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450 Bushmaster vs. 308: Which Should You Choose?

450 Bushmaster vs 308
December 7, 2021 Edited October 25, 2023 32072 view(s)
450 Bushmaster vs. 308: Which Should You Choose?

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.

450 Bushmaster Ammo on Table


.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.

308 Ammo on Table


Practical Applications

450 Bushmaster


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 Rifle Live Fire


.308 Winchester


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.]



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.

308 vs 450 Bushmaster ballistics chart

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.


Grizzy Bear growling

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!

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Aaron Short
December 8, 2021
this may seem a little off topic but have you heard about Sig Sauer new MCX Raptor oh man it is sweet to be release in 2022 no specific date. but it is essentially a 7.62x51/308 8" barreled AR-10 styled sweetness so now would be your chance to build something similar to beat it to them to the punch
Russell Coble
April 25, 2022
That would be considered a pistol ar here in Michigan. I believe it's anything under 9 inch.
Eric Stafford
December 13, 2021
I went .450 Bushmaster. I don’t regret it but I do want to build a .308 Winchester AR-10 only because of the range. I have a .350 Legend, too. If you use a heavier buffer on the .450 Bushmaster recoil is significantly reduced. I had standard carbine buffer at first, couldn’t shoot more than about 10 shots at the range before your shoulder was getting sore. With a heavier buffer (A2 like 5.6 oz) went to the range and the recoil was greatly reduced, shot 15 rounds no problems. The action cycles better, as it is a little slower, too
December 13, 2021
I've got both and for specific reasons. My state only allows shotgun slugs and straight-walled cartridges in some counties, while allowing bottleneck cartridges in others. It's all about population density and deer. Considering a .350 Legend too for same reason too...
December 30, 2021
Great piece. Curious about the comment regarding 450BM being pointless in a bolt action. One of the reasons I opted for the Ruger American Ranch in 450BM (besides that I live in Ohio)is that it could be loaded hot and heavy for Brown Bear defense up north. Your cousins over at Bear Creek Ballistics have 240 and 285grain loads of 450BM for bolt-gun only that go toe to toe with 45-70. While the 308 has probably killed a grizzly or two in its day, not too many folks would bet their lives on it or expect a humane kill necessarily.
James Palmer
April 19, 2022
Bear Creek rocks,I am a Buckeye as well,I took a buck about 175 lbs with the Bear creek,it was a double lung shot it went about 20 feet,heart and lungs were evaporated basically looked like strawberry jello,great ammo for 450 BM.
Russell Coble
April 25, 2022
floyd collins
January 30, 2022
i have the bca 50 beo and i love the hard hitting cant wait to get my 450 bushmaster now for you little boys you should stay with the 556
Baron sellers
May 17, 2022
I love the 450 so much I've bought two uppers from BCA ! ( last one side-charging). Have taken numerous hogs with it and all one shot kills! Does the job extremely well.
March 22, 2022
"450 Bushmaster is an elephant fighting gravity and it ain't no dumbo ". This comment left me scratching my head... all objects fall at the same rate no matter the weight all else being equal. Remember that guy Newton? So the real factors affecting drop are SPEED and ballistic coefficient. If that 300 grain .452 bullet was pushed to the same velocity as a 223 m855 they would have almost the same trajectory and hold overs at any distance. Heavier bullets also have BETTER ballistic coefficient in most cases than light pointy bullets so in that same scenario the .452 bullets would most likely have better long range performance, at least before wind resistance did catch up to them.
April 23, 2022
Well spoken Dan i didn't wanna type all of that but you hit the nail on the head
Russell Coble
April 25, 2022
I chose a 5.56 ar15 and a 7.62 ar 10. Best of both worlds. Coming from a military background I believe in the standards.
August 22, 2022
Semper Fidelis Brother!!! Hell I like weapons regardless of caliber!!! Who’s with me on this???
David McKee
May 31, 2022
I actually think the BM would be better for the Zombie apocalypse. Hits hard. Easier firearm to carry and maneuver in tight quarters. The 250 yard range is not an issue; zombie killing is done at close range.
Darrell McAdams
September 14, 2022
My first "gun".was a 20 gauge shot gun. I was 11 at the time. I wasn't allowed a 22 rifle as they were too dangerous. They shot too far. Why, that 22 bullet might travel a mile before it stopped. I graduated to a 12 gauge by the time I was 12 years old. You were a sissy if he were afraid of the kick. I have had some that would bruise.your shoulder they kicked so hard. I purchased one of the 450 Bush Master and it doesn't kick any harder than many of those pump 12 gauge shot guns I have been shooting since I was 12 yrs old. I am old now, but 12 gauge is still my go to home defense choice.
Kevin C
September 17, 2022
I bought a BCA 450 bushmaster upper several years ago when they had them at a price I couldn't pass up. Using a standard buffer and Mako GL-Shock stock, the recoil was about like a 20 gauge with dove loads. I played with it for a while, then it ended up staying in the safe while I focused on other things. Then, life brought me a torn retina. After recovering from the laser surgery, I decided to try the 450 again after adding a Limbsaver slip on recoil pad. Now the recoil feels about like a .223. The range I belong to has large steel plates at a 45 degree angle to keep rounds from going over the backstop. The BOOM bouncing back from those plates is the only unpleasant part of shooting the 450.
david k godwin
October 5, 2022
I have a Savage MSR Hunter in 308, basically a AR15 weight with the 308 punch and very accurate. Its kinda custom with its adj.gas system and high end bolt with 5r rifling barrel but it looks and feels like a 7.5 LB ar15, very nice.
May 11, 2023
Cedric Richards Sr
July 18, 2023
I bought the BCA 458 SOCOM and love it. The only problem is ammo cost but need to save for that.
David Kurz
October 25, 2023
Went with the 450 Bushwhakker for the reason of SRP vs LRP's. Yup roll my own 300gn #'s David Tubbs flatwire spring & H3 buffer weight went in it before I even touched it off. A little bit more kick then the 223 WYLDE. Don't see any difference between the carbine & mid-legnth gas tube. Might of gained 25 fps? All in all great shootability. Thinking about the 400 Legand when available!! I'm an OLD Dude that loves the .400 seeds.
October 25, 2023
.400 Coming soon
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