AR-15 Caliber Comparison Chart: Every Chambering Ranked

Last updated July 2026 · By Nick Hall, AR-15 shooter who has owned rifles in most chamberings on this chart

Last updated July 2026. This post contains affiliate links. If you click and buy, I may earn a small commission at no extra cost to you. Full disclosure.

Table of Contents

AR-15 platform chambers way more cartridges than most people realize. From .22 LR plinking rounds to .50 Beowulf thumpers, there’s a caliber for every purpose. But sorting through them all and figuring out which one actually makes sense for your use case is overwhelming without a clear comparison.

I’ve shot most of these calibers extensively and built dedicated uppers for several of them. Some are genuinely useful innovations. Others are solutions looking for a problem. Here’s the honest breakdown with data to back it up.

AR-15 Caliber Comparison Chart

This chart compares every common AR-15 chambering across the specifications that matter most. All velocity data is from 16″ barrels unless noted.

AR-15 remains the most popular rifle platform in America with over 24 million in civilian hands according to NSSF estimates.

Compatibility Quick Reference

Not all caliber conversions are created equal. Some only require a barrel swap. Others need a new bolt, magazine, or both. Here’s what you need to switch between calibers.

.223 Remington / 5.56 NATO

Standard. The one every other caliber is compared against. It’s cheap, widely available, soft-shooting, effective to 500+ yards, and suitable for everything from home defense to varmint hunting. If you’re buying one AR-15 caliber, this is it. No question.

Only real weakness of 5.56 is terminal performance on larger game (deer-sized and up) at extended ranges, and energy delivery beyond 500 yards. For those roles, bigger calibers shine. But for 90% of what most people use an AR-15 for, 5.56 is the answer. For the difference between .223 and 5.56, see our complete comparison.

Shop 5.56 / .223 Ammo Deals →

.300 Blackout

300 BLK was designed to do one thing incredibly well: run suppressed from short barrels. It uses the same bolt face and magazines as 5.56, so converting is just a barrel swap. Supersonic loads (110-125gr) are effective for self-defense and hunting. Subsonic loads (190-220gr) through a suppressor are movie-quiet and devastating at close range.

Downside is cost ($0.70-1.50/round) and limited effective range (300 yards for supersonic, 100 yards for subsonic). It’s not a replacement for 5.56 as a general-purpose round. It’s a specialist. And it’s the absolute best at its specialty. See our best 300 Blackout rifles guide for top picks.

Critical safety note: .300 BLK rounds will chamber in a 5.56 barrel but will cause a catastrophic failure when fired. If you own both calibers, label everything clearly and never mix ammunition. This has caused real injuries and destroyed rifles.

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6.5 Grendel

6.5 Grendel is the long-range king of the AR-15 platform. It fires heavy, high-BC bullets that retain energy and resist wind far better than 5.56. At 600+ yards, the Grendel is carrying more energy than 5.56 has at 300 yards. It’s a genuinely impressive cartridge for precision work and hunting.

Trade-off is reduced magazine capacity (about 24 rounds in a standard-length body), the need for a dedicated bolt and magazine, and higher ammo cost. It’s also a bit more finicky about barrel quality and ammo selection than 5.56. But when you want to reach out past 500 yards from an AR-15, nothing on the platform competes with Grendel. See our 6.5 Grendel guide for more.

6.8 SPC (6.8 Remington SPC)

The 6.8 SPC was developed by the US Army Marksmanship Unit and Remington as a replacement for 5.56 with better terminal performance. It hits harder than 5.56 inside 300 yards and is an excellent hunting round for deer-sized game. The military ultimately didn’t adopt it, but it found a loyal following among hunters and tactical shooters.

In 2026, the 6.8 SPC is somewhat overshadowed by the 6.5 Grendel (which shoots further) and .300 Blackout (which suppresses better). Ammo availability and selection have decreased. If you already have one, it’s still excellent. If you’re building new, I’d lean toward Grendel or Blackout depending on your needs.

.224 Valkyrie

Federal designed the .224 Valkyrie to push the AR-15 past 1,000 yards using heavy, high-BC .22 caliber bullets (75-90gr). It’s based on the 6.8 SPC case necked down to .224. With the 90gr Sierra MatchKing, it stays supersonic past 1,300 yards from a 24″ barrel.

Early ammo quality issues and limited barrel options hurt the Valkyrie’s reputation. The situation has improved, but it remains a niche cartridge. If extreme long-range from an AR-15 is your goal and you’re willing to handload, Valkyrie is interesting. For most shooters, 6.5 Grendel is more practical and better supported.

Shop .224 Valkyrie Ammo →

.350 Legend

Winchester’s .350 Legend was designed specifically for states that require straight-wall cartridges for deer hunting (Michigan, Ohio, Indiana, Iowa, and others). It’s a mild-recoiling, effective deer cartridge that works in a standard AR-15 with just a barrel swap and dedicated magazine.

Effective range is limited to about 200 yards, and it drops significantly past 150. But within that range, it’s a capable deer cartridge that’s pleasant to shoot. If you hunt in a straight-wall-only state and want to use your AR-15, the .350 Legend makes a lot of sense. Outside of that specific use case, 5.56 or 6.5 Grendel are better all-around choices. Check our AR-15 hunting guide for more.

Shop .350 Legend Ammo →

.450 Bushmaster

The .450 Bushmaster is a big-bore thumper that pushes 250-300gr bullets at rifle velocities. It hits like a freight train inside 200 yards and is legal in straight-wall cartridge states. Recoil is significant but manageable in the AR-15 platform.

It requires a dedicated bolt, barrel, and single-stack magazines (about 7 rounds). Ammo is expensive ($1.50-2.50/round) and selection is limited. But for big game hunting (black bear, elk at close range, hogs) from an AR-15, few cartridges hit harder. It’s also popular in states like Michigan where straight-wall cartridges are required for rifle deer hunting.

Shop .450 Bushmaster Ammo →

.458 SOCOM

The .458 SOCOM was developed for close-range stopping power, reportedly after the Battle of Mogadishu showed 5.56’s limitations against determined attackers. It fires heavy .458 caliber bullets (250-600gr) from a standard AR-15 lower with a dedicated upper.

Subsonic .458 SOCOM through a suppressor is an experience. You’re launching a 500gr+ projectile at subsonic velocity with very little sound. The energy transfer is devastating at close range. It’s a specialty tool, but it’s a cool one. Ammo is expensive, availability is limited, and the cartridge is best suited to handloaders who can optimize loads.

Shop .458 SOCOM Ammo →

.50 Beowulf

Alexander Arms’ .50 Beowulf is the biggest bore you can run in an AR-15 lower. It fires .50 caliber (.500″) bullets from 300-400gr at around 1,800 FPS. The energy is tremendous at close range, making it popular for hog hunting and vehicle-stopping applications.

Recoil is stout but not punishing in the AR-15’s buffer system. Magazine capacity drops to about 7 rounds in a standard-length body. Ammo costs $2-3 per round and selection is limited. Like .458 SOCOM, this is a niche cartridge for enthusiasts and specialized applications.

Shop .50 Beowulf Ammo →

6mm ARC

The 6mm ARC (Advanced Rifle Cartridge) is the newest chambering worth building around, and in 2026 it has become the go-to long-range option on the standard AR-15 platform. Hornady designed it to deliver 6.5 Grendel-plus ballistics from the same small frame, pushing 108-grain match bullets around 2,750 FPS with a high ballistic coefficient that stays supersonic past 1,000 yards. It runs 6.5 Grendel-pattern magazines and bolts, so converting an existing lower is a barrel-and-bolt swap.

For precision shooting, coyote-to-deer hunting, and anyone who wants true long-range capability without moving up to an AR-10, the 6mm ARC is the most interesting modern chambering on this list. Ammo runs about $1.25 to $1.75 per round and factory and component support has grown fast. If you are building a dedicated long-range AR-15 today, this is the caliber to look at first.

.22 LR Conversion

A .22 LR conversion kit (like the CMMG conversion or Dedicated .22 LR upper) turns your AR-15 into a .22 trainer for about $200. At $0.05-0.10 per round, you can shoot all day for the cost of a couple boxes of 5.56. It’s the best training investment you can make.

Drop-in conversion kits replace the bolt carrier group and use a dedicated .22 LR magazine. They work in your existing 5.56 barrel and function reasonably well, though accuracy is only minute-of-soda-can at 50 yards. Dedicated .22 LR uppers with proper .22 barrels are more accurate but cost more. Either way, the ability to practice trigger control and fundamentals for pennies per shot is invaluable.

Which Caliber Should You Choose?

• General purpose, first AR: .223/5.56 (no contest)
• Suppressed SBR: .300 Blackout
• Long-range precision: 6.5 Grendel
• Deer hunting (straight-wall states): .350 Legend or .450 Bushmaster
• Home defense: .223/5.56 (see our HD guide)
• Big game hunting: .450 Bushmaster or .458 SOCOM
• Training on a budget: .22 LR conversion
• 1,000-yard precision: .224 Valkyrie or 6.5 Grendel

For the deep dive on choosing your ideal caliber, check our best AR-15 caliber guide. And for rifle recommendations in each chambering, our best AR-15 rifles roundup covers options across multiple calibers.

Browse All AR-15 Parts & Ammo →

Frequently Asked Questions