6mm AR

6mm AR
6mm PPC.jpg
Type Centerfire rifle
Place of origin  United States
Production history
Designer Robert Whitley
Specifications
Parent case 6.5 Grendel
Case type Rimless, bottleneck
Bullet diameter .243 in (6.2 mm)
Neck diameter .271 in (6.9 mm)
Shoulder diameter .4323 in (10.98 mm)
Base diameter .4433 in (11.26 mm)
Rim diameter .4449 in (11.30 mm)
Rim thickness .0591 in (1.50 mm)
Case length 1.525 in (38.7 mm)
Overall length 2.260 in (57.4 mm)
Case capacity 36 gr H2O (2.3 cm3)
Rifling twist 1-8"
Primer type Small rifle
Ballistic performance
Bullet mass/type Velocity Energy
105 gr (7 g) Berger VLD 2,750 ft/s (840 m/s) 1,763 ft·lbf (2,390 J)
Source(s): http://www.6mmbr.com/gunweek068.html

The 6mm AR is a centerfire wildcat cartridge initially designed by Robert Whitley[1] for long-range performance in an AR-15 rifle.

Description

The cartridge uses a 6.5 Grendel case that has been necked-down to accept a 6 mm (.243 in.) bullet.

The 6mm AR takes advantage of the wide variety of .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 6mm 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.

6mm AR Turbo 40 Improved

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[4] to be capable of driving a 100+ grain projectile at 2900ftp (satisfying the "6mm Optimum").

6mm Rat and FatRat

These wildcats also push forward the shoulder of the same necked Grendel case similar to the Turbo 40, yielding more powder capacity. 100+ grain VLD boat-tail bullets have to be seated deeply within the case neck, however, rendering some of these volume gains illusory.

6mm Grinch

Similar to the Turbo 40 and FatRat, this has a blown-forward shoulder on par with the 6mm Dasher to eek maximum powder capacity from the necked Grendel case. In 2016, Greg King won a National Bench Rest Shooters Association event with a "Grinch" wildcat, besting a field of mainly 6mm PPC competitors.[5]

See also

References

  1. ↑ http://www.6mmbr.com/gunweek068.html
  2. ↑ http://6mmar.com/6mm_AR_Loading_Info.html
  3. ↑ ammoseek rankings:
  4. ↑ http://www.6mmar.com/6mmAR_Turbo_40_Improved.php Shooting the 6mmAR Turbo 40° Improved
  5. ↑ http://forum.accurateshooter.com/threads/6mm-grinch-defeats-entire-field-of-6ppcs.3912901/ 6MM GRINCH Defeats entire Field of 6PPCs


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