Ammo Boxes

450 Bushmaster Ammo

450 Bushmaster ammo is a straight-wall, rebated-rim centerfire rifle cartridge chambered in .452-inch (11.48 mm) diameter bullets, designed by Tim LeGendre of LeMag Firearms and licensed to Bushmaster Firearms International for use in AR-15, M16, and M4 platforms with modified upper receivers and single-stack magazines. The .450 Bushmaster (11.48x43mmRB) fires 150-grain to 395-grain projectiles at muzzle velocities between 1,900 and 2,240 feet per second (fps), generating 2,200 to 2,800 foot-pounds of energy (ft-lbf) from a 20-inch (508 mm) test barrel. The cartridge was developed from the Thumper concept popularized by gun writer Jeff Cooper, who wanted a large-bore (.44 caliber or greater) semi-automatic rifle cartridge capable of one-shot kills on big game at 250 yards (228.6 meters or m). The Sporting Arms and Ammunition Manufacturers' Institute (SAAMI) rates the .450 Bushmaster maximum average pressure at 38,500 pounds per square inch (psi) or 265 megapascals (MPa). This guide covers .450 Bushmaster history, cartridge specifications, factory ammunition from Hornady, Remington, and Bear Creek Ballistics, ballistic testing at 100 and 200 yards, trajectory and zeroing, hunting applications by game type, straight-wall regulation compliance, and comparisons with the .308 Winchester, .30-06 Springfield, .45-70 Government, and .458 SOCOM (Special Operations Command).

History of the .450 Bushmaster Cartridge

The .450 Bushmaster descended from Jeff Cooper's Thumper concept, which called for a .44-caliber or larger cartridge in a semi-automatic rifle platform that could deliver lethal terminal performance on big game at 250 yards. Cooper was dissatisfied with the 5.56x45mm North Atlantic Treaty Organization (NATO) cartridge (.223 Remington) used in the AR-15, and LeGendre responded by developing the .45 Professional cartridge in the early 2000s using the .284 Winchester as the parent case. LeGendre built and delivered an AR-10 chambered in .45 Professional to Cooper for evaluation.

Bushmaster acquired the .45 Professional concept in 2007 and contracted Hornady to manufacture the ammunition. Hornady shortened the case from 1.772 inches (45 mm) to 1.700 inches (43.18 mm) and the overall length (OAL) from 2.362 inches (60 mm) to 2.260 inches (57.40 mm) to fit the AR-15 platform instead of the larger AR-10 and to accommodate Hornady's 0.452-inch 250-grain pointed Super Shock Tip (SST) flex-tip bullet. The .452-inch diameter is a very common bullet size shared by the .45 Colt, .45 Automatic Colt Pistol (ACP), .454 Casull, and .460 Smith & Wesson (S&W) Magnum. Cerberus Capital Management purchased the .450 Bushmaster rights in 2006, and the cartridge became part of Freedom Group alongside Remington Arms, Marlin Firearms, and Advanced Armament Corporation (AAC). Franklin Armory purchased Bushmaster out of Remington's 2020 bankruptcy and restarted rifle production in 2021.

Cartridge Specifications

The .450 Bushmaster uses a rebated, straight-wall case derived from the .284 Winchester with a bullet diameter of .4520 inches (11.48 mm), a base diameter of .5000 inches (12.70 mm), and a rim diameter of .4730 inches (12.01 mm). The rebated rim measures smaller than the case body, which allows the cartridge to feed from modified AR-15 magazines. There are 7 critical dimensions for the .450 Bushmaster case:

• Bullet diameter: .4520 inches (11.48 mm)
• Neck diameter: .4800 inches (12.19 mm)
• Base diameter: .5000 inches (12.70 mm)
• Rim diameter: .4730 inches (12.01 mm)
• Rim thickness: .0540 inches (1.37 mm)
• Case length: 1.700 inches (43.2 mm)
• Overall length: 2.260 inches (57.4 mm)

Case capacity is 59.5 grains of water (3.86 cubic centimeters or cm³). SAAMI maximum average pressure is 38,500 psi (265 MPa). The cartridge single-stacks in AR-15 magazines: a 10-round AR-15 magazine body yields a 4-round .450 Bushmaster magazine, a 20-round body yields 5 to 7 rounds, and a 30-round body yields 9 rounds.

Factory Ammunition Offerings

Five manufacturers produce factory .450 Bushmaster ammunition as of 2025: Ammo Inc., Federal, Hornady, Remington, and Winchester, with bullet weights ranging from 200 to 300 grains across hollow point, soft point, Full Metal Jacket (FMJ), and flex-tip designs. Starline manufactures empty brass for handloading.

Hornady .450 Bushmaster Ammunition

Hornady loads 2 factory .450 Bushmaster cartridges that use the company's proprietary bullet designs. The 250-grain FTX (Flex Tip eXpanding) Hornady BLACK load launches at 2,200 fps from a 20-inch barrel, generating 2,691 ft-lbf of muzzle energy, and the FTX bullet's polymer tip initiates expansion at velocities as low as 1,400 fps while the InterLock ring mechanically locks the jacket to the core for weight retention. The 245-grain Soft Point (SP) load fires at 2,200 fps with 2,633 ft-lbf of muzzle energy and uses an exposed lead tip for rapid expansion on thin-skinned game.

Remington .450 Bushmaster Ammunition

Remington offers 3 factory loads for the .450 Bushmaster. The Premier AccuTip fires a 260-grain polymer-tipped bullet at 2,180 fps with 2,749 ft-lbf of muzzle energy, and the AccuTip's boat-tail design improves ballistic coefficient for flatter trajectory at extended distances. The UMC (Union Metallic Cartridge) Centerfire Rifle load uses a 260-grain FMJ at 2,040 fps with 2,402 ft-lbf for range practice at lower cost. The Core-Lokt 260-grain Pointed Soft Point (PSP) fires at 2,040 fps with 2,402 ft-lbf and uses the Core-Lokt controlled expansion design for hunting applications.

Bear Creek Ballistics .450 Bushmaster Ammunition

Bear Creek Ballistics manufactures 4 .450 Bushmaster loads in 2 bullet weights with standard and high-velocity (HV) options. The 240-grain HV and 200-grain HV loads use increased powder charges for higher muzzle velocities compared to the standard 240-grain and 200-grain loads. The 200-grain loads offer reduced recoil and flatter trajectories for shooters who prioritize speed over heavy-bullet momentum, while the 240-grain loads balance velocity and bullet weight for general-purpose use.

Ballistic Testing and Performance

Ballistic testing of .450 Bushmaster ammunition reveals significant velocity and energy differences between factory loads at 100 and 200 yards, with Hornady loads retaining more energy downrange than Remington loads of comparable weight.

Testing Methodology

To test .450 Bushmaster ballistic performance, fire each load through a chronograph at measured distances from a fixed rest, recording velocity in fps and calculating energy in ft-lbf using the formula: energy = (bullet weight in grains × velocity² ) ÷ 450,240. Test barrel length affects muzzle velocity — factory ballistic data uses a 20-inch (508 mm) barrel, and shorter barrels reduce velocity by 25 to 50 fps per inch lost.

100-Yard Performance

At 100 yards (91.4 m), 3 factory loads produce the following terminal ballistics:

• Hornady 250-grain FTX: 1,775 fps velocity, 1,749 ft-lbf energy
• Hornady 245-grain SP: 1,773 fps velocity, 1,709 ft-lbf energy
• Remington 260-grain Core-Lokt: 1,592 fps velocity, 1,462 ft-lbf energy

The Hornady 250-grain FTX retains 287 ft-lbf more energy at 100 yards than the Remington 260-grain Core-Lokt, a 19.6% advantage driven by the FTX's higher muzzle velocity and superior ballistic coefficient. The Hornady 245-grain SP trails the FTX by 40 ft-lbf at 100 yards despite launching at the same muzzle velocity because the round-nose profile creates more aerodynamic drag.

200-Yard Performance

At 200 yards (182.9 m), the Hornady 250-grain FTX retains 1,462 fps velocity and 1,186 ft-lbf of energy. The 200-yard energy exceeds the 1,000 ft-lbf threshold that hunters use as a minimum for ethical whitetail deer kills, confirming the .450 Bushmaster FTX load as effective to 200 yards on medium game. Energy drops below 1,000 ft-lbf between 225 and 250 yards depending on atmospheric conditions, barrel length, and elevation.

Close-Range Terminal Performance

At 4 yards (3.7 m), the 245-grain Hornady SP achieves 2,240 fps muzzle velocity and 2,792 ft-lbf of energy. Close-range impacts at these velocities produce severe wound channels through hydraulic tissue disruption, making the .450 Bushmaster effective for hog hunting in dense brush where engagement distances average 15 to 40 yards (13.7 to 36.6 m).

Trajectory and Zeroing

The .450 Bushmaster follows a pronounced parabolic trajectory compared to smaller-diameter rifle cartridges because the large-diameter, heavy bullets have low ballistic coefficients between .185 and .210 G1. A 40-yard zero (the 40/140 zero method) places the bullet's second crossing of the line of sight at approximately 140 yards, keeping the trajectory within ±3 inches of point of aim from 0 to 150 yards. The 40/140 zero works for the .450 Bushmaster because the cartridge's trajectory rises 2 to 3 inches above the line of sight between 60 and 100 yards, then drops back through zero at 140 yards.

The Hornady 250-grain FTX drops approximately 8 inches at 200 yards, 22 inches at 250 yards, and 42 inches at 300 yards with a 140-yard zero, which limits the .450 Bushmaster's practical hunting range to 200 yards for most shooters. Wind drift at 200 yards averages 5 to 7 inches in a 10 mile-per-hour (mph) or 16.1 kilometer-per-hour (km/h) crosswind.

Hunting Applications by Game Type

The .450 Bushmaster serves as a short-to-medium range hunting cartridge for whitetail deer, feral hogs, black bear, and elk at distances under 200 yards, and the straight-wall case design qualifies the cartridge for use in states that restrict bottleneck rifle cartridges during firearm deer seasons.

Whitetail Deer and Straight-Wall Regulations

Michigan, Ohio, Indiana, and Iowa permit straight-wall cartridges during firearm deer seasons in zones that previously allowed only shotguns and muzzleloaders. The .450 Bushmaster became the primary straight-wall deer cartridge in the Midwest after Michigan approved straight-wall cartridges in the Limited Firearm Zone in 2014. The 250-grain FTX and 260-grain AccuTip produce 1,700 to 1,750 ft-lbf at 100 yards — more than sufficient for whitetail deer at Midwest hunting distances of 50 to 150 yards (45.7 to 137.2 m). Use expanding bullets (soft point, FTX, or AccuTip) that create 1.5 to 2.0 times original diameter wound channels for fast, humane kills.

Feral Hog Hunting

The .450 Bushmaster excels at feral hog hunting because the heavy .452-caliber bullets penetrate the thick gristle plate (the subcutaneous shield of cartilage and scar tissue on a mature boar's shoulder) that deflects smaller-caliber projectiles. Bonded-core and monolithic copper bullets in the 250 to 300 grain range maintain structural integrity through the gristle plate and break the shoulder joint behind the plate. The AR-15 platform allows fast follow-up shots on multiple hogs in group encounters.

Black Bear and Elk

The .450 Bushmaster generates enough energy for black bear at distances under 150 yards (137.2 m), where the 250-grain FTX still delivers over 1,400 ft-lbf. Elk hunting requires bullet placement within 100 yards for reliable penetration through the elk's heavy shoulder bones and dense muscle, and 260 to 300 grain controlled-expansion bullets provide the penetration depth needed for vital organ access on broadside shots. The .450 Bushmaster is marginal for elk beyond 125 yards because energy drops below the 1,500 ft-lbf threshold for consistent lethality on animals weighing 700 to 1,100 pounds (317.5 to 498.9 kilograms or kg).

Comparison with Other Large-Bore Cartridges

The .450 Bushmaster occupies a specific performance niche between medium-bore rifle cartridges and heavy lever-action rounds, with trade-offs in range, energy, recoil, and platform compatibility.

.450 Bushmaster vs .308 Winchester and .30-06 Springfield

The .308 Winchester and .30-06 Springfield fire .308-caliber (7.82 mm) bullets at higher velocities with superior ballistic coefficients, giving both cartridges 400 to 600 yard effective ranges compared to the .450 Bushmaster's 200-yard limit. The .308 Winchester drives a 168-grain bullet at 2,680 fps with 2,680 ft-lbf of muzzle energy, and the .30-06 pushes a 180-grain bullet at 2,700 fps with 2,913 ft-lbf. The .450 Bushmaster generates comparable muzzle energy to the .308 but loses energy faster downrange due to lower ballistic coefficients. Choose the .450 Bushmaster over the .308 or .30-06, if hunting in straight-wall-only zones or if engagement distances stay under 150 yards.

.450 Bushmaster vs .45-70 Government

The .45-70 Government fires heavier bullets (300 to 500 grains) at lower velocities (1,600 to 2,000 fps) from lever-action and single-shot rifles. The .45-70 generates higher muzzle energy with 400-grain and heavier loads, but the .450 Bushmaster offers semi-automatic fire from the AR-15 platform with faster follow-up shots. The .45-70 handles a wider range of bullet weights for handloaders, and modern .45-70 loads in strong actions (Ruger No. 1, Marlin 1895) reach pressures and velocities that exceed the .450 Bushmaster's SAAMI limits. The .450 Bushmaster qualifies as a straight-wall cartridge in states where the rimmed .45-70 may not meet specific case geometry requirements.

.450 Bushmaster vs .458 SOCOM

The .458 SOCOM fires .458-caliber (11.63 mm) bullets compared to the .450 Bushmaster's .452-caliber (11.48 mm) and uses a longer case with more powder capacity. The .458 SOCOM drives a 300-grain bullet at 1,900 fps with 2,405 ft-lbf, and subsonic loads using 500 to 600 grain bullets at 1,000 fps suppress effectively with suppressor-equipped AR-15 upper receivers. The .450 Bushmaster has more factory ammunition options and broader availability than the .458 SOCOM, and the .450 Bushmaster is chambered in bolt-action rifles by Ruger, Savage, Mossberg, and Remington in addition to the AR-15 platform.

Rifles Chambered in .450 Bushmaster

The .450 Bushmaster is chambered in AR-15 semi-automatic rifles, bolt-action hunting rifles, and single-shot platforms from 6 major manufacturers. Ruger chambers the AR-556 Multi-Purpose Rifle (MPR) semi-automatic and the Ruger No. 1 single-shot falling-block rifle in .450 Bushmaster. Savage, Mossberg, and Remington offer bolt-action hunting rifles. Franklin Armory manufactures the XO-26 BFS-III (Binary Firing System III) equipped AR-15 pistol in .450 Bushmaster. Bushmaster Firearms resumed manufacturing .450 Bushmaster rifles in 2022 under Franklin Armory ownership.

AR-15 conversions require a dedicated .450 Bushmaster upper receiver assembly with a .450-specific barrel, bolt carrier group, and single-stack magazine follower. Standard AR-15 lower receivers, buffer tubes, stocks, triggers, and pistol grips work without modification. The .450 Bushmaster uses a 1:24 twist rate barrel optimized for 200 to 300 grain bullets, and barrel lengths range from 16 inches (406.4 mm) for carbines to 20 inches (508 mm) for full-length rifles.

Handloading .450 Bushmaster Ammunition

Handloading the .450 Bushmaster requires Starline brass, large rifle primers, and medium-burn-rate powders matched to bullet weights between 150 and 395 grains. Starline is the primary manufacturer of new .450 Bushmaster brass, and cases last 5 to 8 reloading cycles before the straight-wall design shows case-head separation. Use a firm taper crimp to prevent bullet setback during magazine feeding — the .450 Bushmaster's short OAL and straight wall create higher bullet-pull resistance requirements than bottleneck cartridges.

Hodgdon H110, Lil'Gun, and IMR 4227 are the most common powders for the .450 Bushmaster, and charge weights are not published here because load data varies by bullet weight, seating depth, and primer type. Consult current published load manuals from Hornady, Hodgdon, or Lyman before assembling any handloaded ammunition. The .450 Bushmaster accepts .452-diameter pistol bullets in addition to rifle-specific projectiles, which expands the available bullet selection to include cast lead, plated, and jacketed designs from 150 to 395 grains. Subsonic handloads using 300 to 395 grain bullets at 1,000 to 1,050 fps work effectively with suppressed AR-15 upper receivers and require reduced powder charges and dedicated muzzle devices or suppressors.

Recoil and Mitigation

The .450 Bushmaster generates approximately 22 to 25 ft-lbf of free recoil energy in a 7.5-pound (3.4 kg) AR-15, which is comparable to 12-gauge shotgun slug recoil and 2 to 3 times higher than .223 Remington recoil at 3.7 ft-lbf. Three methods reduce perceived .450 Bushmaster recoil in the AR-15 platform:

• Muzzle brakes redirect propellant gas through side ports and reduce felt recoil by 30% to 50%, but muzzle brakes increase muzzle blast noise and concussion to the shooter and bystanders
• Heavier buffer weights (H2 or H3 buffers at 4.6 to 5.4 ounces or 130.4 to 153.1 g) slow the bolt carrier velocity and spread the recoil impulse over a longer time period
• Adjustable gas blocks reduce the volume of gas entering the gas tube and lower bolt carrier velocity, which decreases bolt impact force against the buffer and reduces felt recoil

Recoil pads and buttstock spacers add cushioning material between the buttplate and the shooter's shoulder, reducing peak recoil force transfer. Compensators with top-venting ports reduce muzzle rise without the side blast of muzzle brakes.