ONE 5.56 MM ELP HBMM HOLLOW BASE MAGNETIC MAMA CARTRIDGE. HEADSTAMP WINCHESTER 223 REM OR W C C 1 3. HBMM (Hollow Base Magnetic Momma) a 47 GR. Hollow Base composite projectile uses old-school tungsten core and Frictionless High-Speed flow groove technology providing that little added penetration and the ability to accept that extra powder charge up it’s Axx. Because of specialized Product Engineering this projectile is designed with a little more weight and longer lean profile so the core pushes through with the housing on less solid obsticals and peals off when striking more solid obsticals to control those Varmints and Predator.