Exploring the Effective Range of a .450 Bushmaster

While “Big Bore” mania has been circulating for a while now, a newer cartridge is finding its way to the head of the popularity pack: The .450 Bushmaster.

If you want a closer look at the history behind this powerful cartridge, its specifications, who it’s for and how to build a .450 Bushmaster rifle, then you’ll love this article.

Let’s get started!

History of the .450 Bushmaster

When Col. Jeff Cooper, a United States Marine who fought in WWII and the Korean War, was in the heat of battle, he needed rounds he could depend on for powerful, armor-piercing shots and deadly accuracy.

The rounds commonly used by military forces at the time just weren’t enough for him.

So, when he got back home, Cooper came up with the idea of a cartridge similar to the one found in his .45 ACP pistol that would work for a wider variety of firearms.

LeMag Firearms took his idea and ran with it, creating the .45 Professional cartridge that was later turned over to Hornady so that they could mass-produce the cartridges for Bushmaster’s AR-15 rifles.

It was dubbed the .450 Bushmaster.

The .450 Bushmaster wasn’t widely used until recently, and now, the round is being produced by major manufacturers including Federal, Buffalo Bore and Remington.

Why the sudden interest?

A relatively new change in gun laws makes it so that hunters in the Midwest can now use straight-walled cartridges in their semi-auto weapons.

A posse of medium-game hunters that were itching to use their AR’s flocked to ammo shops and many ended up choosing the .450 Bushmaster because of its reasonable price.

Now, the .450 BM is one of the most popular straight-walled cartridges on the market.


Savage 110 450 Bushmaster
Savage offers an accurate and affordable package for firing the .450 Bushmaster.

.450 Bushmaster Specifications

The .450 Bushmaster’s dimensions come in just under maximum legal limits, maximizing power and distance.

Here are the specifications:

  • Rim diameter: .453 inches
  • Overall length: 2.25 inches
  • Shell-case length: 1.7 inches
  • Bullet sizes: Between 245 and 300 grains.
  • Muzzle velocity: 2,200 ft/s, 200-yard velocity at 1,500 ft/s.
  • Muzzle energy: 2,700 ft/lb, 200-yard energy at 1,200 ft/lb.

This cartridge packs a serious punch, but what about its range?

450 Bushmaster Winchester Ammo
Winchesters .450 Bushmaster ammunition is a great choice for deer hunting.

Bushmaster .450 Effective Range

With as much energy as this cartridge generates, you’re going to get a larger range.

I found this was definitely true for the .450 Bushmaster that was giving me between 1.5 and 2.5-inch groupings at 100 yards.

That was a lot more accurate than my .45-70’s were getting.

Pace that out to 200 yards, and I was still getting some great accuracy. 300 yards is about the max range for this cartridge as it will start seriously dropping.

The optimal conditions for longer-range shots would be shooting from a stand during mild, windless weather.

Also, to maximize range, you’ll want a high-quality scope like the EOTech XPS Holographic. Speaking of scopes, let’s talk building.

Building a .450 Bushmaster Rifle

If you’ve already got a standard-built AR-15, then you’ve got half of a .450 Bushmaster rifle in your hands.

With a few tweaks to the upper assembly, I created a killer weapon that wasn’t too hard on the wallet.

The first thing I did was pick up a .450 Bushmaster upper assembly. Rock River Arms makes a great assembly that I’ve been very pleased with, but any assembly that fits a 5.56/.223 receiver will work.

The next (and MOST IMPORTANT) thing I did was change out the mags.

If you don’t do this, you can get some massive misfeeds and a lot of headaches. Lancer mags seem to work well — especially if you throw on some Tromix followers.

Boom. Now you’ve got a completely operable .450 Bushmaster rifle with minimal effort.

You WILL want to fit your rifle with some sort of muzzle device if you want to keep your shoulder in working order.

I like the Precision Armament Hypertap because it effectively mitigates the powerful blast generated by .450 BM.

If you don’t already own an AR and still want to get in the .450 game, I highly recommend the Ruger American Rifle Ranch that is already set up and ready to go for .450 Bushmaster cartridges.

450 Bushmaster AR-15
Any standard AR-15 can be converted to fire the .450 Bushmaster, but you can always buy one that is already optimized.

Why Use the .450 Bushmaster?

There are several reasons I got into shooting .450 Bushmaster.

But the main reason ended up being the fact that I could use this cartridge in places that I couldn’t use traditional bottlenecks.

It’s great for clean, quick and humane kills on medium-sized game like deer, elk, hogs and some bears.

It deftly out-performed the .350 Legend at the 250 to 300-yard range.

It also maintains much greater downrange energy than other rounds like the .223 Remington, which makes the .450 Bushmaster a great choice for competitive shooting as well as hunting.

The .450 BM is also very reasonably priced.

450 Bushmaster Buffalo Bore Ammo


Overall, this newly-popular round is exceptional at getting your shot further downrange with maximum power.

Here are some of the highlights:

  • Accurate
  • Legal for more areas
  • 250 to 300-yard effective range
  • Easy to build from an already-owned AR-15

So, if you’re looking to blast a hog, take down a deer across the field, or place in the top scorers at competition, you don’t want to overlook the .450 Bushmaster.

Have you tried the .450 Bushmaster cartridge? What did you think of it? Let us know in the comments below!

The Mission of Cheaper Than Dirt!'s blog, The Shooter's Log, is to provide information—not opinions—to our customers and the shooting community. We want you, our readers, to be able to make informed decisions. The information provided here does not represent the views of Cheaper Than Dirt!

Comments (31)

  1. When Col. Jeff Cooper, a United States Marine who fought in WWII and the Korean War, was in the heat of battle, he needed rounds he could depend on for powerful, armor-piercing shots and deadly accuracy.

    The 5.56 NATO rounds commonly used by military forces at the time just weren’t enough for him.

    I hate to tell you this, but 5.56 rounds were not used in WWII or Korea. They did not see use until Vietnam.

  2. How does this weapon compare to my Marlin 444? My gun has been around for 25+ years, and had given me similar results. The bullets even look similar. My gun’s range is excellent for a saddle gun, and there are few large game that have walked away once I got a bead on them.

  3. I built and upper out of quality parts. Faxon 18” barrel, Aero precision XL upper receiver, Faxon bolt carrier group, buffer spring and buffer recommended for 450 BM. Bought 5 different magazines, because of all of the trouble people have posted about feed problems. ( I have not tried your recommended magazine combo).
    This thing I s a cannon, love the power, but it fails to feed constantly, and in all different scenarios. It may be that it needs to wear in more. Not sure..
    Accuracy, in real world, off the shoulder, I’m good for 75 yards, maybe still needs to break in the barrel. Maybe I’m a terrible shot. But compared to my 308’s, the 450BM is not accurate. I need more time with this gun. I will try your mag suggestion.

  4. I would like to see a comparison with the .460 Magnum. I’m always looking for my next large bore revolver.

  5. I have been on the fence about my next rifle purchase. I’ve eyed the 450 BM for a little whilr but keep coming back to the .308. I live in Florida so there aren’t a lot of opportunities for many 1000yd shots. I primarily hog hunt hogs so this article is helping me to
    finally decide, although in the back of my mind I’m thinking the 308 would serve me better in a SHTF scenario. Hell maybe ill just buy both.

  6. Recently built a Bushmaster on. Savage Axis action using a Rhineland 16” barrel with 1/16” twist. Rifle loves the 250 grain FTX and 300 grain XTP-MAG Pushed by Lil Gun powder. Velocities are 2236 and 2995 FPS respectively. 1” at 100 yds for the FTX and 1.4” at 150 yds For XTP.

  7. What would be the cost of turning my Bushmaster .223 into a .450 Bushmaster and what parts will be needed? Will the parts have to be sent to a FFL or can they be shipped directly to me?

  8. This was a very interesting and well-written article on an ammo I knew nothing about. Thank you. However, I presume the author had an only momentary lapse when he said the 5.56 was commonly used in WW2 and the Korean war. I’m sure he meant the .30-06.

  9. This is an interesting article, but I shy away from calibers that are costly to shoot. I dont have any need or desire for the .450BM. I’m ok with the 5.45mm NATO. Added a 300 BLK recently and may get out of 7.62mmx39 altogether since there are more bullet loadings in 300 BLK that make it more versitile than 7.62×39.

  10. I doubt that Colonel Cooper had much contact with 5.56 rounds during World War II or Korea. They just weren’t that common. Perhaps you meant to say some other NATO round. Otherwise very interesting article. Thanks for sharing.

  11. The article is incorrect in regards to the 5.56 NATO M16 being used in WWII and the Korean War. The 223/5.56 NATO was accepted by the U.S. Military in 1963 well after both wars. I’m going to guess you meant the M1 Carbine 30 caliber which was basically under powered for what it was used for. The .450 BM definitely is and improvement over the 30 caliber in power and Muzzle energy.

  12. I just got a new .450 Bushmaster and really love it so far. I’m a reloader and already reload for .45 Colt and .45 ACP and have a lot of .451-.454 bullets. The fact that it’s a straight wall cartridge is why I chose this over the .458 Socom. Also the fact that you don’t have to deal with neck creep etc makes it nice. Make sure you plan to get single stack style magazines though as the offset double-stack AR type mags just don’t feed this round well. I’m loading it with Hornady XTP Magnum 300 & 243 grain hollow points, which have worked terrific on game with my .45 colt carbines at these velocities. The FTX is ok for target/defensive shooting, but I find that it opens too quick on deer size varmints and damages a bit of meat.

  13. The 5.56 x 45 NATO wasn’t in use during World War II and Korea. It’s introduction into the US Military didn’t happen until 1964 (and it wasn’t formally adopted by the NATO countries until 1980, even though it had been in service for 16 years), long after Col. Cooper’s Military Service ended in 1955.
    Col. Cooper was dissatisfied with the .233/5.56 x 45, and helped with the development of what eventually became the .450 Bushmaster, but it was for its use on Large Game out to 250 yards, not its use as a battle rifle. The calibers used during Col. Cooper’s service would have been the 30-06, .30 M1 Carbine, and .308/7.62 x 51 NATO. His experiences with the M-16/AR-15 would have been entirely post military.
    Just noting a historical inaccuracy in the article.

    1. Thanks for the polite correction (not all comments have been as cordial). We’re in the process of verifying the information and updating the article.


  14. The 450BM is an excellent “brush gun” caliber as well. I sent half its 250 grain bullet through a 2×6 fence board’s edge at 15yds and onward to a 50yd target, and yet the bullet strayed less than 6″ from the bullseye.

  15. From the experience I’ve had with my .450 BM, everything in the article adds up, plus I learned a couple things. I agree that you should really look into getting mags specifically for it. They say you can use standard AR-15 mags, but I had a ton of feeding issues, and most of the time, I just ended up feeding them manually one by one. It does pack a serious punch to your shoulder, even with the Buttstock that I bought for it. I’m good for 20-30 rounds at the range with it before I just don’t want to put anymore impact on my bruised shoulder. I’ll have to try out a new scope for it too, seeing as the optic I had for my 5.56 wasn’t really cutting it. Couldn’t get very good grouping. Good to know the effective range is 250-300 yards. I’d love to get it dialed for hunting.

  16. First I wanted to say thank you for all the information. In your article When you mentioned having to switch out the standard .556 magazine, and you recommended LANCER. Is it a proprietary magazine to the 450 or does one .556 magazine feed the .450 better than the other? If so can you send me a link to the magazine that you recommended we try to have the best experience possible. Thanks again.

  17. I have it in the Ruger American ranch rifle… it pushes the Barnes 290 grn tipped boattail muzzleloader bullet at 2150 fps and will shoot cloverleaves at 100 yds. Weighs a hair over 6 1/2 lb with a Hawke slug IR scope … it is currently my favorite deer gun, and the best brush gun I have ever used.

  18. The .450 BM is exceptionally accurate out of an AR-15 platform using the Hornady 250gr. FTX load. Sub-MOA is not at all unusual.

  19. I just purchased a ruger 450 American rifle with a 22in barrel over the typical 16. I took it to range with several boxes of Hornady Black 250 grain. I ranged at 60 yards using a Strikefire II red dot. It took a good hour to get it dialed in and producing tight patterns. I am not a professional just a hunter trying out this combination because I have been looking for a new deer rifle. I’m not sure how it will perform when its 30, in a tree but its lighter and pretty manageable for the longer barrel. Oh it has a kick and it’s very loud even with the muzzle break.

  20. I built a 450bm last year I love the round shoots great but I’m still having feed issues. Can’t rely on maltable shots. Not that you need them with the 450 bm.. One hell of a wallop!!!!

  21. I have had and shot a 450 BM for two years and it is more accurate than this article states. I have shot a deer in the ear at 193 yards off a bench the gun can do it I cant without help from a bench. At 65 yards a perfect between the eyes. Both shots were witnessed no bull. I shoot the Ruger American and love it. PS my scope cost more than the gun.

  22. Good article except 5.56 NATO rounds were not commonly used by military forces during WWII and the Korean War.

  23. Do you think Ruger would consider making a .450 Bushmaster in semi auto just like the .44 magnum they’ve made for years? What a nice little NE deer rifle that would make with the increased energy over the .44.

  24. The 5.56 NATO round wasn’t adopted by the US military until 1963. The Korean conflict ended in 1953. So, that round wasn’t used at the time. The small arms ammunition in use for rifles in WWII And Korea includes 30-06, .30 carbine, and .45 ACP (Thompson machine gun).

  25. Hey good article. I’ve been wanting to get more info on this rifle round. I’ve been thinking about building one for hunting myself.


  26. Hello, I’m not sure if you realize that the 5.56/M16 was not put in service until Vietnam. The way the second and third paragraph is written makes it sound like Col Cooper used the 5.56/M16 in WWII and Korea and we know that is not accurate. Anyways, thanks for the article

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