-14.7" barrel, and the data becomes even less favorable for the 6.5 Grendel...while the 6.8 begins to really shine. Here is the data for 12" barrels. Note: when using a 12.5" barrel, keep your whitetail hunting shots under 250 yards.

6.5 Grendel w/ 12.5" barrel using 123 gr Hornady SST
At the muzzle - 2280 fps / 1407 ft-lbs
100 Yards - 2119 fps / 1216 ft-lbs
200 Yards - 1963 fps / 1043 ft-lbs

6.8 SPC w/ 12.5" barrel using the 120 gr Hornady SST
At the muzzle - 2389 fps / 1508 ft-lbs.
100 Yards - 2181 fps / 1257 ft-lbs.
200 Yards - 1991 fps / 1047 ft-lbs

Here we see the 6.8 in the shorter barrel, which one might opt for in a self defense application, the 6.8 outperforms the 6.5 out to 200 yards when it comes to delivering energy into the target, but then again both rounds will drop below the "1000 ft-lb minimum" by the time they reach 250 yards.

The main point being here...if you want to reach out beyond 300 yards for hunting, get a round with not only long range trajectory, but also long range performance energy...meaning, a more powerful round than either of these platforms. Ballistic charts are of little importance if there is not sufficient energy transfer to ethically and humanely harvest the game...however, if you are seeking a light weight platform that delivers efficient performance at less than 300 yards, both of these platforms work, however, the 6.8 SPC shows not only some performance advantages over the 6.5 Grendel, but also has a few reliability and strength advantages as well.

To get the full potential of the 6.8, select the more common SPC-II spec chamber, and get ammo loaded to the SPC-II specs...and you will be even better off.