In The Field
Much of the research on the capabilities of big-bore AR-15 rounds like the .458 SOCOM concentrate in the area of subsonic (1,050 fps and lower velocities) and suppressed loads. That's the where and why of the super-heavy 450-, 500- and 600-grain bullets. I would imagine folks hiking, fishing or living in big bear country might also opt for the heavy weights. The Coast Guard uses them to put big holes in bad boats, but for hunters, bullets in the 250 to 350-grain range will be the most useful.
A 300-grain, well-constructed bullet moving at about 2,000 fps is 150- to 200-yard bad medicine for just about anything, including bear and moose. It's certainly big enough for elk, and there's not a deer alive that will walk away from a solid hit. The energy of such a combination is 2,400 foot-pounds at the muzzle and, within 100 yards, it doesn't weaken much. That puts it squarely in the territory of the modern .45-70 or .450 Marlin, and it will do anything those rounds will do. The mighty .458 Winchester Magnum only bumps 2,100 fps with the 300-grainers.
Of course, all of these other cases soon outperform the .458 SOCOM as bullet weights get heavier since they have the case capacity to push the 400-, 500- and even 600-grain heavy weights much faster. With those weights, you don't have enough powder capacity in the .458. Velocity drops fast, and they slow way down and go subsonic, precisely as the design required.
Reloading
Dies are available from Hornady, Lee, CH, and soon will be available from Redding. Bullet choices are vast with Nosler, Hornady, Barnes, Speer, Woodleigh, Swift, A-Frame, Sierra, and Lost River all offering great bullets in .458 from 250 to 600 grains. Both Remington and Winchester produce bulk bullets in .458. Whatever your preference, bullets won't be a problem, nor will the large pistol primers this case uses. A wide diversity of powders have also proven accurate in the SOCOM from Hodgdon's Lil Gun to 4198. It's a very easy case to load for, as long as your dies don't push the minimal shoulder back.
The one component that is currently in short supply is cases. They are made by Starline and available from them, Midway or Graf & Sons, but due to a fast-rising demand and the general shortages we've experienced since the last election, there are currently brass shortages, and orders are going on backorder. Both Starline and CorBon assure me that supplies should increase by the time this goes to press.
At The Bench
My test rifle is a Rock River A4 upper and lower, flat top receiver with a 3-9 scope mounted on medium rings. In my opinion, 200 yards is this rifle's practical hunting range. Good shooters will no doubt stretch that a lot, with high BC bullets, but big game is way different than steel gongs. After the accuracy testing, the more precise, higher-magnification scope will be replaced with either a 3X or 4X ACOG or a red dot for faster target acquisition. The rifle is fitted with the Rock River match trigger, but no other modifications are made — pretty much stock as delivered by Rock River Arms.
Rock River offers either complete rifles or just uppers in .458. As of now, they only offer a 16-inch chrome barrel with a flash hider (good to protect the crown, even if you're not concerned about flash), and no front sight. I wish an 18- or 20-inch barrel were available. It would quiet things down quite a bit and probably add a bit more velocity.
The Rock River line is known for quality, and this rifle is no exception. But were I to have their ear as to the design, it would have an elevated optical platform (EOP) to get the scope up a bit higher, and a real recoil pad!
For all the myriad of aftermarket parts available for ARs, volumes of catalogues or aftermarket goodies, no one offers an A2-style buttstock with a real recoil pad. The standard hard plate, more than adequate for the .223, is a real meat grinder with the .458. There is an ACE skeletonized buttstock that comes with a ½- or 1-inch rubber pad, and my order went in to Brownells immediately after doing the testing. I have it on good authority that DPMS will be offering an A2 buttstock with a real recoil pad in the near future. Stay tuned.
Corbon factory loads with what appears to be a 300-grain Sierra FBHP were the only loads I had available. Dies ordered from Hornady have not yet arrived. Pulling the bullet showed a powder charge of 29.2 grains of a flake powder that filled the case to about 2⁄3 capacity. A lot of powder room was left in that case. I'm anxious to work up reloads, but you can't hotrod AR loads. They must be loaded to a narrow pressure. Velocity range or timing goes to pot and reliability suffers. Hot loads are more trouble than they're worth. Over the chronograph, velocity 15 feet from the muzzle measured 1,927 fps with a deviation of 18 fps — very consistent performance — and it showed on the target.
A bit on the results before I go on. If you're like me you soon get pretty suspicious of gun writers who seem to get sub 1-inch, 100-yard groups from everything they shoot. Maybe they have a magic trigger finger. That's not the way things are in the real world.
This factory load from this unmodified rifle never exceeded 2 inches at 100 yards, with most groups holding at 11⁄2 inches and several sub 1-inch clusters in the mix. That is extraordinary accuracy from an unmodified semi-auto rifle. I am not surprised. Short cases moving heavy projectiles at moderate velocities are usually capable of excellent accuracy, but this is exceptional.
I fired about 50 rounds downrange, all fed from standard 10-round .223 magazines. The .223 magazine only hold three rounds of .458, making it legal for hunting where magazines are limited to five rounds or less. There was never a failure to feed, it never jammed, or gave me a problem of any sort. This AR design likes this load. Other loads for reloaders are available from the Teppo Jutsu Web site, and a lively reloading discussion is always underway at the .458 SOCOM Forum.
Bottom Line
Thoughts of AR-15s automatically lean towards their most familiar load, the versatile.223, and the expansion to .204, 6.8, .30 Remington AR, and the like have given it solid deer and antelope hunting credentials.
No one will argue the effectiveness of those cartridges on deer, but for bear, elk, and moose, the job had to be left to its bigger, heavier brother, the AR10 — where the mega rounds are found. No more. With the introduction of the .458 SOCOM, the trim AR-15 is more than tough enough for the big guys.
Contacts: .458 SOCOM
Ammunition
www.SBRammunition.com
Cor Bon
www.ReedsAmmo.com
.458 Rifle or Upper
www.RockRiverArms.com
www.TeppoJutsu.com
.458 Forum
www.458socomforums.com
Brass
www.Grafs.com
www.StarlineBrass.com
www.MidwayUSA.com
Padded Buttstock
(and virtually anything else you'd ever need for an AR, including instructions on how to build one):
www.Brownells.com
