Thumper: Bushmaster 450 SD Rifle Review

A hard-hitting round with a lot of potential, the Bushmaster 450 SD Rifle has a home at the competition or tactical ranges, or in hunting situations.
Thumper: Bushmaster 450 SD Rifle Review

The author ran the Bushmaster 450 SD Rifle for the first time at Gunsite Academy where she put the gun through a number of tactical drills. (Photo: Kat Ainsworth)

It was October of 1980 when Soldier of Fortune magazine ran the late Col. Jeff Cooper’s article regarding prototype rifles made by Bertil Johansson of Aimpoint. The prototypes were chambered in .221 Fireball and .44 Magnum, the latter of which was Cooper’s preference, and featured an in-the-grip magazine and folding stock. Cooper had recently begun advocating for what he referred to as the “Thumper” and Johansson’s prototypes were one of the earliest attempts at making his concept reality. However, years – decades – would pass before Thumper became reality in the form of the .450 Bushmaster.

The .450 Bushmaster could easily trace its written roots to page 182 of Cooper’s "To Ride, Shoot Straight, and Speak the Truth." On that page Cooper begins outlining his thought process for the eventual cartridge’s creation, saying “We can and should do better, and I therefore propose Thumper.” Among other things, Cooper felt one shot from Thumper should be decisive – and it is. It was Tim Legendre of LeMag Firearms who ended up designing what he dubbed the .45 Professional cartridge which he later licensed to Bushmaster. Continuing the chain of ammo-events, Bushmaster turned to Hornady, Hornady shortened the case from 1.771 to 1.700, and the .450 Bushmaster was born.

The culmination of those events can be found in the latest firearm from Bushmaster, the Bushmaster 450 SD Rifle — there is also a carbine version but for this review the rifle model was used. The SD is, of course, chambered in .450 Bushmaster. After spending extensive time shooting and hunting with the rifle I have nicknamed mine Thumper. It’s less an ode to Cooper and more a statement of fact: the rifle produces significant - though manageable - felt recoil and drops deer and hogs in their tracks. One shot indeed.

A boar taken at night with the Bushmaster 450 SD Rifle and Trijicon REAP-IR thermal. (Photo: Kat Ainsworth)

About the Rifle

The Bushmaster 450 SD Rifle has a 20-inch 4150 chrome-lined barrel, a length that offers greater velocity than carbine-length while remaining short enough to be maneuverable. Because it’s made from 4150 steel the barrel has an edge when it comes to heat resistance; its chrome lining distributes heat more evenly and improves feeding. In addition, it has a 1:24 twist rate which is ideal for stabilization and accuracy of rounds such as the Remington Premier 260 grain AccuTip.

The rifle comes with a fixed Remington R-25 stock with a SuperCell recoil pad. The stock itself is a thumbhole style and has a broad, angled top; the pad is thick and made of cellular polyurethane. Since it cannot be adjusted the shooter must make their peace with working with the available length of pull. In my case it was a bit short, but the lack of length did not have a negative affect on my shooting. It also has a polymer Hogue pistol grip with no finger grooves.

In short, every component of the rifle is designed to enhance the performance of the heavy cartridge. That includes parts like the bolt which is made from Carpenter 158 steel; Carpenter 158 is case hardened for a more durable exterior, leaving the interior slightly more flexible, making it a better shock absorber. Even the Bushmaster-made muzzle brake is specifically designed for greater recoil reduction than previous designs.

Trigger Time

One of the first things you may notice when picking up the Bushmaster 450 SD Rifle is its weight: 7 pounds, 7 ounces, empty, meaning nearly nine pounds with a mount and optic. The pro of its weight is it offsets recoil but it is a bit hefty for spot-and-stalk hunting or shooting offhand. For the range review and field test I mounted a Leupold VX-5HD 3-15x44mm optic to Thumper. The optic leant fantastic clarity and a broad field of vision, and proved itself capable of stellar low-light performance. The combination of the .450 Bushmaster with the high-quality optic made it a promising setup. I was eager to run the gun on the range and in the wheat fields of Texas.

The rifle shouldered easily and the angled topmost edge of the stock provided a good cheek weld. The first time I fired it was at Gunsite Academy in Paulden, Arizona, during the height of the desert’s scalding heat. As a fan of larger calibers there was little doubt I would be interested in the rifle but as it turned out, I wasn’t only interested. I wanted one. Running the gun in Arizona I also used Leupold optics – their scopes are a good match for the power of the Bushmaster 450 SD – and had no trouble scoring bull’s eye hits at 50 yards. 50 yards wasn’t far, though, and I wanted to do more. I wanted to hunt. But first, testing.

Back home in Wisconsin I hit the range to zero my Leupold scope and put the rifle through its paces for accuracy. Once the scope was zeroed the rifle’s accuracy became immediately clear as it scored tight, one-hole groups first at 50 and then 100 yards. For testing I used Hornady 250 grain FTX and Remington Premier 260 grain AccuTip. Shooting from the bench using a sandbag rest, the best five-shot group at 100 yards using Hornady measured 1.12-inch while the best using Remington was 1.17-inch; on average, five-shot groups hovered around 1 MOA. Shooting offhand, groups broadened noticeably due to the weight of the rifle making precision challenging.

One of the most important components of a rifle is the trigger. The Bushmaster 450 SD comes with an ALG Defense ACT Trigger (ACT stands for Advanced Combat Trigger). It’s a well-made trigger: the curved trigger blade and hammer are 8620 alloy steel, the disconnector is 1070 High Carbon Steel, and all pins are 4140 Chrome-Moly. All trigger parts are HardLubed meaning they’re electroless Nickel-plated with an integral modifier and Boron or Teflon are used to improve surface hardness.

Factory pull weight is set to be no less than 5 pounds, 5 ounces; my Lyman Digital Trigger Pull Gauge read the trigger pull weight of Thumper as 5 pounds, 6 ounces. As for performance, the trigger delivers a smooth pull with only the slightest amount of grit detectable – so slight as to go almost unnoticed – and has a crisp break. Reset is short and allows quick follow-up shots.

At the range, the rifle performed well out to 100 yards. More importantly, the gun did well both in the dusty, dirty 90-plus degrees of the Arizona desert and in the snowy, windy sub-zero frozen tundra of Wisconsin. It was time to move on to the field test in yet another state: Texas.

One of four coyotes taken with the rifle and Trijion REAP-IR thermal. This coyote answered the call by coming in hot, and dropped in his tracks thanks to one shot from the Bushmaster. (Photo: Kat Ainsworth)

The Hunt

It’s always wise to double-check zero after a flight, so when I arrived at the Spike Box in Benjamin, Texas, I hit their range. Targets were set at 25, 50, 75, and 100 yards with an extra steel target set at 150. Under 100 yards targets were paper but at 100 and beyond they were steel (the 150-yard target was a steel donkey). The gun required an adjustment to return to zero but was quickly nailing tight groups at various distances.

One pro of hunting with a .450 Bushmaster is its sheer power. But the components that create that power also have a negative affect: a fast drop rate. Remington 260 grain AccuTip bullets dead on at 100 yards dropped eight inches at 150 yards and 17-plus inches at 200 yards. Because I was hunting, it was even more important to know where bullets would strike at various distances. Since I was also night hunting, I mounted the new Trijicon REAP-IR thermal to a second rifle; the second rifle exhibited the same drop rate as the first.

My first day hunting at the Spike Box we thought we were skunked. Whitetail deer were our first goal and we hadn’t seen any shooters. We decided to drive back early and keep an eye out for potential targets while we still had shooting light left and right as we were giving up, a pair of does darted from the treeline. I jumped from the truck, used the open window frame for balance, and fired two rapid shots at the fleeing deer. The doe dropped in her tracks. Despite the failing light the Leupold performed well and the shots fired were nearly touching one another, creating enormous wound tracts. Later in the hunt I used the thermal-mounted rifle to drop four coyotes, three of which were a triple at 150 yards. All the coyotes crumpled on the spot. Yes, you could say the Bushmaster 450 SD is a solid hunting gun.


There was a persistent issue with both rifles: failures to feed. Even clean and lubed they experienced failures periodically and, at times, would pick up the next round but the bolt wouldn’t move fully forward. In those cases, hitting the magazine release provided the impetus for the stalled round to slam home. There was an instance calling at night when a round had failed to fully chamber and I did not notice; a bobcat came in and the shot couldn’t be taken. At the time of the review the manufacturer said it’s a magazine issue and is being resolved.

Bottom Line

The latest from Bushmaster – my Thumper, if you will – has significant promise as an enjoyable hunting rifle. Larger calibers such as the .450 Bushmaster are gaining ground with hobbyists and hunters alike who prefer hard-hitting shock-and-awe to the lighter pings of smaller cartridges. In the past guns like Thumper were only available through custom builds and the occasional limited run rifle. But today we’re finally being given options from well-known manufacturers.

These rifles may not sell with the predictable frequency of a .223-Rem-chambered AR-15 but they will sell, and as word gets out sales will continue to rise. I, for one, prefer some extra “BOOM” to my guns whether at the range or in the woods. After all, who doesn’t want the surety of a big, bad bullet? Hopefully the Bushmaster 450 SD is just the beginning of a big-bore trend.


Manufacturer: Bushmaster

Model: Bushmaster 450 SD Rifle (also a Carbine model)

Action: Semi-Auto, Direct Impingement

Caliber: .450 Bushmaster

Finish: Matte Black

Stock: Black, Fixed, Remington R-25 with SuperCell Recoil Pad

Grip: Hogue Pistol Grip

Sights: None

Handguard:  AAC Square-Drop Handguard with Picatinny Rail

Barrel Length: 20”

Barrel: 4150 chrome-lined steel

Twist Rate: 1:24

Muzzle Threaded: 11/16x24

Muzzle Device: Bushmaster muzzle brake

Weight: 7 pounds, 7 ounces (empty)

Capacity: 5 round magazine

Overall length: 39.25”

Trigger: ALG Defense ACT Trigger

Trigger Pull Weight: 5 pounds, 6 ounces (measured)

Accessories: One (1) 5-round Magazine

MSRP: $1299


Remington Premier 260 grain AccuTip: average velocity: 2002 fps, standard deviation: 22.00, average group (100 yards): 1.32”, best group (100 yards): 1.17”

Hornady 250 grain FTX: average velocity: 2108 fps, standard deviation: 17.00, average group (100 yards): 1.23”, best group (100 yards): 1.12”

Velocity figures are averages of ten shots recorded by a PACT Professional XP chronograph. Groups are the result of five 3-shot groups from a sandbag rest at 100 yards unless otherwise noted.

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