6mm AR should not be confused with 6mm ARC.
| 6mm AR | |
| Origin: | United States |
| Type: | Centerfire rifle |
| Designer: | Robert Whitley |
| Parent: | 6.5 Grendel |
| Case Type: | Rimless, bottleneck |
| Bullet: | .243 |
| Neck: | .271 |
| Shoulder: | .4323 |
| Base: | .4433 |
| Rim Dia: | .4449 |
| Rim Thick: | .0591 |
| Case Length: | 1.525 |
| Length: | 2.260 |
| Case Capacity: | 36 |
| Rifling: | 1-8" |
| Primer: | Small rifle |
| Bw1: | 105 |
| Btype1: | Berger VLD |
| Vel1: | 2750 |
| En1: | 1763 |
| Balsrc: | http://www.6mmbr.com/gunweek068.html |
The 6mm AR / 6x38mm AR is an intermediate centerfire wildcat cartridge initially designed by Robert Whitley[1] for long-range performance in an AR-15 rifle.
The cartridge uses a 6.5 Grendel case that has been necked-down to accept a 6.2 mm (.243 in) bullet.
The 6mm AR takes advantage of the wide variety of 6.2 mm (.243 in) caliber bullets. Slim, long bullets with high ballistic coefficient are ideal for energy retention at long ranges.[2]
It is similar to the 6PDK which also uses a 6.2 mm bullet and a similar muzzle energy and case capacity to the 6mm AR and 6.5 Grendel, in a casing somewhat popular[3] for the AR-15, a necked-down 6.8mm Remington SPC casing.
This variant uses an Ackley Improved fire formed case with less tapering and a 40-degree higher shoulder permitting a larger powder capacity. It is claimed by its maker to be capable of driving a or heavier grain projectile at (satisfying the "6mm Optimum").
These wildcats also push forward the shoulder of the same necked Grendel case similar to the Turbo 40, yielding more powder capacity. or heavier grain VLD boat-tail bullets have to be seated deeply within the case neck, however, rendering some of these volume gains illusory but there is an increase in volume even with the longer bullets nonetheless.
Similar to the 6mm Turbo 40 and 6mm FatRat, the 6mm Grinch has a blown-forward shoulder on par with the 6mm Dasher to eke maximum powder capacity from the necked Grendel case.