What Caliber Is An AR 15?

What Caliber Is An AR 15

The AR 15 is one of the most popular rifles on the market and it doesn’t take long for you to realize why. The thing is, with such popularity – it can often be a little confusing as to what ammunition and cartridges need to be used with it. 

Bizarrely, it’s one of a handful of rifles that has a standard but also a whole host of additional ammunition that you can use. Typically, you can expect .223/5.56mm Remmington but there’s way more than this. 

This article looks at all of the different cartridges and ammunition you could load your AR 15 with. So, read on to learn more!

204 Ruger 

With an average weight of around 35 grams, this cartridge was initially ready to fire rapid bullets at vermin and it can do that easily at over 4000 fps! 

Despite its relatively early age being introduced in 2004 by Hornaday – it seemingly has had its shelf life already. The popularity of this cartridge started strong but quickly dropped out of favor. 

In fact, you’ll be hard pressed to find rifles using this nowadays and that’s kind of a shame – considering this was one of the best with little recoil and an idyllic feel. 

22 Nosler 

This is really simple to convert from the original and intended use of the .223 Remmington, just get yourself a new barrel and 6.8 SPC mag. 

However, it is only Nosler where you can find the ammunition for this cartridge. Despite this though, it is certainly worth looking for – because it has over a quarter more powder capacity. 

What this means for you is a much pacier shot, regardless of the ammunition used, you’re looking at over 3000 fps. 

224 Valkyrie 

This is one of the more modern cartridges for the AR 15 and it allows you to use the AR 15 at a slightly longer range than you might have done before. 

The case is modified to the point where you can now use longer and more thin ballistic bullets. 

This is probably why it’s less surprising that this choice is becoming more and more popular. It’s much more tailored to your choices, and just gives you that little extra in the form of distance. 

25 – 45 Sharps 

One of the crowning achievements when it comes to cartridges, this is an improvement on the .223 Remington case but it has moved up to a .257 caliber. 

It was made with the sole purpose of big game hunting, and it certainly makes that a whole lot more simple! 

Despite this though, it doesn’t do well in terms of commercial sales with hardly any major manufacturer offering this type of ammunition required for it. 

However, if you do manage to pick it up somewhere – it’s ideal for varmint or big game hunting with very little recoil.

6.5 Grendel 

If you’re talking about cartridges that have moved away from the mainstream but hold a special place in some people’s hearts – here it is! 

Essentially a cult following product, since 2003 we’ve seen a rise in certain popularity but strangely not with most AR 15 fans – despite being incredibly multipurpose, with ammunition on offer with many manufacturers.

What Caliber Is An AR 15

6.8 SPC 

An early 2000s cartridge, this was likely made for military usage alone – despite that, it did have a lot of popularity until very recently. 

There is a good reason for that though. Unfortunately, this cannot take the same ammunition variety as the .224 valkyrie. 

300 Blackout 

This at one point in time was one of the most popular among its kind, especially with new shooters. 

This cartridge is ideal for subsonic and supersonic use and that makes it perfect for ammunition ready for hunting. 

30 Remington AR 

Crafted by Remington, this has been hailed as possibly the best cartridge ready for big game hunting… at least, that was the idea!

The problem that many enthusiasts will be aware of is that Remington made several errors with this cartridge and it was about the same time that the AR 15 popularity was spiraling throughout America. 

300 Hamr 

Now we’re going extremely modern with this 2018 model. Mirroring the capabilities to that of the .30 Winchester, this is ideal for big game hunting and of course, varmint hunting. 

One downside is that the suitable ammunition can only be found from one source, but if you’re okay with that – you’ll certainly be happy with this! 

350 Legend 

A fantastic creation from Winchester here, it has much more power than many on this list and as a result – forget big game hunting, it’s time to move onto hogs! 

It truly is a cartridge that is ready for all occasions and highly popular among modern hunters! 

450 Bushmaster 

Relatively modern but certainly powerful, with the capabilities of firing a 250 grain bullet at 2200 fps, you’ll find this cartridge slightly problematic with an AR 15. 

This is due to the high recoil and poor trajectory. However, despite this – for some reason, many still opt for this. 

Why Does The Caliber Matter?

It’s really all about the tasks you’re hoping to perform. For example, think about it like this – you wouldn’t use a tablespoon to cut a steak because it’s the wrong tool. 

This is precisely the same thing here. If you’re hoping for big game hunting, your AR 15 would be better off with the 6.5 Grendel (of course, this will depend on whether your state allows big game hunting or not!). 

Other than this, varmint hunting would probably warrant the .224 valkyrie. Whatever the case, the best thing to do is to speak with a firearms expert for much more in-depth advice, or speak with a hunter. 

Remember, when it comes to hunting – safety is paramount and you’ll want to be sure you have the correct equipment, tools and knowledge. 

The Bottom Line 

There’s plenty of cartridges available for the AR 15, so don’t feel confined to stock!

Matthew Osborn

Matt is an entrepreneur who has created and successfully exited multiple companies and brands. Now, he dedicates his time to Legionary, where he produces content on guns, family, and freedom.

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