Big bullets, big cartridges, and shmedium rifles.
Taking big game is one of the few areas that a standard AR-15 doesn’t do well in, but combine an AR with 450 Bushmaster and you have a whole new ballgame.
How does it stack up to a legendary classic like .308 Winchester? We got that info, ballistics, recommendations, and a lot more!
Sure, But Why
To a lot of you, this comparison might seem kind of… odd. I mean, even someone casually familiar with these two calibers can likely tell that these are not similar.
The answer is simple: A lot of readers are interested in this exact comparison. I don’t know why, but who am I to judge.
Y’all asked for it, so you get it.
Holla in the comments with more suggestions of what we should cover!
Story Behind The Cartridges
450 Bushmaster
Who likes big bullets and cannot lie? Jeff Cooper. The man touched many facets of the firearms world and this is yet one more where he left his mark.
While actually designed by Tim LeGendre of LeMAG Firearms, the inspiration for the idea came from Cooper’s support for a “Thumper” cartridge.
Basically, a “Thumper” was a big bullet moving as fast as they could push it so that an AR could take big game at 200ish yards.
Keep in mind that this was before things like the .458 SOCOM and .50 Beowulf were invented.
LeGendre designed what he called the .45 Professional and delivered an AR chambered in that to Cooper himself.
Bushmaster was highly interested in producing the new design, but they needed ammo for it.
When LeGendre approached Hornady about making ammo for it, they requested a slight change to the design of the case – shortening it slightly so they could load the 250gr SST in it.
The change was approved and the final cartridge was renamed to .450 Bushmaster.
.308 Winchester
After a cool story like 450 Bushmaster, the history of .308 Winchester can be kind of boring. Maybe I should have saved the good story for last… oh well.
Back in the 1940s 300 Savage was used for a series of tests for the US military, Frankford Arsenal (the actual US Arsenal, no connection to the brand/company that operates today) saw the tests and liked the results.
They started playing with the design a little and created a case that was slightly shorter, with a little less taper, and thicker walls.
Really liking what they saw, they lengthed the case back to its original specs. Using more modern powders (“modern” by 1940s standards) they created a cartridge that was effectively almost identical to the performance of milspec .30-06 Springfield but with a much smaller cartridge.
Smaller means lighter, lighter means you can carry more of it, so all in all – a lot better.
Winchester saw the potential for this new cartridge and introduced it to the hunting world in 1952.
Two short years later, NATO adopted the 7.62x51mm cartridge as a standard.
Practical Applications
450 Bushmaster
Hunting.
That’s it, that’s the list. The end.
Okay, 450 Bushmaster was designed as a hunting cartridge that could take big game (talking moose-sized “big”) at 200 yards or closer. And if nothing else, 450 Bushmaster does that.
If you’re in a fairly close environment and you need a really big bullet moving quickly to drop something large and four-legged, .450 Bushmaster is a solid option.
However, it comes with some major downsides that make it pretty much useless in all other applications.
Recoil is a beast. 250 grains moving at 2,200 FPS out of a 7ish pound AR means you’re getting the felt recoil roughly equivalent to 12ga slugs.
You can mitigate this with a brake and a good stock, but it’s still a hard hitter.
While you can do things like zeroing at 200 yards to have a point-blank zero out to that distance, 450 Bushmaster is an elephant fighting gravity – and it ain’t no Dumbo.
You are very limited on range and 250 yards starts to push it.
While it starts off with almost 2700 ft.lbf at the muzzle, 450 Bushmaster falls below 1,000 ft.lbf before it hits 300 yards.
.308 Winchester
Everything.
Because of the age of the cartridge and how widely it was adopted by NATO, the military, LEO, and more, .308 Winchester can do basically everything.
Hunting? Oh ya, .308 Winchester has taken every game animal in North America in droves.
Long range precision? Sure, while newer 6mm cartridges are the newest hotness, .308 Win is still widely used by sport shooters, LEO, and competition shooters – although most people running .308 Win in competition do so in special divisions built for it.
SHTF? .308 Win can take game, defend your post-apocalypse bunker, put down mutants (I mean, probably), and is so massively produced and used that refilling your stockpile should be fairly easy.
You can handload .308 Win with every type of bullet under the sun, you can find factory ammo for it in every gunstore and bait shop in the nation, you can find replacement parts basically everywhere, and any rifle you want that is large enough can and probably does come with a .308 Win option.
It is the definitive do-all cartridge in North America.
I would argue that 6.5 Creedmoor is better, but there is no denying that .308 Winchester has achieved unparalleled success. [For more on that, check out our article 6.5 Creedmoor vs 308.]
Ballistics
The real meat and potatoes of these comparisons are how they actually stack up against each other ballistically. Well, in most ways – .308 Win kicks the snot out of 450 Bushmaster.
At the muzzle they are basically the same, .308 Win has around 2700 ft.lbf and 450 Bushmaster has just a few pounds under that.
The big difference is that .308 Winchester keeps at least 1,000 ft.lbf out to about 600 yards, 450 Bushmaster loses it by 300 yards.
While .308 can reach out accurately to 1,200 yards (if you’re pretty good), 450 Bushmaster is on life support by the time it gets past 500.
[To learn more about 450 Bushmaster ballistics and why it was created, see our recent article]
AR-10 Vs. AR-15
I’m going to assume that you’re looking at both of these calibers in an AR platform. While both can be found in bolt-action rifles also, 450 Bushmaster in a bolt gun is kind of silly.
The AR-10 is at least a couple of pounds heavier than an AR-15. It’s larger, less handy, and can quickly become a beast to hike with.
Generally speaking, an AR-10 is also more expensive to build or buy.
This is why “thumper” cartridges like 450 Bushmaster, 458 SOCOM, and 50 Beowulf exist. They give you basically the same punch as a short-action cartridge (at least for a couple of hundred yards) but keep the package small.
Personally, I say get both.
Wild Animal Defense
I’m a big believer in the idea that guns are not your best defense against most wild animals. For black bears, nothing beats a hiking song and some bear spray. For mountain lions, bringing a mule is technically the best but a hiking song and a sharp stick is a decent second option.
However, there are those times when nothing else will do. Maybe you tend animals that are looking really juicy this time of year, maybe you have a particularly mean set of critters in your area, whatever the case – you need a bigger stick.
.450 Bushmaster is one hell of a stick and in this role, it can really shine.
Most of the professional guides I’ve spoken with that live and hike in grizzly country say they choose a 12ga 3” magnum slugs as their last line of defense against a bear – that gives them about 2950 ft.lbf at the muzzle.
450 Bushmaster comes in around 2700 ft.lbf… but you can have 10 rounds in a magazine and less recoil.
If grizzly is your worst-case scenario, you might want to really consider a 450 Bushmaster or some other thumper as your next move.
What Is Better?
If you can stand the size and weight of an AR-10, then 308 Winchester is the clear winner.
But if you need something smaller and lighter – 450 Bushmaster is the ticket.
Really though, 450 Bushmaster is basically in the exact same boat as 50 Beowulf and .458 SOCOM.
They are all basically the same ballistically, they all have basically the same amount of ammo per magazine, they all cost basically the same, and more or less have the same issues.
I would give .458 SOCOM a slight edge in terms of reliability, but everything else really isn’t enough difference to make a difference.
Converting An AR-15 To 450 Bushmaster
The easy method is a new upper and modifying your magazines.
Magazines are standard AR-15 5.56 NATO mags, but with a new single stack follower. You can also get a dedicated 450 Bushmaster magazine.
For the upper, you’ll need a new barrel and a new bolt. 450 Bushmaster and .458 SOCOM use the same bolt face so it’s pretty easy to find.
A normal BCG can be used, it just needs the new bolt.
Overall, like most other AR conversions – 450 Bushmaster is pretty easy.
[Of course you can also buy a 450 Bushmaster complete upper and all the work is done for you. Just drop it on your standard AR-15 lower, pop 2 pins, and you’re ready to rock!]
Parting Shots
When it comes down to it – the “thumper” cartridges are all basically the same, just slightly different flavors.
If you need one, pick the one you like most and go for it!
But .308 Winchester will give you a lot more options and a lot more range. But that comes at the cost of a heavier rifle.
Let me know what you picked!
And let us know what caliber comparisons you want to see next!
