LJ Bonham is a semi-subsistence hunter, hunting magazine editor, and firearms enthusiast who lives in the Rocky Mountains.
AR platform rifles are now the most popular rifle in America with well over five million owned nationwide. They are the fastest selling, fastest growing, segment in the firearms market today. The AR is a superb hunting rifle: accurate, reliable, and versatile. Today’s AR’s are available in more good hunting calibers than ever before. These cartridges are divided into two categories: those which fit into 5.56mm NATO-sized lower receivers and those for 7.62mm NATO receivers. Here’s an overview.
Cartridges for 5.56mm Receivers
This is the most common AR receiver size. The 5.56x45mm is a very short cartridge (2.26 inches) and it presents a significant challenge to design hunting cartridges which fit into its compact dimensions. Here are the best hunting cartridges for this platform
Civilian counterpart to the military’s 5.56mm NATO cartridge, the .223 is perhaps the premier varmint round. It shoots flat and is effective to 300 yards on coyotes, foxes, etc. It is available in 55 and 62 grain full metal jacketed bullets which cause minimal damage to valuable pelts.
In the last decade, bullet makers have introduced projectiles which take the .223 to a new level. Premium bullets such as Nosler’s Partition, Swift’s Scirocco, or Barnes’ TSX can humanly take medium-sized game under certain conditions. All the experts consulted by the author recommend precise shots at less than 150 yards in the heart, lungs, or central nervous system with the animal broadside to the hunter. The .223 is not recommended for long range hunting or for animals over 150 pounds.
Hunters are advised to use no less than 20 inch long barrels, with 24 inches preferred. Some states prohibit the .223 for big game hunting, so hunters should check applicable regulations with their local game department.
Here are some Federal factory .223 performance figures.
- 55 grain: 3240 fps/1282 ft-lbs
- 60 grain: 3160 fps/1330 ft-lbs
- 64 grain: 3050 fps/1322 ft-lbs
The wars in Iraq and Afghanistan generated complaints from frontline troops about the 5.56mm NATO (.223 Rem). They claimed it did not drop enemy combatants, who often took meth-amphetamine and other drugs, with sufficient authority, particularly at long range. Numerous ammunition companies and inventors labored to produce a cartridge which fit within the AR platform but hit harder than the 5.56. One such cartridge is the 6.5 Grendel.
The Grendel operates in standard AR magazines but throws heavier, wider bullets farther and with more energy than the 5.56. The Grendel delivers .30-30-like performance from a modern sporting rifle.
The Grendel can fire 125 grain bullets (twice as heavy as 5.56mm bullets) at close to 2500 fps. Few ammunition companies offer loads for the Grendel, so hunters should consider hand loading their own.
Factory ammunition performance:
- 123 grain: 2580 fps/1818 ft-lbs (Hornady)
The 6.5 Grendel is an excellent deer cartridge when used at reasonable range and with a premium bullet
6.8 Remington SPC
Remington responded to requests from the U.S. Military for a round which filled the gap between the 5.56 and 7.62 NATO cartridges. Their 6.8 SPC is the result. 6.8mm bullets are .277 caliber which, thanks to the popular .270 Winchester, gives hunters a wide choice in bullets.
Here are two typical deer loads from Federal.
- 90 grain: 2850 fps/1623 ft-lbs
- 115 grain: 2470 fps/1558 ft-lbs
.300 AAC Blackout
Developed by Advanced Armament Corp. in 2011, the .300 AAC is intended for use in suppressed firearms, first and foremost. As a result, there are several loads on the market with heavy (200 or 220 grain) bullets which travel at subsonic velocities to reduce the round’s audio signature. For best results, hunters should only use those loads on medium-sized game inside 50 yards.
The .300 AAC’s overall performance is similar to the Soviet designed 7.62x39mm cartridge used in the AK-47. Ammunition makers do not offer a wide selection in hunting loads for this caliber.
Here are the numbers for Winchester’s only Blackout high velocity load.
- 150 grain: 1900 fps/1202 ft-lbs.
This cartridge is the ubiquitous AK’s original chambering. Performance is equivalent to the .300 AAC, and hunting ammunition is available from many European and Asian manufacturers. American ammo companies have also begun to offer good hunting loads as well.
Performance is as follows.
- 123 grain: 2300 fps/1445 ft-lbs (Federal)
AR rifle manufacturer Bushmaster wanted to offer a true big game cartridge which fit into a standard 5.56-sized receiver. They collaborated with Hornady to develop it based on work done by Tom LeGendre. Hornady offers loaded ammunition and reloading components, and Remington makes ammunition as well.
Several companies offer conversion kits which allow an AR owner to change their mild 5.56 rifle into Thor’s hammer by just swapping the upper receiver, which takes less than ten minutes. The .450 Bushmaster uses standard AR-15 magazines.
The .450’s performance is close to modern .45-70 Government loads. Inside 100 yards it is suitable for moose, and bear; out to 200 yards it will take deer, antelope, and elk.
Here’s one load from Hornady.
- 250 grain: 2200 fps/2686 ft-lbs
Cartridges for 7.62mm Receivers
The larger AR-10 receiver is designed for the 7.62mm NATO (.308 Winchester); it will accommodate any cartridge based on the .308’s case. This opens a broad horizon for hunters since they can chamber their large frame AR for many excellent hunting cartridges. Here are some good choices.
The .260 is a .308 case necked down for 6.5mm (.264 inch) bullets. It duplicates the excellent 6.5x55mm Swedish’s ballistics but in a shorter, more efficient case. The .260 has several good points: moderate recoil, flat trajectory, and deep penetration. Used at appropriate ranges, the .260 will take anything from ground hogs to moose.
Here are a few typical Federal factory loads.
- 120 grain: 2950 fps/2319 ft-lbs
- 140 grain: 2700 fps/2266 ft-lbs
Like its smaller brother the .260, the 7mm-08 is a necked down .308 which uses 7mm (.284 inch) bullets. The 7mm-08 duplicates the legendary 7x57mm Mauser’s ballistics. Again, when used inside its performance envelope, it will take any thin skinned, non-dangerous game on Earth.
Federal factory performance is as follows.
- 120 grain: 3000 fps/2398 ft-lbs
- 140 grain: 2800 fps/2437 ft-lbs
- 150 grain: 2650 fps/2339 ft-lbs
Eugene Stoner designed the original Armalite AR-10 for the 7.62 NATO cartridge. This is a true big game round, suitable for deer out to 500 yards, elk to 250, and bear to 150. Most .308 AR’s work best with bullet weights between 150 and 175 grains, but some individual rifles perform well with 180 grains. Hunters should consult their rifle’s manufacturer for load recommendations.
Best performance comes from premium bullets. Hunters with short barreled carbines should consider bullets which expand well at reduced velocities such as the Nosler Partition or Sierra Game King.
Another advantage to the .308 is many ammo companies offer inexpensive 150 grain full metal jacket rounds which are perfect for wolf hunters who don’t want to damage the hide.
The .308 Winchester is now the most popular big game cartridge in America, due in no small part to the many AR’s which are chambered for it. Ammunition is plentiful, varied, and affordable.
Federal factory ammo performance:
- 150 grain: 2820 fps/2648 ft-lbs
- 165 grain: 2700 fps/2671 ft-lbs
- 180 grain: 2600 fps/2702 ft-lbs
Introduced in 2006, the .338 Federal is a .308 case necked up to .338 caliber. Inside 250 yards with heavy bullets, the .338 is suitable for large, heavy game such as moose or bear. With lighter bullets, it is great for deer out to 350 yards. Several companies offer AR’s chambered for this powerful cartridge.
A few Federal loads:
- 185 grain: 2680 fps/2950 ft-lbs (medium game only)
- 200 grain: 2700 fps/3237 ft-lbs
- 210 grain: 2630 fps/3225 ft-lbs
The .358 (.308 necked up to .35 caliber) has been a favorite in Alaska for moose and bear for decades. An AR chambered for this heavy hitter is a match for anything which walks in North America and elsewhere. Unfortunately, few companies make ammunition for this great cartridge, so hunters will have to hand load in most cases.
Here are two loads from Double Tap for the .358.
- 200 grain: 2675 fps/3178 ft-lbs
- 250 grain: 2425 fps/3264 ft-lbs
With all the superb cartridges available for AR platform rifles, hunters have no more excuses to not join the 21st century. The future belongs to the AR.
AR-10 Meets Moose, Film at 11:00
This content is accurate and true to the best of the author’s knowledge and is not meant to substitute for formal and individualized advice from a qualified professional.
Questions & Answers
Question: What do you think of a 6.5 Creedmoor for an AR?
Answer: Although I left it out, either Creedmoor (6mm or 6.5) would do well in an AR.
Question: Why wasn't the 204, 20 or the 223 WSM practical included in best-hunting cartridges for AR style rifles?
Answer: The article featured only production cartridges, not wildcats. In the .223 WSM's case, it's just not popular enough to interest a general audience, which was the piece's target demographic. Perhaps I'll include some, or all, of those in a second odd-ball and forgotten cartridges article some day.
Question: What do you think of the .458 SoCom rifle?
Answer: That's a good one, too. It is a good pick for boar (hog) and bear.
Question: What do you think about the Beowulf .50 caliber?
Answer: It's a good round. The article focused on the most popular AR cartridges and left out many fine boutique rounds, such as the Beowulf, due to space limitations.
© 2017 LJ Bonham