How to Mount an Aimpoint Red Dot on a Henry .450 Bushmaster Rifle

As a sponsor member of our local National Wild Turkey Federation chapter, Loki Incorporated gets a chance at winning a firearm at yearly fundraising banquets. At last year’s (2022) event, Loki won a Henry single-shot rifle in .450 Bushmaster caliber. This was a new caliber to me; I had heard of it as a cartridge for AR15-type Modern Sporting Rifles (MSRs), designed to fit within the magazine well size of those guns. I knew the creation of the cartridge had something to do with certain states’ restrictions against using bottlenecked cartridges for hunting large game. I hadn’t investigated it further, because I’m fortunate to live in a state with no such bullshit restrictions.

So, my investigation of the .450 Bushmaster caliber started serendipitously with winning a rifle chambered in it. It turns-out the .450 is nearly the ballistic equivalent of the legendary .45-70 in modern loadings, with all other factors (barrel length and bullet weight, mainly) being equal. The .450 was initially loaded by Hornady, adapting previous attempts to create a large diameter “Thumper” (the late Col. Jeff Cooper’s term) cartridge pushing a heavy bullet capable of whacking enemies or big game at relatively close range from a compact firearm. The concept is sorta like a .45-70, but the round works in an MSR. Hornady’s adaptation was successful, and now several different arms manufacturers sell not only MSRs, but conventional guns too, in .450 Bushmaster.

The .450 has a rebated-rim “straight-walled” case; it’s actually slightly tapered, enough to make feeding into the gun’s chamber easier than for a truly straight-walled case. The case has no distinct neck, though, making it acceptable to the drones who came up with the bottlenecked cartridge restrictions and demonstrating their ignorance of the terminal performance of small arms.

Why would I mess with a close-range, single-shot rifle in a “Thumper” caliber when I live and typically hunt in a state that has no bottleneck cartridge restrictions? Well, my deer hunting can be over open fields where high velocity .30 caliber arms excel or in hilly and thick cover where a short, handy gun capable of thumping a deer (or opponent) at face-to-face ranges would be useful. I thought it would be interesting to see if the Henry rifle would fit that role.

Henry .450 Bushmaster Rifle

The Henry .450 Bushmaster is only 37.5 inches long, but has a 22-inch barrel. The barrel isn’t threaded, so you cannot attach a muzzle device without gunsmithing. The gun is a lightweight, tipping the scales at about 6-¾ pounds, so it thumps at both ends when fired. Tiger-striped matte finished walnut furniture embellished with swivel studs complements the dark blued barrel and matte black receiver. The gun came with a brass bead front sight and a folding leaf rear adjustable sight, and was drilled and tapped for a Weaver 82 scope mount.

If my old eyes could accommodate the iron sights, I would have left the gun alone because I wanted to use it at short ranges for quick shots. But, that feat is getting more difficult for me each year, so I decided to mount a red dot sight on the rifle. I wanted a sight that was robust and wouldn’t easily hang-up on brush, and would allow me to quickly aim at my target with both eyes open. My choice was the Aimpoint Micro H-2 with a 2 MOA dot. This sight mounts to a “Picatinny” rail, and my measurements of my eye high above the rifle bore indicated the combination of sight and rail would center the red dot in my line-of-sight when I shouldered the rifle. Perfect! Now to mount the sight.

How to Mount an Aimpoint Red Dot Sight

I did a search online for a Weaver 82 compatible rail, as Henry didn’t offer any to fit the H015 rifle series my rifle belonged to, and immediately found several sites that sell them. The only problem was that no one sold a shortie version – the rear sight on my rifle is so close to the scope mount holes above the chamber that I would have to remove the sight to install a standard length base.

View of Rifle, Micro H-2 and Base

Also, as you can see from the photo even if I removed the rear sight or machined the rail to fit over the sight, the short chamber contour of the rifle would have require cantilevering the rail over most of its length. Bad Juju.

Rear Sight and Base

So, I mounted my optic on the rail and then checked how long the rail would have to be to include all three mounting screw holes and be well short of interfering with the gun’s rear sight.

Checking Rail Length

Once I determined and marked on the rail the length I wanted, I clamped it in my horizontal bandsaw and cut it off.

Cutting the Rail

Then, using some scrap cardboard in my machinist’s vise, I clamped the piece I intended to install on the rifle in the vise and smoothed the cut edges with files.

Filing the Rail

After cleaning the filed end of the rail, I used some aluminum blackening finish to “paint” the cut end of the rail.

Blackening the Rail

Fit Check

After a fit check to ensure the mount interfaced properly with the rifle and the mounting holes in the rail aligned with the ones in the gun, I degreased the scope mount holes on the rifle with carburetor cleaner.

Scope Mount Holes

Mounting Holes Degreased

If you use a solvent that produces hazardous vapors to degrease the holes, be sure to work in a well-ventilated and flame/spark-free environment. Also, if your solvent is in a spray can be sure to wear safety glasses to defend your eyes from spray kick-back, and use an apron to protect your clothing when you are spraying the stuff. After letting it work for a few seconds, use a cotton swab to soak up any degreaser that may have settled into the mounting holes.

Since the mounting screws that came with the rail had slotted heads, instead of hex or torx heads made for higher torque attachment, I used blue thread sealant in the mounting holes to secure the mounting screws.

Thread Sealant in Mounting Holes

Then, before the sealant could set-up, using a small torque wrench set to the rail manufacturer’s recommended level I installed the mounting screws through the rail into the mounting holes in the rifle.

Rail Attached

All that was left to do in the sight mounting process was to attach the Micro H-2 to the rail, using my small torque wrench to turn the sight mounting screw to the manufacturer’s recommended level.

H-2 Mounted on the Rifle

Henry .450 Bushmaster Rifle with Aimpoint Micro H-2

Henry and Ruger Rifles

For comparison purposes, I took a photo of the Henry rifle alongside my favorite deer rifle, a Ruger M77 Mk1, and a photo of their respective fodders.

.450 Bushmaster on Left, .30-’06 on Right

The Ruger is longer and heavier than the Henry, and the .30 caliber cartridge is longer than the .450. Notice the latter bullet has a larger diameter, and it is heavier by 100 grains (250 vs 150). The .30 caliber bullet leaves the gun muzzle at over 700 feet per second faster than the .450 and has about 250 foot-pounds greater kinetic energy because of its higher velocity (recall that Ek = 1/2 mV², so energy increases faster with increasing velocity than it does with increasing mass). Even so, the shape of the Henry’s stock, and its lighter weight combined with shorter length, causes the muzzle to rise more when I shoot it offhand than the rise of the .30-’06.

Now, the fun began! I got ready to take the rifle out to the range to test it, with the only commercial ammo I could find at the time, Hornady Custom with 250-grain FTX bullets. As part of my range preparation, I looked at the particulars of this round. On the cartridge’s web page under Specifications, you’ll be able to compare each of the .450 Bushmaster cartridges that Hornady loads, and also view the data for each cartridge in Hornady’s Ballistic Calculator. I reproduced the results for the 250-grain FTX load, below.

Ballistic Calculator for .450 Bushmaster

Looking at the results, I see the big slug slowing down rapidly, becoming subsonic somewhere between 300 and 400 yards downrange. Given a 100 yard zero, the bullet stays within a point-blank range (a dinner plate sized impact zone) from the gun’s muzzle out to nearly 200 yards, where it drops almost nine inches and loses nearly half of its kinetic energy. That tells me that if I do my part, I can make killing shots on deer-sized targets to nearly 200 yards by merely holding the red dot on my desired impact point when I fire the rifle. Given my intended use of the gun, that is more than enough range.

At the range, the rifle and cartridge combo truly is a thumper! The felt recoil is on a par with a 12-gauge turkey shotgun firing 3-inch magnum shells.

How to Mount an Aimpoint Red Dot on a Henry .450 Bushmaster Rifle

Henry .450 Bushmaster Rifle

How to Mount an Aimpoint Red Dot Sight

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