About 900 yards for 5.56mm.

When J.D. Jones designed the 300 Whisper, the intention was an efficient cartridge with a heavy bullet for close range sniper work. The original intent was to use 200+ grain bullets for their terminal energy out to around 200 yards or so, using a suppressor to prevent giving away the sniper's position. The intent was also for the cartridge to work in the existing AR-type rifle. The added 8" twist rate helps to stabilize the long, heavy bullets.

However, the 300 Whisper was not intended for use as a "long range" caliber. The 308 or 7.62x54 fills that niche, and lately the 50 BMG. I think the 6.8 was more or less one company's failed attempt to sway the military to use a larger, heavier cartridge that falls somewhere between the .223 and the .308. Happens all the time, politics you know. After all it was mostly politics that swapped us from the M-14 to the M-16. The M-14, as fine a weapon as it was, was only issued for a few years, while the rest of the world used (and still uses) FN-FAL's chambered in 7.62x54.

There is nothing wrong with the 6.8 SPC, as a matter of fact it's a fine cartridge. It's capable of astonishing accuracy at much further ranges than most of us are capable of shooting. I don't particularly want one or need one, that's why I chose to build my AR in 300 Whisper. Mostly because of bullet selection, just as you stated in the first place, not for any sort of long distance shooting. I also don't plan to pack a couple of hundred rounds of ammo into the woods with me when I go hunting with it.

Obviously most of the commentors here have not actually used the 6.8, especially to kill stuff................

We shoot hundreds of animals a year on the ranch in TX, mostly with AR platform weapons chambered in (listed in order of effectiveness):

.30 Rem AR
6.8 SPC II
7.62x40
300 Whisper/Blackout
5.56

After thousands of rounds down range and over 100 hog/deer kills with it I can assure you the 6.8 SPC is the best and most effective all around cartridge for hunting that will fit in the AR-15 platform. It's killing power is vastly superior to the 5.56 with any bullet including the very effective Barnes 62gr TSX. It gives up a little to the .30RAR at under 150yds, but it better all around with it's flatter trajectory, especially when using caliber specific bullets like the Barnes 95gr TTSX and Nosler 100gr Accubond.

I like my 300 Blackouts and especailly my 7.62x40, but they are 150yd cartridges in the real world of hunting.

If you want to learn more go to the 68forum ................

BTY, we have NO function issues with C-Prod or PRI 6.8 mags !!!! Our 6.8s are just as reliable as our 5.56 guns.

I'll agree, I love my 300 Whisper, but it does not have the effective range of the 6.8. Here in Mississippi however, the 300 Whisper is a very good choice. I don't personally own a 6.8, but like I said, there certainly 'aint nuthin' wrong with it! The 6.8 would be a good choice also, I just like fooling around with the 300 Whisper!

Yep, if someone's looking for "range" as well as terminal energy, there are much better choices than the 300 Whisper like the 6.8, 6.5 Grendel, and now the 300 Olympic SSW, just to name a couple.

Ha!, I am sitting here with 18 stitches in my arm and not able to run my new mill or reload ammo, and was thinging about building a 30HRT off a howa or rem when I saw this.

I agree, unless you hunt on a power line or have a corn field, here in Ms. "especially the coast where I am" the whisper is the perfect choice.

The 7.62x39 is one of my favorite cartridges. However, it's just not as versatile as the 300 Whisper. The relatively extreme taper of the case body limits the versatility of the cartridge. It works well for reliability in the original rifles that it was designed for, the SKS and AK47, but you'll notice that the factory offerings are mostly limited to the 2 bullet weights, and those are .310 - .311 bore.

Since I am a handloader, I ordered a custom barrel in 7.62x39 with a .308 bore. I figgured that the .308 bore would open up a whole world of options for a very common cartridge. I was sorta right! However, most loads that would be considered safe in a very similar cartridge as far as case capacity, the 30 Herret, will go overpressure in the 7.62x39. The tapered case causes a higher rearward thrust, and in my barrel, resulted in the action getting stuck and hard to open.

The 300 Whisper, in comparison, has a relatively straight wall case below the neck. This allows the bullets to be pushed to higher velocities than would be expected, and allows for the use of very heavy bullets, both in subsonic as well as supersonic loads.

If you use you imagination....take a 7.62x39 as a parent case, expand the case walls out almost straight, and chamber it in a 6.5 diameter bore and Viola!, you get a 6.5 Grendel. Take the same thing and make it a .308 bore and you get a 30 AR (sorta), etc. and so on....

Using an AR sized rifle for four legged critters like boar, give me a 6.8

Using an AR sized rifle for two legged critters that are also hunting you, give me a 5.56

I like them all.

I have 5.56s, 6.8s and a 300/221 with a tp555 bbl.

I whole heartedly agree with the analysis that the whisper-like cartridges are intended for ranges of 150 yards or so, and that the 6.8 is a much better hunting cartridge than the 5.56.

When I decided to go with the 6.8 versus the Grendel ... it was because I have a nice Mauser in .264 Win Mag and seldom hunt beyond 300 yards with an AR. Was also concerned abt the potential of bolt failures with the Grendel (which HAVE been reported!).