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AR-15 Calibers Overview [Which is Best For You?]

AR-15 Calibers Overview [Which is Best For You?]
December 20, 2021 Edited March 23, 2023 32978 view(s)
AR-15 Calibers Overview [Which is Best For You?]

What a lot of people really don’t know is that the AR-15 is truly one of the most versatile platforms ever designed. Normally chambered in one of three or four cartridges, it can actually handle dozens more.

Here is a pretty long list of some awesome options that you may not know are even available.

Some of these are awesome, some of these are standard, all of them are interesting!


Most, But Not All

Before we get to the list I want to throw a little disclaimer in here. Yes, I know this is not every single cartridge that you can find for the AR-15.

Some of these are basically extinct, some of these are super common, and there are a dozen or more others that didn’t make it on our list.

Most of the ones we’ve left off are wildcats, some of them are just very minorly modified versions of something that is on the list, some of them are just so unobtanium and uninteresting that I didn’t feel like doing the jazz hands on my keyboard to talk about them.

If your favorite cartridge you’ve ever shot isn’t on the list, tell me about it in the comments! Just please don’t get mad that we didn’t include it.

Make a good enough case as to why it should be included and maybe we’ll add it in ;)


AR-15 Rifle Cartridges

General Purpose / Multi-Role

223 Remington / 5.56 NATO

If you don’t know much about the AR-15, you should at least know that .223 Remington/5.56 NATO is the OG standard for the platform.

It’s actually pretty rare to find an AR-15 actually chambered for just .223 Remington these days, most are chambered for 5.56 NATO or 223 Wylde and can fire .223 Rem and 5.56 NATO ammo just fine.

This is a great do-all option that does well in everything from home defense to hunting game.

While this would never be my first pick for something like deer, it can be used for deer -- if it’s legal in your state.

What 5.56 really shines in are roles that are more people-related. Be it competition, training, or personal defense.

[Shop 5.56 uppers and more from Bear Creek Arsenal!]

5.56 and 223 bullets



The classic AK-47 cartridge has been adopted to the AR-15 more because we can than anything else.

Historically, 7.62x39 really didn’t work that well in the AR-15. Bolts were a lot less durable, feeding and ejection issues were common, and the magazines were weird at best.

Because of those issues and the fact that 7.62x39 was so perfect in an AK, AR-47s as they were often called got a bad reputation.

That was the past though.

Bear Creek Arsenal has made a number of design changes and enhancements like an improved bolt, enhanced firing pin, and better magazines that have pushed the AR-47 forward in a huge way.

These days, with the right setup, 7.62x39 can run outstandingly well in an AR -- both brass- and steel-cased ammo!

[Shop 7.62x39 uppers and more from Bear Creek Arsenal]

7.62x39 ammo


.22 Long Rifle

A lot of people look down on the humble .22 LR but it has a deserving place in everyone’s armory.

For the AR-15 .22 LR is really handy and fun. From training new shooters to hunting small game, .22 LR has a long list of uses and it does all of them at a much cheaper price than any other AR-15 cartridge can.

Personally, I love to use .22 LR uppers for training. Firearm manipulation and close distances shooting are both great ways to use .22 LR to train while keeping your budget a lot smaller than if you used 5.56 NATO.

For a lot more info and some recommendations, take a look at our Complete Guide To The AR-22!

.22 LR Ammo


Hunting Large Game

.350 Legend

Most states don’t care what shape your rifle cartridge is in, but there are a few that do. Why? Probably the same reason California thinks a flash hider makes the rifle more spooky.

For those odd duck states that believe deer should only be harvested with straight wall cartridges, the .350 Legend was created.

Ballistics closely match 300 Blackout making this basically a sub-250 yards deer puncher.

It isn’t cheap, there isn’t a lot of ammo for it, and outside of those weird law states -- there isn’t a real need for this round to exist.

But for those that need it, nothing else will do.

[Check out our 350 Legend guide for more information about the caliber.]

350 Legend Ammo


.450 Bushmaster

Designed for big game, .450 Bushmaster puts 12ga slug power in an AR platform. Bourn out of Jeff Cooper’s mind, this big honker of a cartridge is great for putting down any sized animal in North America.

Just make sure to get fairly close because this has the ballistics of a lead rainbow.

You’ll get loads of power upfront, but it drops faster than an Astro’s OPS without the trashcans.

[Check out our guide to 450 Bushmaster ballistics here!]

450 Bushmaster ammo


.458 SOCOM

Maybe the coolest origin story of any AR-15 cartridge, the .458 SOCOM was designed because of veterans of Operation Gothic Serpent telling firearms developers that there needed to be an AR-15 cartridge with more power.

Something they don’t tell you in the movie Black Hawk Down is that many of the hostile forces that Delta Force and the Rangers faced in Somalia used a local drug called Khat, basically, a stimulant that helped them ignore pain and wounds.

Ballistics are almost the same between .458 SOCOM, 50 Beowulf, and .450 Bushmaster -- but .458 SOCOM has the benefit of being designed with the intent of as little changes to the standard M4 as possible.

A new 458 SOCOM upper and you’re good to go. [See our article comparing 458 SOCOM vs 50 Beowulf here!]

458 SOCOM ammo


.50 Beowulf

Designed by the legendary Bill Alexander of Alexander Arms, .50 Beowulf / 12.7x42 is yet another thumper cartridge designed to give you a lot of power at short ranges.

While ballistics really aren’t any difference between the big three thumpers, if you want a true 50 cal -- this is the one to get.

[See our complete guide to 50 Beowulf here!]

50 Beowulf ammo


.300 Blackout

Built for suppressor use and to mimic the ballistics of 7.62x39 while being far more reliable and durable in an AR-15, .300 Blackout is great for things like wild boar.

Because it was designed for short barrels and suppressors, this is perfect for barrels as short as 9-inches. And since subsonic rounds are limited on speed, even in a 9” barrel they give you the same performance.

If you need more punch, load up the supersonics and go to town. [Read our complete guide to 300 Blackout here!]

300 Blackout ammo


.300 Ham’r

Introduced a few years ago by Wilson Combat, the .300 Ham’r is actually a pretty reasonable and capable cartridge.

Effectively having the same ballistics as .30-30 (135gr at 2,400 with a 16” barrel) this is a cool addition to the AR-15 lineup.

Sadly, it really isn’t popular… and there is a good reason. Wilson Combat is keeping the cartridge exclusive and proprietary. They are the sole source of parts, uppers, rifles, and ammo.

300 Ham'r


Hunting Small Game / Varmits

.25-45 Sharps

While some states ban bottle-neck cartridges for big game, still others ban anything at or under .224 caliber.

The .25-45 Sharps set out to make the AR-15 legally viable as a hunting rifle in all states that allowed bottle-neck cartridges by introducing a .25 cal bullet.

Ballistics are solid and are perfectly reasonable for both big game like deer and smaller varments, depending on the bullet you pick.

But this just never caught on. No major brand offers ammo for it and finding a barrel for it is basically impossible.

Using a .223 Remington case that is just opened up to .25 cal, this is very easy to handload if you’re willing to do it.

25-45 Sharps Ammo


.22 Nosler

Based on the 6.8 SPC but necked down to .224, the .22 Nosler sends a 55gr bullet at a screaming 3,300 FPS.

And since it uses the same bolt as a normal AR-15, just switching the barrel and using 6.8 SPC magazines makes this a very easy conversion.

But the bad news is that Nosler is the only one offering ammo for it. Their ammo is awesome, but one source isn’t great.

22 Nosler Ammo


.204 Ruger

An outstanding varmint cartridge, this little guy sends a 32gr bullet at well over 4,000 FPS.

But as you may have guessed, ammo and complete rifles are hard to find. That said, barrels aren’t totally unseen in the wild and building your own upper is pretty easy.

Load up some barrel burners and you can lay out dozens of little critters with ease.

204 Ruger Ammo


Long Range

.224 Valkyrie

Valkyrie was one of the first “long range” cartridges I ever got into and I really liked it… when it worked.

Sadly, this cartridge was over-promised and under-delivered. While its long range ballistics are very good, there were a number of design issues when it first came out that took time for the community to resolve.

While I ditched it back then after it not performing up to my expectations, the cartridge has found it’s legs and is making a comeback.

Get yourself the right twist and some good loads and you can reach out very far with this little guy.

Plus, it has one of the best names. And yes, that counts.

224 Valkyrie Ammo


6.5 Grendel

One of my favorite cartridges, the 6.5 Grendel comes from the mind of Bill Alexander (same guy that made the 50 Beowulf) and is one of the greatest all-round AR-15 cartridges ever made.

Supersonic past 1,000 yards, delivering 1,000 ft.lbf out to at least 400 yards, and still fits 25 rounds in a standard 30-round 5.56 NATO magazine size, Grendel can do a lot of things and do them well.

About the only thing I wouldn’t recommend it for would be really big game, like elk+. Anything else in North America, Grendel can handle it.

It’s also just a really fun round to take long range. Shooting an AR to 1,000+ yards isn’t easy but it is a lot of fun!

[Read our Guide to 6.5 Grendel and find 6.5 Grendel uppers from Bear Creek Arsenal!]

6.5 Grendel Ammo


6.8 SPC

Designed in the early 00s in a joint venture between Remington and the Army Marksmanship Unit, this was intended to possibly replace the 5.56 NATO for the US armed forces.

You might have guessed though, it didn’t. While it saw combat overseas with some special forces units (and some claim are still in their inventory to this day) and proved popular with those that put it to the test, it simply didn’t catch on.

Even when something is better than what the military currently uses, sometimes it just isn’t better enough.

Today, the 6.8 SPC is a bit overshadowed by things like 6.5 Grendel, 6mm ARC, and even .224 Valkyrie.

6.8 SPC is good, but might be a second runner-up at best.

6.8 SPC ammo


6mm ARC

There isn’t much info out about the history of this brand-new cartridge, but what we do know is pretty cool.

Developed by Hornady while working with the DOD, this was designed for an unknown group or agency within the DOD for use in unknown places doing unknown things.

I’m not being cryptic, that is literally all the press release said.

Basically, someone in the DOD wanted a rifle cartridge for the standard AR-15 (or more likely something like the Mk12) that could reach out a lot further with more punch than what 5.56 can do, even the super customized 5.56 that is in use with things like the Mk12.

What Hornady came up with was a 6mm AR-15 cartridge that can sling a 103-grain ELD-X bullet at 2,800 FPS.

That’s pretty darn good for an AR-15. It basically makes it like 6.5 Grendel that ate its spinach.

6mm ARC


Parting Shots

That’s a big list, I hope at least a few of them were ones you’ve never heard of!

[As you can see, one of the best things about the AR-15 platform is that all of these calibers (and more) can be fired from a mil-spec AR-15 lower. To add one of these calibers to your arsenal take a look through our AR-15 uppers. These complete upper assemblies come with everything you need to start shooting out of the box including a bolt carrier group and charging handle.]

If your #1 fav cartridge didn’t make the list, let us know in the comments!

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Alex Brill
December 21, 2021
.22 nosler is not 6.8spc necked down. That is what .224 Valkyrie is.
Paul k
January 20, 2022
I would also like to see 6mm arc
John Rakoci
December 26, 2021
I have many BCA products and will no longer buy an upper from any other company 7 62 X 39 is one of my favorite calibers and I do send a lot of lead down range I own 2 BCA uppers in 7 62 and have a spare BCG BCA is in the lead with this caliber in an AR but still there is a weak point, the extractor Is the extractor metal too hard? I never take a 7 62 to the range without a spare bolt from one of the other BCGs I own but I still enjoy these rifles a lot!
Beachley Main
December 28, 2021
Have you all ever thought about doing a 17 WSM upper? I love the 6.5 Grendel you sold me, but looking for something for rabbits (already have a few 22LR riffles)
December 29, 2021
We are not at this time.
January 19, 2022
You really should consider the 17 WSM, if you do I will buy 2, based on barrel length. I know this won’t financially change your business arc but it would change my fun arc!
Solomon Dudley
January 9, 2022
Hey Bear creek my Solomon dudley bring a new calibers back 338 federal 224 and 30 30 win in ar 15 style rifle but make sure the head space is right I have not seen any other companies making these calibers oh.224 they but other than that nothing something to.think about for 2022
Tom Drew
January 10, 2022
Are you going to offer a 6mm arc anytime soon?
January 10, 2022
We do not have any plans at this moment make sure you sign up for our newsletter ( to stay up-to-date.
January 12, 2022
in southern michigan, we have a choice, either use a shotgun, or a straight wall pistol cartridge. the only candidates are .357 Max, .350 legend or .450 BM. i personally prefer the 35s. more and more, i hear of fellow hunters choosing the .350L. i have a max and 350L in T/C encore, and i am building a 350L based on a BCA barrel. just waiting for some parts at this time.
Michael Kirk
January 12, 2022
50 BMG upper... you would sell more than anyone!...Most all of the other companies are months or years lead time.
Mister McCool
February 4, 2022
(His will be done)
Wayne Chapman
April 13, 2022
Would really like to see Bear Creek come out with a 358 Winchester upper would be good out to 300 yards and would be a hell of a thumper
Patrick Robare
June 15, 2022
You should build a 325wsm upper for an ar10 platform
Reed Gregory
June 21, 2022
They won’t make a magnum AR-10, it takes oversize bolt head longer magnum length gas tubes and adjustable gas blocks and they are very hard on extractors, and open up the ejection port, their ain’t but a few that play with these calibers, dpms made some in 300 saum but had lots of ejector problems
H Farler
June 17, 2022
I live in one of the odd ball states [ straight wall only for deer] i didn't realize how popular your 350 legend parts were until i tried to build one, have my barrel on back order now
Wayne Cashman
June 18, 2022
I am completely in love , I ran 120 rounds through my new 300 blackout upper from Bear Creek arsenal, simply fantastic, I ran 125 gr and 220 subsonic , extremely pleased with the performance and acaccuracy. I am a customer forever ,
richard simms
June 20, 2022
i bought one of your 22mag uppers a couple of months ago. very accurate and has cycled flawelessly so far. other than paying 50 bucks more for it than your selling it for now... good job n keep it up!]
June 20, 2022
How about some really interesting cartridges for the AR 15:: 351 WSL 357 Automag 357- 475 Wildey 357- 45 Win. Mag. 400 Corbon 401 WSL 10 mm Magnum 41 Automag 41- 475 Wildey 41- 45 Win. mag. 429 DE 44 Automag 45 Win. Mag. 45-475 Wildey 475 Wildey 50 Action Any of these would be great in a AR15 for hunting hogs, coyotes and deer, and for home protection.
Brian Strohofer
June 23, 2022
No ammo for any of those unless you hand load. I'm all about wildcats but i understand it's a losing proposition in a business perspective unless you're a barrel maker and even then you may not sell many
Calvin heath
June 22, 2022
6.8 spc would be nice 16 or 18 inch 1/ 11 twist. I lost one in a divorce it was a tack driver ever thing i own is a tack driver. You just have to know how to shoot. An have good product's bca. Is really good thanks guy's
John Kreuz
June 26, 2022
Not sure how this would work in AR platform? 45-70 would be awesome!
Hud Reese
August 27, 2023
That would be awesome if you could physically fit that cartridge through the mag well of a ar15. Also rimed cartridges are next to impossible to get to feed stacked in a box magazine. If it were possible I would definitely get one.
Gregory Walker
June 28, 2022
I currently own five of your uppers in a variety of calibers and they all perform great. My favorite is the 450 Bushmaster. It puts hogs down instantly. For varmints I wish you would consider making an upper in 17 WSM. I have 2 savage rifles chambered in the 17WSM. I have killed a pile of coyotes and smaller varmints. The 17WSM is a fairly new cartridge that is gaining in popularity. It's a 3000 fps rimfire and would make an awesome AR 15 caliber. If you would make an upper count me in for the first one!
Jason Martin
June 29, 2022
6.5 grendel vs 6.8spc?? Or where the f##$ is all the grendel ammo??I jumped on the 6.8spc bandwagon when panther arms had a ar15 line designed with hunting in mind, great idea...but after all my grandkids have had deer&hogs get up & run away from a well placed shot- so the pretty 6.8spc sits in gun safe hell& all my kids,grandkids wonder where the hell all the grendel ammo has gone??Texas??? They sure as hell don't need any there!!,meanwhile piggies are everywhere in NW Florida & no Good, grendel ammo to be had!! It's been 3years since I could even buy a box of wolf ammo for 6.5 grendel-wtf???,Capt J
July 4, 2022
Ammoseek has you covered.
Brian Cross
July 1, 2022
You all at Baer Creek thought of a 22 hornet AR upper ? I think that would be a head turner !!!!
July 2, 2022
Hey , completely off topic but that buffer less 9mm is that going to be available for sale as an upper only or will you have to purchase the whole rifle?
July 5, 2022
The 9mm bufferless will be available as full rifles and Complete Upper assemblies on release.
Jimmy Hardin
July 8, 2022
22 hornet is a great little cartridge It would be awesome on an AR 15 platform. I had a savage over and under 22 hornet with 20 guage lower It was great for javelnas out to about 100 yards with head shots
Jimmy Hardin
July 4, 2022
What are the odds of an 8mm Mauser cartridge coming to Bear Creek with about a 140 grain bullet
Hud Reese
August 27, 2023
The odds aren't great. 8mm Mauser has to large of dimensions to fit ar15 platform
July 4, 2022
Would like to see a 545x39 upper
Gregory Dewees
July 5, 2022
Have an AR15 .350 Legend build with a BCA barrel. Tickled inside and out about it!
ED Grisham
July 7, 2022
Would love to see a 17HMR upper.. also something bigger than 308 for the 10... 300 Win mag or maybe the short mag?
July 9, 2022
I got onto 350 Legend after developing the 400AR wildcat and getting tired of paying for .400 bullets out of black powder sabots. Plus necking-up and cutting down Carcano brass got tedious, not to mention recoil taking a toll on my old bones. So I justified getting a 20" BCA 350 Legend upper to carry on some of my 400AR experiments without the cost and the kick. And I'm really liking it. Instead of a 7.62x39 bolt as with the 400AR, it uses a standard .223/5.56 bolt, but the big bonus is it has industry-wide support with brass, bullets, reloading dies and magazines. I believe the cartridge has a future not only because it looks just like a baby 400AR, but because it can use common 9mm pistol bullets, which during these tight ammo times has kept me in plinking fodder.
July 31, 2022
6mm ARC is getting a lot of Hornady Hype Sponsored Youtubers are over inflating its capabilities in an effort to sell the new unicorn. a 103 grain ELDx 2800 fps in a 24 inch barrel. But your not getting those numbers in shorter barrels. In fact you hear a lot of talk but what is 95 grain barnes lrx getting in a 16.5 inch barrel in a 6mm ARC? I know a 6,8 SPC performs excellect in a short barrel from a 16.5 inches, 2750 FPS, 95gr Barnes ttsx. That set up is anchoring wild Boar in Texas!
December 1, 2023
How about the new 400 legend by Winchester, l have a 350 legend and love it
David Ewing
April 4, 2024
I have eight builds using bear creek for hunting hogs,Deer and small game on the farm. I’m completely satisfied on how these products perform. Excellent product at a fair price point. Would love one in 44 magnum if it’s possible. Ruger made a 44 magnum semi automatic years ago. My son-in-law uses one hog hunting an excellent round on hogs and ammo is readily available. Just a thought. Reloading this round is cheap also. My 450BM is a hog hammer as well. Thanks for great products made Right here in the south.
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