Starline 458 SOCOM Brass Cases (Large Pistol Primer) The SOCOM is an awesome cartridge that is basically a long 50AE (O.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 its claim to fame is in the AR-15 platform. This case is designed for use in correct US manufactured .458 SOCOM firearms, dies, and ammunition; not the improper dimensions provided in the CIP cartridge/chamber print. O.A.L.: 1.569-1.576 100 count by weight