6mm AR

Not to be confused with 6mm ARC.

6mm AR
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 for long-range performance in an AR-15 rifle. It should not be confused with Hornady‘s 6mm ARC.

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.

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 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 to be capable of driving a 100+ grain projectile at 2900fps (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 eke 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.

See also

• 6mm Optimum
• List of rifle cartridges
• Glossary of firearms terminology
• .223 Remington