450 Bushmaster, Slow and Steady Wins the Race

If I had a rifle for every time I fell in love with an idea, the world would lay quietly in a torpid slumber beneath a blanket of heaped weapons strewn beyond the horizon. I was blessed with a vivid imagination since childhood. My mind is in a perpetual cycle of finding project ideas, digesting them mentally until my brain has either built the whole thing and tested its flaws, or until the same has been exhausted to the smoldering dumpster where ideas die. If it weren’t for the occasional successful brainstorm that ends with a nifty new project, I might lose my mind. This is a story about one of those.

450 Bushmaster cartridges loaded with Hornady 350 grain round nose bullets, these bullets were .458 until I swedged them down to .452 for the Bushmaster

I have long wished for a slow and heavy cartridge that could readily be used for subsonic launching of big, heavy bullets that will go a very long distance. There were many possible suspects; big bore cartridges, the Whisper family, and many others. I had long wished for a 510 Whisper, but my suppressor inventory ventured only to the .46 mark. Making the 510 and similar cartridges inapplicable. The next best thing for a diet of heavy and slow would then be something in the .45 realm.
But even then, .451 or .458? Why not both?

The .458 bore has a much larger and heavier selection of bullets, and they are easily swaged down to .451. Which makes a perfect fit for the 450 Bushmaster. The 450 enjoys quality brass from Hornady, making reloading a snap. And using mild charges for subsonic velocities would keep the brass life high. The straight walls of the cartridge would hopefully last to be reloaded again and again.
The beauty of my main rifle, the Desert Tech SRS A1 Covert, is its multi-caliber role. I have a pile of barrels accumulating for it in my safe, so starting this 450 project was as simple as a barrel, some dies, and some powder and bullets.
The sixteen and a half-inch barrel was made by ES Tactical, crowned and threaded for my SilencerCo Hybrid. It didn’t take long to start falling in love with this basically large pistol.
I found that the factory Hornady Black 450 Bushmaster ammunition was a good place to start. At 100 yards it was printing groups just under two inches, I was hoping for better so I tried my hand at reloading. A set of dies for the BM isn’t as easy to come by as other calibers, all I could find were Hornady and another set from Lee Precision. I opted for the Lee set, which I still don’t regret. The four die set has allowed me to load quite a bit of very precise ammunition.

Seeing as how my objective was to eventually reach a heavy subsonic load, I went ahead and ordered Lee’s .458 to .451 swage die. That way I could take advantage of the larger and heavier selection of bullets in the 458 family. I wasted no time in doing so, some of the first reloads I tried were Hornady 350 grain round nose bullets swaged down to 451. They did pretty well, but I wanted bigger, so I purchased a box of 405-grain lead bullets that had been made for the 45-70. The lead slipped easily through my swage die, and in no time they were 451’s.

Subsonic loads for the Bushmaster used 405-grain lead solids, these were made to shoot in the 45-70, but after running them through the Lee sizing die, they ran perfectly through my Bushmaster

I tried a couple different powders, but as usual, when it comes to subsonic shooting, IMR Trailboss powder was the ticket I needed. I was blown away with the consistency of the results, I was seeing velocities more consistent than anything I had loaded prior. Not only single digits but SD numbers in the 1-4 fps range. I was praying that this would translate into extremely accurate ammunition, it wasn’t bad but not as good as I’d hoped. Accuracy still averaged around 1-1.5 MOA at 100 yards, good enough to hit most targets of mine at the ranges we expected.

My excitement about this whole Bushmaster project was tripled when Mad Scientist/Gunsmith Eric Smith built me a second barrel, this time for my Desert Tech MDR. The MDR is a semi-automatic bullpup, it brings accuracy and multi-caliber universality to a compact and quality package. I couldn’t wait to try my same loads in the MDR, I figured it likely wouldn’t cycle the action but I wanted to try anyway.

The accuracy was almost the same from the MDR as from my SRS A1, but as I feared it would only cycle the faster supersonic ammunition. I am currently working on an alteration to make it cycle, if it works out, it may be the coolest thing ever.

The goal, of course, was to use this project for some very quiet hunting. Sneaking into bow range of animals is exciting enough, but the ability for movie quiet rifle shots with one MOA accuracy made it even more exciting.

This past season we were able to put it into use, and the results were exactly as I had hoped. We had eyes on a small group of mule deer that we could predict movements with some regularity, so a good hide was fashioned that would give a view of them with no more than 120 or so yards max range. As it turns out, a young buck made his way across the opening one dusky evening, and he wandered around the 60-yard line.
The hushed report of the Bushmaster made every ear in the group perk up, but only one of them jumped. He jumped from the impact of the bullet, which hit him right above his right elbow, and passed through him exiting almost exactly opposite. He ran for about 20 yards where he toppled over and kicked on the ground for a short time.

This young buck hoped to escape from the Bushmaster, but a perfect shot through both lungs shortened his run to a 20-yard dash before he toppled

Internal inspection of the buck showed perfect damage to his lungs, the bullet passed through both lungs rupturing many vital passages along the way. His lungs quickly filled with blood, causing what most of us would call a near-perfect kill. Another positive result was very minimal meat damage, the lower velocity didn’t seem to cause all the bloody mess that supersonic bullets tend to do. It was more reminiscent of an arrow wound.

With experiences like this and all the other advantages that it brings, this will likely not be the last time we use the 450 Bushmaster for a hunt. While the purpose I have described here today may not be orthodox, it shows you what can be done with a little imagination and firepower.

-CBM

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