What is the Best Barrel Length for the .450 Bushmaster?

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When it comes to big-bore cartridges developed specifically for use in the AR-15 platform, there are three main contenders to consider, the .50 Beowulf, .458 SOCOM, and the .450 Bushmaster. The .50 Beowulf was the first big-bore AR-15 cartridge and it helped to change how the AR-15 was viewed when it came to hunting. Designed by Bill Alexander, the .50 Beowulf was initially introduced at the 2000 Florida SWAT Round-up, and then publicly at the 2001 SHOT Show. Alexander developed the .50 Beowulf with one purpose in mind, to be the physically largest cartridge an AR-15 can accept.

The .50 Beowulf quickly became popular as a short-range brush busting hunting cartridge, and opened the eyes of many to the possibilities offered by the versatile AR-15 design. The next big-bore design introduced was the .458 SOCOM developed by Maarten (“Marty”) P. ter Weeme with rifles being built by Tony Rumore of Tromix. The .458 SOCOM was introduced in 2001 and it too quickly gathered a dedicated following among big game hunters.

The third and most popular of the AR big-bores is the .450 Bushmaster. Developed by Mr. Tim LeGendre, the owner of LeMag Firearms LLC, LeGendre had been intrigued by Jeff Cooper’s “Thumper” rifle concept. Cooper wrote about the possibilities a hard-hitting big-bore cartridge might have on man or beast at moderate distances. LeGendre liked Cooper’s idea, and in 2007 he began developing a cartridge using a large .45-caliber bullet. His design was suitable for use in an AR-15 and he dubbed it the “.45 Professional.”

It wasn’t long before Bushmaster Firearms became interested in the new cartridge for use in their rifles. This led to Bushmaster engineers working with Hornady to make the cartridge suitable for mass production. Hornady’s engineering team suggested some changes to the dimensions of the cartridge, and it became the .450 Bushmaster in 2009. The parent case for the .450 Bushmaster is the .284 Winchester. This straight-wall design features a 0.473-inch rebated rim with a base diameter of 0.500-inch. Neck diameter is 0.480-inch and it has a case length of 1.700-inches and an overall length of 2.260-inches.

One interesting design feature of the .450 Bushmaster, a blessing or a curse depending upon your point of view, is the use of 0.452-inch diameter bullets. While Maarten P. ter Weeme chose to use traditional 0.458-inch diameter rifle bullets in his .458 SOCOM design, LeGrendre and the engineers at Hornady went with the same bullet diameter as used in the popular .45 ACP pistol cartridge. Back in 2009, there were not many hunting bullet options in this 0.452-inch diameter suitable for use at the high velocities the .450 Bushmaster generates. Sixteen years down the road though and there are a number of designs suitable for big-game hunting readily available.

Of three “AR-15 big-bores” the .450 Bushmaster has seen the most success. The .50 Beowulf is a good design, but Alexander Arms is a small company which holds the trademark on the cartridge limiting its reach. While I have a Tromix .458 SOCOM carbine I love, Maarten P. ter Weeme’s cartridge has similar issues as the .50 Beowulf. Basically, they both suffer from a lack of support by a major company in the industry. The .450 Bushmaster is much more widely available, and has successfully moved beyond its “AR-15” roots into the realm of bolt-action rifles.

While I have quite a bit of experience with both the .50 Beowulf and .458 SOCOM dating back to the introduction of both of these cartridges, I have much less with the .450 Bushmaster. However, Firearms News magazine’s Editor-in-Chief Vince DeNiro, and his son Matthew, have spent quite a bit of time with it hunting in the woods of Ohio, and Vince formed his own opinions based on observations of its performance on white-tailed deer: “Many of us were extremely happy when Ohio approved straight-walled cartridges for deer as 12-gauge slugs do have a list of disadvantages. I immediately gravitated to .450 Bushmaster once it was approved, because I liked the idea of hunting with an MSR-type platform.

Although, we have hunted deer with handgun calibers such as 10mm, .460 Rowland, and .45 Win Mag in both pistols and carbines, these are primarily tree-stand guns inside of 35 yards. I have also hunted with .350 Legend. My younger son, Matthew, and I started off with Nosler-type 250-grain for .450 Bushmaster as that was all that was available early on. I was really impressed with the accuracy at 100 yards. Winchester’s 250-grain Deer Season would consistently shoot less than 1.5 inches for a five-shot group, while Hornady’s Custom FTX 250-grain came in at a little over an inch, 7/8 of an inch without the flier! This was out of a Windham 16-inch-barreled AR-15.”

DeNiro continues, “But, I live in the heavily wooded part of Ohio with hills and deep hollows. You usually don’t get a shot on a deer past 70 yards and most shots are under 45. After a couple of seasons, we had to switch to a heavier load because the deer would run 50 to 70-plus yards after getting hit in the lungs or heart, and they would always run deeper into the woods and down into a hollow; that meant a lot of exhausting work getting them out. A deer running even 100 yards after being shot on flat farmland, without a tree in sight, is not an issue, but here, deer disappear after about 30 yards in the thick woods. So, we tried Federal’s Non-
Typical Whitetail 300-grain hollow point. Matthew got the first deer with this load and the results were great—it may have run 25 feet at most before dropping. This fixed the issue.

Last year, Hornady asked me to try their new American Whitetail 245-grain soft point. I was hesitant to go back to a lighter load, but they reassured me that the jacket design should do what I want. It did. I got a large six-point buck at around 70 yards and all it did was move in a half circle; it died where I shot it. Of course, these are not laboratory conditions, and it’s only a result of one hunt, but I was impressed with the projectile. For .450 Bushmaster, I stick to my ACR rifle, and Matthew has been using his 16-inch Bear Creek Arsenal rifle for a couple of years. His is topped off with an ACOG since he played a lot of Call of Duty growing up!”

During a recent conversation with DeNiro, we mused on the performance of the .450 Bushmaster when fired from a shorter length barrel, such as from an AR-15 SBR or pistol—DeNiro was thinking along the lines of a handy tree-stand gun for deer season, or possibly bear defense. We were both curious as to how well the popular big-bore cartridge would perform from a short 10.5-inch barrel compared to the common 18-inch length. To find out, DeNiro gathered together four .450 Bushmaster loads and I contacted Bear Creek Arsenal requesting a 18-inch AR rifle and a 10.5-inch AR upper on short term loan for testing. Bear Creek Arsenal obliged sending a Flat Dark Earth-color rifle with an 18-inch barrel. I mounted the black 10.5-inch upper they sent onto one of my registered SBR receivers and got to work on the range.

The four loads DeNiro selected ranged in weight from 245 to 300 grains. They consisted of Hornady’s American Whitetail 245-grain Soft Point, Winchester’s Deer Season XP 250-grain, Remington’s Premier 260-grain Accutip, and Federal’s Non-Typical Whitetail 300-grain Hollow Point. Advertised velocities ranged from 2,200 fps to 1,900 fps and we both felt these four loads would provide an interesting look at how the .450 Bushmaster performs from these two barrel lengths.

Getting to work on a hot July day, the 18-inch .450 Bushmaster produced its highest velocities with Hornady’s 245-grain American Whitetail SP load. This averaged 2,217 fps and generated 2,674 ft-lbs of energy at the muzzle. This load also produced the highest velocities from the short 10.5-inch barrel. It averaged 2,060 fps and generated 2,308 ft-lbs of energy. So, this load only dropped 157 fps going from the 18-inch to the 10.5-inch barrel. That’s an average of 20.9 fps per inch of lost barrel. Frankly this is better than I expected. The accompanying chart reveals how all the loads performed in these two barrel lengths. The 10.5-inch barrel did better than I expected.

Accuracy of both barrels varied depending upon the load but both shot their best with Winchester’s 250-grain Deer Season XP. Recoil with all four loads is noticeable from the bench. The .450 Bushmaster definitely hits hard, which is why many hunters pick it for big game and pig hunting. Performance on white-tailed deer is very good with proper bullet selection.

Overall, I was impressed by the cartridge’s performance. It did well from both barrel lengths. That said, I did have functioning issues with the short 10.5-inch Bear Creek upper receiver. It seemed to be under-gassed and reliable cycling was an issue, with all four loads. The 18-inch upper though cycled without issue. The .450 Bushmaster is a popular choice for those interested in an AR-15 “big-bore” for both hunting and fun. While it’s not inexpensive to shoot, it is a lot of fun, and it has proven to be an effective short-range hunting cartridge. 

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