The AR Thumper Calibers

I know I’ve talked about this before, but a friend started talking about really wanting a 458 SOCOM upper, and it came back into my thoughts.

Starting with black powder rifled muskets the human race has constantly had a “big, heavy, slow” rifle option for hunting. With the introduction of black powder cartridge rifles some of these even made quite a name for themselves in Africa and on the American plains hunting big game. Everything from Antelope to Zebra so to speak. Companies like Sharps, Winchester, Remington, and even various Martini rifles in Africa, with their single shot precision, proved perfectly adequate to the task of killing man and beast alike.

However, the engine of progress turned, and the reign of black powder cartridge rifles was short lived by historical time standards, rather rapidly being replaced by smokeless powder offerings. But, even as the wheel of progress moves us forward into the future, the biology of big game animals hasn’t changed, so the advantages of a big, heavy, rifle slug at moderate velocities is still with us, even if the trend has been towards high velocity medium and small bore rifles for the killing of two legged animals.

Now we have an interesting array of cartridges that give us the “volume of fire” capable from a semi-automatic rifle, combined with the ballistics of a 140 year old single shot rifle.

I guess the three most common, for the AR-15 platform are:

50 Beowulf
450 Bushmaster

The 50 Beowulf launches a 300 to 400 grain bullet between 1,800 and 1,900 fps. That puts it within spitting distance of the 50-70 Government cartridge which launched a 400 gr bullet up about 1,850 fps, from a single shot rifle.

The 458 SOCOM launches a 300gr projectile to 1,900 fps, which is faster than the old 45-70 in a “Trapdoor Springfield” load which pushed a 325gr projectile to 1,600 fps.

The 450 Bushmaster also compares favorably to the old 45-70, although its heaviest load, a 260gr bullet at 2,180fps has no direct comparison to the old 45-70 round. But the Bushmaster is rather unique in that it was designed to launch heavy .452″ pistol bullets fast rather than .458″ rifle bullets slow, which makes it the most economical option to handload of the three listed here.

Ironically, none of these thumpers have been a runaway success in the market, after all those who like hunting with big, slow bullets already have lots of options that have already come and gone (and some that experienced a bit of a rebirth like the 45-70). And the places where you might need a heavy “stopper” bullet are generally situations where you don’t need a lot of shots, as the odds of being attacked by a solitary bear are much, much greater than being attacked by a gang of bears. So bolt action rifles in 458 Win Mag, 338 Win Mag, and other “Africa and Alaska” calibers are selling moderately well, as are 45-70 lever action rifles (many in Marlin’s excellent Guide Gun configuration).

So the hunters aren’t flocking to the AR-15 in thumpers, and the tactical crowd isn’t. The 300 Blackout has the market covered for short ranged, harder hitting options, and the 6.8 SPC and 6.5 Grendel rounding out that segment nicely.

So where do these thumpers fit in? Well, I don’t know. Maybe with a bush pilot who needs to keep a rifle for safety, but wants it as small and light as possible to not take up valuable space and weight in the plane. Maybe for someone who is recoil sensitive who needs a serious option in bear country. But it comes down to someone who needs a big bullet to take down a big animal from a handy, lightweight package that doesn’t take up much space.

Which one would I recommend? Personally the 450 Bushmaster, as it seems to be the most economical to shoot as 230gr .452″ pistol bullets for the 45 ACP are universal and cheap, and more premium hunting bullets are available as well. Additionally you get a few more trigger pulls per magazine if you go with the 450 Bushmaster over the 458 SOCOM (2 more in a 20 round mag and 3 more from a 30 round mag). In a situation where you want to save space, holding 26 shots in two 30 round STANAG magazines versus 20 shots in the same space makes a lot of sense to me. A “minimalist” AR build with a 16″ barrel would be light and handy (although recoil would be more than with a heavier build).

But no matter how I slice it, it seems that there is a very, very small niche market for these thumpers.


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