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ATI Milsport .450 Bushmaster Rifle Review

The ATI Milsport 450 Bushmaster rifle is an economical and powerful Information Age hunting firearm.

ATI Milsport .450 Bushmaster Rifle Review

The RIA Milsport 450 Bushmaster AR from American Tactical is a radical evolutionary adaptation of Gene Stoner’s original 1950’s-era space age black rifle. Sporting the same inimitable ergonomics and running an absolute mule of a cartridge the size of your finger, the Milsport 450 Bushmaster brings breathtaking power to the classic AR platform. While this nifty new gun would fit nicely in a squad car or blast a home invader straight to hades, it’s true mission just drips classic Americana. This gun wants to hunt.

Technology evolves over time. The ATI Milsport chambered in .450 Bushmaster represents the current state of the art in close to mid-range deer hunting rifles.

War Story

It was so cold that I actually had ice forming inside my rubber boots. My dad had rousted me out of bed at oh-dark-thirty for a quick dose of Froot Loops before I donned pretty much every piece of clothing I owned. We got to the woods while the sun was still someplace over Mongolia.

The ATI Milsport 450 Bushmaster takes all that is righteous and wholesome about Gene Stoner’s AR15 and optimizes it to take North American game.

I broke through the ice on the walk in and filled my boots with water. That took a toll on my normally sunny disposition. I was also a typical eight-year-old man-child. Sitting still and being quiet did not come naturally. Despite the sordid winter weather, and my many manifest age and gender-related handicaps, I still loved being with my dad in the Mississippi delta woods now slowly illuminating with the golden rays of a rising sun.

Clutched in my shivering fingers was one seriously radical smoke pole. The gun actually belonged to my mom, but she had sense enough to stay home where it was warm. As a result, this day I was packing her iron.

The pursuit of the whitetail deer is as old as humanity. Such stuff as this represented my formal introduction to fieldcraft and environmental stewardship.

The gun was a Ruger Model 44 semiautomatic rifle. Looking vaguely like an M1 Carbine and chambered in .44 Magnum, the Model 44 fed from a four-round tubular magazine and weighed six pounds even. This lightweight gas-operated bush rifle was scaled such that even a gangly eight-year-old could run it.

I was a good shot back then. My dad had seen to that. Over open sights I could put those big fat 240-grain jacketed hollowpoints into a teacup out to seventy-five yards or so.


The synergistic combination of the cold and my hyperactive comportment threatened to get the better of me. My fidgeting grew worse, and I began to pine for home. Throughout it all my dad sat motionless scanning the woods. He poked me gently in the arm and pointed without saying a word. In the distance, I caught movement. That’s when everything changed.

The cold was gone, and I sat still as a stone. As the deer moved noiselessly at a diagonal towards us he raised his head and I saw horns. My heart jumped into my throat, and my breath grew fast and shallow. The same thing has happened to every young hunter since the very dawn of time.

The .450 Bushmaster cartridge is absolutely gargantuan. Here is shown from left to right the 5.56mm, the .450 Bushmaster, the .44 Magnum, the 10mm Auto, and the .45ACP.

The buck grazed steadily until he was maybe forty yards away and then dropped his head down behind a tree trunk. I used the opportunity to raise mom’s rifle and lay the gold bead of the front sight on something furry. My dad gave my leg a little squeeze, and I was cleared hot. Time seemed to stop.

The deer’s next step brought his shoulder out from behind the tree. I steadied my sights, slipped off my safety, and squeezed the trigger just as I had been taught. I guess the gun had some substantial recoil and made quite a lot of racket. I didn’t feel or hear any of it. I had the rifle back on target instantly. However, that big thumb-sized slug dropped my first buck right where he stood.

The ATI Milsport 450 Bushmaster is a lot of gun for the money. Lightweight, economical, and immensely powerful, this Milsport rifle is optimized for its mission.tely gargantuan. Here is shown from left to right the 5.56mm, the .450 Bushmaster, the .44 Magnum, the 10mm Auto, and the .45ACP.

I safed the rifle and handed it to dad before scampering down the ladder. He followed at a more intentional pace and handed the gun back to me with an entreaty to be careful. I covered the forty yards in about two seconds and arrived just as the modest eight-point breathed his last. Enraptured by an eclectic amalgam of excitement, sadness, and awe, I ran my hand across the dead animal’s warm fur and began searching for entrance and exit wounds.

His rack wasn’t anything special, but it would look cool screwed to a board and hanging on the wall of my bedroom. Cleaning the beast gave me my first taste of both anatomy and wound ballistics, both of which would hold me in good stead through careers yet to come. I didn’t drink the animal’s blood or anything comparably vile to celebrate my first kill, but dad’s buddies did cut off my shirttail for reasons that seemed a bit opaque at the time.



That experience was a holy thing, a near-spiritual connection between creation and created. Hunting involves discipline, guile, and stewardship of both the land and the creatures that crawl, trot, or scamper across it. I could yet have become a man without those experiences, but I would have been some lesser sort.

The guts of the ATI Milsport 450 Bushmaster are classic Gene Stoner AR. The trim architecture makes for easy portage, while the direct gas impingement operating system is proven reliable.

Deer Slaying in the Information Age

The AR rifle has taken game both dangerous and otherwise from sea to shining sea. It was for this specific mission that ATI produced their new AR rifle chambered in .450 Bushmaster.

The breech face on the .450 Bushmaster (left) is bored larger than that of the traditional 5.56x45mm version.

The .450 Bushmaster cartridge began as the result of musings by Jeff Cooper. Jeff bemoaned the fact that the diminutive 5.56x45mm round was really inadequate to hunt proper North American game. In response, Tim LeGendre of LeMag Firearms dreamt up a large bore solution. LeGendre called his creation the .450 Professional. Cooper called it the “Thumper.”

Hornady found the case just a bit long to optimally accommodate its 250-grain pointed Flex-Tip bullet. By acclamation all involved agreed to shorten the round from 1.771 inches down to 1.700 and rechristened the new cartridge the .450 Bushmaster. The end result is a veritable monster.

The heavy muzzle brake helps tame the massive .450 Bushmaster’s prodigious recoil.

The .450 Bushmaster is a remarkably versatile round. These big fat cartridges squeeze into modified AR mag bodies equipped with appropriate followers. The included mags hold a dozen .450 rounds, but only reliably feed around eight. Since many states limit magazine capacity for deer hunting to two to five rounds, this is not an issue.

The big jacketed projectile flies flat out to two hundred yards. When zeroed at 150 yards the bullets will land about two inches high at a football field and roughly five inches low at twice that. When combined with the more than 2,700 foot-pounds of downrange horsepower the bullet projects you have the ideal brush gun.

ATI offers a fine set of backup iron sights as well.

I have a dear friend who once dropped an elk in New Mexico at 860 yards using a .300 Win Mag bolt gun he built himself from a steel billet. That guy can shoot. However, for us mere mortals, two hundred yards in cluttered Mississippi overgrowth is about as far as I like to shoot at something that’s actually breathing. At ranges such as these the .450 Bushmaster is tough to beat.

The Gun

The ATI RIA Milsport rifle is perfect for its intended mission. The sixteen-inch barrel sports a 1-in-24 twist and is threaded 5/8x32. The fifteen-inch KeyMod rail sports plenty of real estate for accessories. The full-length top rail obviously accommodates all manner of glass.

The Vortex UH1 Razor sight offers all the attributes of a genuine holographic sight along with some neat extras. The reticle projects out to infinity no matter the range to your target.

The operating system is direct gas impingement, so the gun is lightweight, slim, and reliable. The barrel has an ample contour for stiffness and recoil amelioration without being unduly bulky. The bolt face is unique to the .450 Bushmaster round, but the bolt carrier is otherwise classic AR.

The Stoner-inspired layout is institutional dogma for anybody who has ever hefted an M4. The rugged muzzle brake excises a bit of the thump from Jeff Cooper’s thumper. The gun is available with either a standard M4 collapsible buttstock or the fancy Luth-AR adjustable sort. The weapon comes with a bilateral single point sling mount at the rear aspect of the lower receiver. My gun also includes a nice set of ATI flip-up backup iron sights.

The reticle on the Vortex UH1 Razor is designed for quick acquisition under all lighting conditions.


I took my first deer over open sights, but we can do so much better nowadays. For the Milsport I mounted up a Vortex UH1 Razor holographic sight ( The Razor offers a true holographic reticle that is distortion-free out to infinity along with a built-in charging port. Stoke the sight with a rechargeable CR123A battery, and you can rejuvenate the rig via any handy USB cable. The Razor’s unique EBR-CQB reticle is purpose-designed for rapid close range engagements of the sort you might encounter while hunting in brush.

The EOTech G33 3x pivoting magnifier slaps into or out of your field of view as needed. It is milspec rugged.

Behind the Razor I set up an EOTech G33 pivoting magnifier ( This milspec rig pivots in and out of the line of sight as needed. Rubber armored and built like an armored fighting vehicle, the G33 offers 3X magnification that keeps you prickly out to the limits of the .450 Bushmaster cartridge.

Both of these devices are military-grade rugged. While that may be overkill for most civilian applications, such rarefied gear means your equipment will not be the limiting reagent on your next hunt. You’ll fail before it will.

The ATI Milsport 450 Bushmaster offers all you could want in a hard-hitting and maneuverable brush gun.

The rest of the gun can be customized to your heart’s content. Bravo Company offers quite literally anything imaginable. Aftermarket pistol grips, stocks, foregrips, and sundry ballistic ditzels — if you want it they’ve got it.

Off a simple rest at 25 meters the ATI Milsport 450 Bushmaster cuts a single jagged hole.

Trigger Time

This ain’t your daddy’s AR15. I had not realized just how spoiled I had become when throwing those zippy little .22-caliber bullets downrange. By contrast, the .450 Bushmaster is quite the manly round. While the gun is not necessarily painful, you’ll certainly know you’re shooting it. The experience is akin to running a lightweight 12-gauge.

Offhand at 50 meters the ATI Milsport 450 Bushmaster shoots plenty straight to put venison on the table.

The trigger is classic AR, so it has a little creep with a nice crisp break. The gun is pleasantly front heavy, so it drops back on target for fast follow up shots. Whether fired from a rest or while moving, the Milsport 450 Bushmaster shoots plenty straight out to reasonable ranges. That big fat bullet slows down quickly past two hundred yards, but carries immense energy closer than that. Whether it is a classic broadside shot at a football field or something closer and more cluttered, that massive 250-grain jacketed slug punches both hard and deep.

The .450 Bushmaster round is breathtakingly powerful. Not only did it shred this water-filled milk jug, the resulting hydrostatic shock splintered my stool.

When loaded with eight rounds in the magazine the gun was unflinchingly reliable. The box will hold twelve, but stuffing more than eight tends to slow the bolt unduly. However, for a hunting arm eight is more than adequate.

So long as you don’t cram more than eight rounds into the magazine the Milsport was monotonously reliable. Since many states limit magazine capacity for deer hunting to two to five rounds, this is not an issue.


All the things that make the M4 such a capable combat tool translate into exceptional efficiency in a hunting arm. The adjustable stock and inimitable human engineering make the gun adaptable to both young small shooters as well as burly old guys. Recoil is noteworthy without being scary, and the downrange thump is undeniably formidable. From the perspective of pure Newtonian Physics, the .450 Bushmaster is much like an oversized .45ACP bullet running more than two and one-half times as fast.

If you look closely you can see where the ejection port is milled out slightly oversize to accommodate the massive .450 Bushmaster round.

The same attributes that make the Milsport 450 Bushmaster such a capable harvester of venison would perform comparable service on feral swine or black bear. The capacity to accept combat-grade optics, while offering instantaneous follow up shots, makes the gun so much more capable than anything available back in my day. Fast, powerful, rugged, and cool, the ATI Milsport 450 Bushmaster is tomorrow’s deer slaying pig popper.

The .450 Bushmaster would be a great round for chasing black bear as well. The ATI Milsport gives the added benefits of handy maneuverability in tight quarters as well as rapid follow up shots.

ATI Milsport 450 Bushmaster Rifle Specs

  • Caliber .450 Bushmaster
  • Operating System: Direct Gas Impingement
  • Barrel Length: 16 inches
  • Overall Length: 35.75 inches extended; 32.5 inches collapsed
  • Weight: 8.7 pounds with optics; 7.2 pounds without
  • Forend: 15-inch KeyMod
  • Magazine Capacity: 8 Rounds
  • MSRP: $699.95
  • Contact: (800) 290-0065,

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