Testing showed that reducing a .450 Bushmaster barrel from 18 inches to 10.5 inches resulted in only modest velocity loss roughly 150 fps in some loads. While the shorter barrel maintained strong energy and accuracy, it experienced cycling issues due to under-gassing. For reliable performance, a traditional 16–18 inch barrel remains ideal, though a tuned short barrel can still deliver effective short-range hunting power.
Among big-bore cartridges designed for the AR-15 platform, three names dominate: .50 Beowulf, .458 SOCOM, and .450 Bushmaster.
The .50 Beowulf broke new ground as the first major big-bore AR cartridge, followed closely by the .458 SOCOM. Both earned loyal followings among hunters wanting serious short-range power from a familiar platform.
However, the .450 Bushmaster ultimately achieved the widest commercial success. Backed by major industry support and adapted for both AR-15s and bolt-action rifles, it has become the most mainstream of the trio especially in states requiring straight-wall cartridges for deer hunting.
Inspired by Jeff Cooper’s “Thumper” concept a hard-hitting semi-auto rifle for moderate distances the .450 Bushmaster was developed in the mid-2000s and standardized in 2009. It uses a straight-wall case derived from the .284 Winchester and fires a .452-inch diameter bullet.
That bullet choice initially limited projectile options, but over time manufacturers have expanded offerings, providing multiple hunting-ready loads tailored to big game.
In states like Ohio, where straight-wall cartridges are legal for deer, the .450 Bushmaster quickly gained popularity. Compared to shotgun slugs, it offers flatter trajectories, improved accuracy, and faster follow-up shots from a semi-automatic platform.
Field reports from experienced hunters show strong terminal performance, particularly with heavier bullets in the 260- to 300-grain range. While lighter 245- or 250-grain loads shoot flatter, some hunters prefer heavier projectiles for quicker drop on deer in dense woods.
The traditional barrel length for a .450 Bushmaster AR-15 typically falls between 16 and 18 inches. But what happens when you cut that down to 10.5 inches for a compact tree-stand rifle or defensive setup?
To find out, testing was conducted using two firearms from Bear Creek Arsenal:
Four factory loads were evaluated, ranging from 245 to 300 grains.
The 18-inch barrel produced expected velocities, with Hornady’s 245-grain load averaging just over 2,200 fps.
The surprise came from the 10.5-inch barrel. Despite losing 7.5 inches of barrel length, velocity dropped by only about 157 fps with the same load roughly 21 fps per inch removed. That’s a smaller loss than many shooters would anticipate from such a dramatic reduction in length.
Even with the shorter barrel, muzzle energy remained well above 2,300 ft-lbs with lighter loads still plenty for deer or hog hunting at practical distances.
Both barrel lengths delivered respectable accuracy, with the 18-inch configuration performing flawlessly in cycling.
The 10.5-inch upper, however, experienced reliability issues. It appeared under-gassed and struggled to cycle consistently across all tested loads. While velocity and accuracy were promising, dependable function would require tuning.
Recoil from both configurations was noticeable, particularly from the bench. The .450 Bushmaster remains a hard-hitting cartridge which is precisely why many hunters choose it.
From a ballistic standpoint, the cartridge holds up better than expected when shortened. For close-range hunting especially inside 100 yards a 10.5-inch barrel does not significantly handicap performance.
That said, reliability is critical in a hunting rifle. A properly tuned short-barrel setup may offer a compact and effective option for tree stands or thick brush, but the traditional 16- to 18-inch barrel remains the safer bet for out-of-the-box dependability.
The .450 Bushmaster continues to prove why it dominates the AR big-bore category. It delivers serious stopping power, strong real-world performance on deer, and compatibility with straight-wall regulations in many states.
While trimming barrel length does reduce velocity, the loss is not as severe as expected. With proper setup, a short-barreled version can remain effective though reliability tuning may be necessary.
For hunters seeking big impact from an AR-15 platform, the .450 Bushmaster remains one of the most practical and proven options available.
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