July 20, 2018
By James Tarr
The Windham Weaponry .450 Thumper is both a completely modern take on the AR-15 in an unusual caliber and a throwback to some of the concepts of the late Jeff Cooper. Before getting to that, you might be wondering who the heck Windham Weaponry is.
The first two AR-15s I ever owned I pieced together from parts made by Bushmaster/Quality Parts Inc. of Windham, Maine. When Remington bought that company a little over 10 years ago, it decided to move all the manufacturing of Bushmaster guns to one of the Remington facilities a little farther south. The laid-off folks at the former Bushmaster/Quality Parts Inc. facility had some tough decisions to make, and what they decided to do was continue to do what they did best: make AR-15s, now under the name Windham Weaponry.
This background is key. Back in the dark ages of the mid-'80s, if you wanted a reliable AR-15 you could spend way too much money for a Colt, spend a lot less money for a Bushmaster or buy mil-spec parts from Bushmaster/QPI and build one yourself. Long before I ever had dreams of becoming a gun writer, I took my Bushmaster M4 clone and decided to see how many rounds I could put through it without cleaning or lubing before it would jam. After 1,000 rounds without an issue, I got bored and stopped keeping track. The people who built those solid Bushmaster rifles and parts back in the day are the same people who make this Windham .450 Thumper rifle.
At its heart the .450 Thumper is a 16-inch-barreled AR-15 with a free-floating barrel and a fully adjustable fixed stock, chambered in the big .450 Bushmaster cartridge. The barrel is constructed of 4150 chrome-moly vanadium 11595E steel with a 1:24 twist. The barrel is threaded and tipped with an A2-style flash hider sized up to fit the bigger bore.
The bore and bolt carrier are chrome lined. The bolt is machined from magnetic particle inspected Carpenter 158 steel. This AR sports the traditional direct-impingement operating system and a carbine-length gas system.
The barrel looks absolutely massive. For the first 7.5 inches it is a full one inch in diameter, and at the muzzle it is 0.75 inch. If this was a standard .223 rifle, that would put it upwards of nine pounds empty, but you have to remember there is a 0.45-inch hole down the center of this barrel. The rifle is much lighter than it looks and balances over the center of the magazine well. Even with the fully adjustable Luth-AR buttstock, it is only 7.2 pounds empty.
The 13-inch aluminum handguard has M-Lok mounting slots at three, six and nine o'clock and two QD sling swivel sockets at the muzzle end. Windham has thoughtfully provided two QD sling swivels—one installed in the handguard and one in the QD socket on the buttstock. Windham also includes a black nylon sling; it's a basic entry-level piece as slings go, but it works.
The rail atop the handguard has T-slot markings, but the rail slots in the receiver are unmarked. The upper and lower receiver are standard forged items. In addition to the standard lower receiver markings, the left side of the upper receiver has "WW" and ".450 THUMPER" etched in white.
This rifle sports a Hogue OverMolded rubber A2-style pistol grip, and GI-style trigger components and charging handle—all the same controls that should be familiar to anyone who has ever used an AR-15.
With the Windham Weaponry .450 Thumper it would be easy to argue that everything is connected in some way. As I mentioned, it sports a fully adjustable Luth-AR fixed stock, designed by Randy Luth. Luth founded DPMS/Panther Arms, which was also bought by Remington, just like Bushmaster.
To be honest, I've never really liked the looks of the Luth-AR stock—it seemed a little "busy" to me in appearance—but during testing I found it to be perhaps the quickest and easiest to adjust adjustable AR stock I've ever examined. And ergonomically, it was spot on. Fully collapsed it provides a 13.5-inch length of pull. That can be quickly increased by an inch, and the cheek riser can elevate 7/8 inch off the stock.
Big-Time Big Bore
Now, about that caliber. I consider the .450 Bushmaster to be the first of the big-bore AR cartridges, a lineup that now includes the .50 Beowulf and .458 SOCOM and several other wildcats. The concept behind the .450 Bushmaster can be traced back to the later firearms guru Col. Jeff Cooper's "Thumper" concept.
He theorized that a semiautomatic rifle chambered in a hard-hitting cartridge with a bore diameter of at least .44 would be ideal for most big game hunting out to 250 yards. Considering this rifle is named the .450 Thumper, it appears the folks at Windham are giving credit where they think credit is due.
The .450 Bushmaster was originally a wildcat called the .45 Professional and was developed by Tim LeGendre of LeMag Firearms based on the .284 Win. case. Working together with the folks at Bushmaster and Hornady, the case length was shortened to 1.7 inches, and the cartridge became the .450 Bushmaster.
The standard loading for the .450 Bushmaster features a .45 caliber bullet weighing between 250 and 275 grains, although some specialty loads like the Underwood copper solids are as light as 220 grains. It's roughly equivalent to the .45-70 Gov't, although the cartridge itself is more compact.
Most of the velocities listed for this cartridge are from 20-inch barrels, so out of shorter tubes like the 16-incher on the Thumper you'll get slower than advertised speeds. Expect to see an 1,800 to 2,100 fps reduction, depending on the load.
The only parts changes needed on an AR-15 to make it .450 Bushmaster compatible are a new barrel and bolt. The bolt face has to be opened up to accommodate the wider cartridge. Then there's the magazine.
The .450 Bushmaster cartridge is designed to fit and feed from standard-size AR magazines. One five-round hunting magazine has been provided with the rifle, and externally it looks just like a 20-round .223 magazine. Even the feed lips are unchanged. The only difference you'll note is the follower has been designed for single-stack feeding. The .450 round is so much wider than the .223/5.56 cartridge the AR magazines are originally designed for that they stack in the magazine single file, and so a 20-round .223/5.56 magazine body holds only five rounds of .450.
Currently, Windham Weaponry sells only these five-rounders, and caliber-specific .450 magazines with more capacity are a little tough to find. However, the only things different about ".450 Bushmaster" AR-15 magazines are their followers. I know people have used stock .223 aluminum and steel magazines without a problem or ground down the top of their followers to help the fat .450 sit closer to the middle.
Perhaps the quickest solution is to go to Chamber Tactical and buy some of its purpose-built Big Bore AR-15 followers designed to convert standard steel and aluminum AR mags to properly feed fat cartridges like the .450.
The Chamber Tactical followers are only $9 apiece, and they work. With these followers installed, a traditional 20-round AR magazine body holds about nine rounds of .450, and a 30-round magazine body holds 12 to 13. FYI, you won't be able to use Magpul PMags with the .450 Bushmaster cartridge. Those magazines have a dividing ridge running down the inside front of the magazine body that interferes with fit and feeding of the .450.
Ammo options for the .450 Bushmaster are a bit limited. Hornady and Remington are the only major ammunition manufacturers to offer loadings, but Underwood Ammo offers at least two different loadings for the round—although they're twice as expensive as Hornady or Remington.
I find I am amused and delighted by these big-bore AR cartridges. Maybe it's because they look so cartoonish, too short and fat to be "real." My teenage boys pull them out of the box and laugh because they're shaped like mini brass cigars. My fiancé thought the Hornady red-tipped FTX cartridges looked like lipstick tubes.
I've fired all three of the big bores—50 Beowulf, .458 SOCOM and .450 Bushmaster—and they all have similar recoil impulses, although the Beowulf kicks the most because it's sending the most foot-pounds downrange with each pull of the trigger.
The recoil of the .450 Bushmaster is not abusive, but it definitely is different than the .223/5.56. Perhaps the best comparison would be firing slugs out of a 20-gauge semiauto shotgun. The gun shoves you with each pull of the trigger, but the shoves don't hurt.
For a rifle cartridge, the .450 Bushmaster is a bit slow, so most people recommend a 150-yard zero if you think you might be using it at distance. With a 150-yard zero, most .450 Bushmaster loads will hit within four inches from the muzzle out to past 200 yards. If you're a hunter, that might be a hindrance depending on where you live and hunt. However, if you hunt in heavily wooded states, like where I live in Michigan, you know 100 yards is a long shot and 200-yard shots are rare.
While the .450 Bushmaster might be a bit much for whitetail deer, it's just right for hogs. A 250-grain .45 caliber bullet traveling at or near 2,000 fps will roll hogs with ease. And I once watched a fellow gun writer take down a 1,600-pound Indonesian water buffalo with a 16-inch-barreled .450 Bushmaster AR during a hunt set up to evaluate the new Remington Hog Hammer ammunition line.
The writer was skeptical of the 275-grain Barnes solid-copper hollowpoints' ability to penetrate a 1,600-pound animal, so he purposefully pounded five of those slugs into the buffalo's breadbasket. It ran off but went only about 100 yards before expiring.
Examination showed those relatively slow-moving bullets expanded fully, and as a result they barely penetrated into the chest cavity of the big animal—but it means they still penetrated eight to 10 inches of heavy bone and muscle. That's more than enough for deer or hogs, maybe black bears. Remington ultimately decided not to introduce that load, although I still had some on hand for testing.
While a lot of the talk about this cartridge and rifle concern hunting, some of our special-ops soldiers have used big-bore AR rifles like the .450 Bushmaster for blowing hinges off doors and disabling vehicles. It's hard to argue with mass.
The .450 Thumper is definitely a niche firearm, but the theory behind its creation is a valid one, and the .450 Bushmaster round continues to perform. Whether you're looking for an offbeat medium-size big game rifle or just want something unique with which to have fun at the range, the .450 Thumper will do it. To be honest, useful hunting tool aside, it's also just a lot of fun to shoot.