HSM Ammunition Starline Pistol Brass Unprimed Cases 458 SOCOM Caliber 50 Per Bag. A.L. of 1.575") with a rebated .308 style head configuration necked down to utilize a .458" diameter projectiles. It has been chambered in some bolt guns but it's claim to fame is in the AR-15 platform. Specifications for Starline Brass Unprimed Cases Handgun 458 SOCOM: Manufacturer: HSM Ammunition Gun Type: Pistol Caliber: .458 SOCOM Primed: No Quantity: 50 Fabric/Material: Brass Package Contents: Starline Brass Unprimed Cases Handgun 458 SOCOM