The 458 HAM'R is a big bore, centerfire rifle cartridge, intended for use as a hunting round in AR-15/AR-10 hybrid-style rifles. It was developed as a Thumper Round by Bill Wilson of Wilson Combat because he felt the 458 SOCOM was a good cartridge but could be better.
Wilson is a renowned big game hunter and, while he liked it, he found that hunting with the 458 SOCOM was lacking at 200 yards because the bullets failed to expand correctly. He witnessed this on two separate hunts involving an elk and a zebra at that range. Wilson modified the existing 458 SOCOM by moving the shoulder forward by 0.4 inches to give the round more powder capacity and ultimately much more velocity and thrust for proper expansion of a 300-grain bullet at 200 yards. The cartridge is loaded with a small rifle primer so that the cartridge case can handle the additional pressure without the primer backing out. Brass is made by Starline.
The 458 HAM’R operates at higher pressures than a 458 SOCOM giving the shooter more range with a much flatter trajectory. A 458 SOCOM has a maximum pressure rating of 35,000 psi whereas the 458 HAM'R can generate as much as 46,000 psi. This is why a 458 HAM’R build requires the AR-10 style upper receiver and components such as the bolt and barrel extension, so it can stand up to those pressures where the same components as an AR-15 will catastrophically fail.
Due to this increased pressure, 458 HAM'R requires an AR-10 (308 Winchester) style upper, bolt and barrel extension. Wilson Combat offers a factory rifle chambered in 458 HAM’R called the WC-12, which is a hybrid of an AR-10 and AR-15, taking the magazines of the latter. However, one of these rifles can be built on an AR-10 lower receiver that accepts AR-15-type magazines.
The 458 HAM’R has the same overall length as a 458 SOCOM for use in AR-15 magazines but like the 458 SOCOM, these magazines will need to be modified so that the rifle will feed and function reliably. The fact that the shoulder of the 458 HAM’R is set 0.4 inches forward of the 458 SOCOM will prevent a 458 HAM’R round from chambering in a firearm intended for 458 SOCOM.
As a hunting round, it can be used on medium and large game such as deer, bear, wild pig, and elk out to 300 yards. It definitely has the potential to be an effective dangerous game cartridge against mountain lions, leopards, or cape buffalo with the right projectiles.
Due to the ballistics of the 458 HAM’R cartridge, it could easily find a role within the military and law enforcement communities as a tactical round for close quarters combat (CQC) if magazine capacity is not an issue. Because of the large size of the round, it drives magazine capacity down by about 1/3. A modified 20-round AR-15 magazine will hold six rounds of 458 HAM’R whereas a 30-round magazine will only hold 10. Still, the energy and penetration offered at close range make it worth this trade-off.
Keep in mind that the 458 HAM’R with a 300-grain bullet still delivers more energy at 300 yards than a 5.56 NATO round with a 62-grain bullet delivers at the muzzle. Due to the bullet’s weight, it will lose energy and velocity rapidly past 300 yards. Like the 458 SOCOM, a shooter must take this into consideration for a humane and successful hunt.
The 458 HAM'R was designed from start to finish as the hardest-hitting, most powerful round that would fit in an AR platform carbine. It easily exceeds the ballistics of other Thumper Rounds such as the 450 Bushmaster, 458 SOCOM, and 50 Beowulf. The 458 HAM’R offers a little bit more recoil than a 458 SOCOM. It has been compared to firing a 12 gauge 3.5-inch shotgun round.
The AR10-type bolt and barrel extension allow this relatively new round to handle a maximum pressure of 46,000 psi and still exceed 3,000-foot pounds of energy from a short 18-inch rifle-length barrel. The 458 HAM'R is for all intents and purposes a 458 SOCOM MAGNUM.
Wilson chose the name for the 458 HAM’R much like he chose the name for the 300 HAM’R; it is brutally effective on wild hogs. A full rifle length barrel is recommended in order to maintain the increased velocity and flatter trajectory of the round. A shorter barrel will only give the shooter the same ballistics as a 458 SOCOM.
SBR Ammunition offers a variety of factory loads in the 458 HAM’R