There is not a wide selection of factory ammo for the 450 Bushmaster, although Hornady appears to do a good job of satisfying the core applications with 250 grain SST and FTX products with a muzzle velocity of 2200 fps and a reach of nearly 300 yards on deer size game. Remington’s 260 grain AccuTip at 2,180 fps does the same. Still, available in AR gas operated and now in bolt action firearms, the 450 Bushmaster cartridge has greater potential.
Handload development efforts often begins with a search for comparables to see what the rest of the world is doing. By capacity and bullet diameter, the 460 S&W and 450 Bushmaster are very similar. The 460 S&W is a 0.020″ smaller in diameter, but a 0.090″ longer than the 450 Bushmaster so they both have a gross case capacity of 80 grains. However, the 450 Bushmaster operates at 36% lower pressure levels, consistent with its intended AR application. While the 460 S&W charges are in no way applicable, there is some good component data to draw upon.
Bullet type was not the point of focus in this exercise as much as bullet weight. My thinking was that once I knew the velocity potential of a given bullet weight, I could determine what applications might be suitable and use this information to gauge the suitability of specific bullets. As an example, if I was able to dial in a 300 grain weight from one of the pistol bullets I had on hand, I might want to go one to fully develop a load for the Hawk Precision 300 grain spitzer with 0.025″ or 0.035″ thick jacket.
Not pretty, but not a bad place to start
For all of the reasons detailed in Part 1, these are the bullets selected and this is how they were assembled. They all work well in heavy 45 Colt and 454 Casull cartridges, and all have been used many times in handloads for those cartridges.
The cannelure positions are irrelevant, as the cartridge headspaces on the case mouth and a taper crimp is employed to make sure there is a positive headspace locating point.
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Warning: Bullet selections are specific, and loads are not valid with substitutions of different bullets of the same weight. Variations in bullet length will alter net case capacity, pressure and velocity. Primer selection is specific and primer types are not interchangeable. These are maximum loads in my firearms and may easily be excessive in others. All loads should be reduced by 5%, and developed following safe handloading practices as represented in established reloading manuals produced by component manufacturers. Presentation of these loads does not constitute a solicitation for their use, nor a recommendation.
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The 185 grain loads were mostly for my own entertainment. The bullet construction is quite fragile at the attained velocity and they do not have a good ballistic coefficient to put the velocity to good use. They are, however, quite loud in report and the do churn up some exceptional muzzle flash.
The 250 grain through 300 grain bullet velocity from this rifles short barrel feels a bit like short barrel 45-70 Gov’t performance loads. The bullet construction toughens for the jacketed bullets and they make for excellent deer, hog and black bear loads. The 300 cast is a major penetrator and will break bone and pass through a great deal of tissue.
The 360 grain cast begins to adversely diminish case powder capacity and loses range and energy at a distance. It does work well, lightly loaded at subsonic velocities, where it generates the most energy and momentum of the Tail Boss loads.
In general, Lil’ Gun was the most efficient powder, generating the most velocity at moderate pressure levels. Re7 proved also to be very useful with full case loading and consistent performance. I do not use Win 296 or H110 as much since Lil’ Gun has been placed into greater use. Neither H110 or win 296 are good low density load powders as this tends to make for erratic burn rates and pressure tends to flatten out near max loads. Lil’ Guns tends to run a little hot and pressure tends to rise more quickly at near max loads.
Accuracy and starting over..
The Greenhill twist rate formula is a rough metaphor for bullet length and it is quite insensitive to bullet rotational speeds. Consequently it doesn’t work in many applications. Bullets of the same weight can differ greatly in length and the same bullet pushed out of the end of a long rifle barrel spins at a much higher rate than the same bullet pushed out of a revolver barrel.
Most 450 Bushmaster firearms have a twist rate of 1:20″ to 1:24, while most modern 45 caliber handguns have a twist rate of 1:16″ but, because of velocity differences, both bullets exit their respective barrels at a similar revolution per second rate. In this case, the subject bolt action rifle has a 16″ barrel with a twist rate of 1:16″ to accommodate longer bullets with higher ballistic coefficient that the typical 0.452″ revolver bullet. All of the handloads indicated above do well in firearms with a 1:20″ or 1:24″ twist. Accuracy is mediocre at best with a 16″ twist, which led me to….
What does a muzzle loader and Bushmaster have in common?
Remember the comment about finding comparables? There are a number of modern 50 caliber magnum muzzle loaders that thrive on triple charges of black powder and deliver MOA 300 yard performance. They ingest sabot mounted bullets, with most of the mounted bullets are 0.451″ in diameter.
Left, a 250 grain Hornady SST bullet used as a sabot projectile and as the bullet in the company’s 450 Bushmaster ammo. Far left is a 300 grain Hornady SST bullet used in the company’s 50 caliber sabot mounted bullets and not loaded in 450 Bushmaster ammunition.
There are others from various manufacturers, but these were good for testing the issue of bullet length versus twist rate and velocity and for getting to accurate handloads with a 16″ twist.
Above, 100 yard groups shot with spire tip bullets. Left 250 grain Hornady factory ammo, center 250 grain Hornady SST handload 3/4″, right 300 grain Hornady SST handload 5/8″. Clearly the shifted center of gravity or center of pressure were a good match for the 16″ twists.
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Warning: Bullet selections are specific, and loads are not valid with substitutions of different bullets of the same weight. Variations in bullet length will alter net case capacity, pressure and velocity. Primer selection is specific and primer types are not interchangeable. These are maximum loads in my firearms and may easily be excessive in others. All loads should be reduced by 5%, and developed following safe handloading practices as represented in established reloading manuals produced by component manufacturers. Presentation of these loads does not constitute a solicitation for their use, nor a recommendation.
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I believe this gives us two good hunting loads, one suppressed load and a starting point to fill out the rest. We’ll be back when we have had a chance to work through some more bullets. For anyone loading for a rifle with a slower twist, the first data set should deliver acceptable accuracy.
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