A History of AR Cartridges

Super-aerodynamic bullet

The 6.5 Grendel is a high-performance round, meant to be loaded with a super-aerodynamic bullet.

 

6.5 Grendel

Unlike the 6.8, the 6.5 came from the fertile mind of an inventing genius who wasn’t trying to invent a better jihadhi-busting round. Bill Alexander is one of those guys who can’t look at a part, mechanism, cartridge or other design without thinking of ways to improve it. The 6.5 Grendel is a simple-appearing cartridge. To define it in the simplest and most Bill-discounting terms, it is a 6.5/7.62X39 Ackley Improved. That is, it is the Soviet 7.62X39 case, necked down to 6.5, and with the shoulder blown out and sharpened, and the case walls straightened.

Lapua bullets

In the Alexander Arms cases, the 6.5 is leaded with Lapua bullets and uses small rifle primers.

Which grossly diminishes the work necessary to refine the dimensions of each. To give you one example, the case neck: how long? A shorter neck means a more-forward shoulder, and thus greater case capacity. More capacity means more powder, leading to more velocity, and greater range.

However, a shorter neck also means a less-pointy bullet, and thus a lower ballistic coefficient, leading to velocity drop at range. A shorter neck also means less tension on the bullet, and a greater likelihood of bullets loosening on feeding (being rudely shoved up the feed ramp) and a blown case from bullet setback. Some like to compare the 6.5 to the 6.8, and start an argument as to which is “best.”

They are more alike than they are different, despite the cases being so different. The two each start bullets in roughly the same velocity range, with bullets of similar weight, and the close-in performance is similar. (And both sides will hate me for saying so.)

The difference is in the long-range performance. A 6.8 bullet of 110 grains that starts at 2550 fps reaches the 500-yard line with 1515 fps and the 1,000-yard line with 980. A 6.5 Grendel, launching a 123-grain Lapua Scenar at 2650 fps, reaches the 500-yardline with 1890 fps and the 1,000 yard line with 1304 fps still on board.

For pretty much the same shoulder-thump, you get far better downrange performance, once you exceed the “typical combat” ranges of 300 meters.

Lapua bullets

Wolf makes 6.5 Grendel in brass cases, and this is really good practice ammo if you do not need the extreme performance of the Lapua bullets.

The 6.5 Grendel requires the same parts be exchanged to create it as the 6.8: bolt, barrel and magazines, although none of the three is cross-compatible between the 6.5 and 6.8. You pick one or the other, not something that does both.

Starting out, Bill Alexander patented and trademarked the cartridge and components, because the performance and accuracy were the big advantages of the system over other calibers. To devise something that performed and then allow anyone who wished to, to make one, and potentially diminish its performance and reputation,was not what he wanted. He has since licensed the round and designs to others.

Do you need a 6.5 (and when has need ever entered into the discussion)? Well, if you want to do long-range precision work, and don’t want the bulk and thump of the .308 in an AR-10 type rifle, yes. You can shoot to distance with a 5.56; the NRA High Power ranges have proven that. However, at 600 yards the 5.56 is not exactly the hammer of Thor. If you want to reach out and have some tap left, then the 6.5 is the next step up.

5 thoughts on “A History of AR Cartridges

  1. Diamondback

    Then there is the 6.8 SPC that delivers 90gr to 120gr bullets designed and engineered right to deliver 2 times the wound cavity of the 5.56 green tips and 77gr bullets. At 300yds and under it kills with authority with little recoil at 80% power of a 308 Win. But, since big industry did not design it in a research lab of their own, they let it die except for Hornady who was involved in the beginning.

  2. Diamondback

    Lets look at this:
    1. Remington wouldn’t keep the 450 bushmaster case making it- special and they own everthing.

    2. Remington didn’t advertise it or market at all

    3. A 30-30 can do what this does with a 20″ barrel / AK47 7.62×39 does 3/4 of it at $5 a box

    4. It has a 22″ barrel and costs $1000+ and then no reloading brass was released

    5. If it was necked down to 6.5mm it would be a winner, since it isn’t, it is a loser.

    Anyway you look at it Remington engineered a paperweight due to not releasing brass, etc.
    Remington gets an C+ for engineering and F+ for supporting and marketing it.

    If Remington had necked it down to 270 (0.277) to take advantage of all the 270 Win bullets or 6.5mm to take advantage of the 123 Amax and others Win/Win. Those calibers kill deer too and short and long range. But since Remington put their D team on it, it flopped miserably compared to just buying a 30 -30 Win with ammo for $300 from Chinamart and kill deer and hogs fine at 200yds and under – blue collar working man’s rifle. Even a bolt action Rem 700 ADL costs $350 and will kill with more fps and better hunting bullet selection at 1/3 the cost of the 30 Rem AR.

  3. gunslinger454

    There are a few other good AR15 rounds out there as well. As ‘theken101′ mentioned above, there is the .300 AAC Blackout which, if I’m not mistaken, is little more than a renamed & SAAMI approved version of the much older .300 Whisper wildcat round. Either one when loaded with a 110gr-115gr bullet basically replicates the ballistics of the 7.62x39mm round in a cartridge that is far more compatible with the AR15 platform, requiring only a new barrel.

    For the varmint hunters out there the .204 Ruger is a superb cartridge for sniping ground squirrels & prairie dogs, and, like the .300 Blackout, requires only a new barrel to work in an AR15. It’ll spit out a 32gr bullet at over 4,000fps and excels at exploding those prairie destroying little rodents at long range (as long as you can deal with the wind).

    One of the new cartridges that I find very interesting comes from Olympic Arms and was designed to exceed .308 Winchester ballistics in the AR15 platform. They call it the .300OSSM–Olympic Super Short Magnum–and it is essentially a Winchester Super Short Magnum case necked up to .30 caliber. Though magazine capacity is low, the cartridge holds a lot of promise for hunting & long range shooting with the AR15 platform.

    Then of course there’s the true big bores: the .450 Bushmaster, .458 Socom & .50 Beowulf. Any of the three will take any animal that walks on the North American continent, and they make dandy hog hunting rounds!

    My personal favorites are the .223/5.56, the 6.5 Grendel & the .458 Socom. The .300OSSM has also peaked my interest!

COMMENT