This will most likely not work for .450 Bushmaster. While the bullets themselves are both .45 caliber, and similar in length, the parent casing is different. The .450 Bushmaster is based off the smaller .284 Winchester casing, while the .458 SOCOM is based off a crimped down .50 AE casing. As a result, the .450 Bushmaster cartridges may be loose in the magazine.