Q. I'm concerned about roving packs of zombies driving automobiles after the end of the world as we know it. Since, as everyone knows, you have to make headshots to kill zombies, what ammo should I be using to defeat zombies in automobiles?
Without commenting on the wisdom of engaging roving packs of zombies without adult supervision, the best performing rounds, in terms of penetration of 6mm laminated front windscreen auto glass and other automobile structures, are probably the Federal Tactical 55 and 62 grain bonded JSP (LE223T1 and LE223T3).
Be aware, however, that these rounds, topped with Speer's Trophy Bonded Bear Claw bullet, are designed for penetration and generally do NOT fragment in CQB circumstances.
Unfortunately, Federal Tactical ammo is LEO-only, and while the Trophy Bonded Bear Claw bullet is available in hunting loads and as a reloading component in the 55gr weight, the 62gr version appears to be available only in the Federal Tactical line. TBBC bullets are also extremely expensive, as they are a high-end, low-volume-production item.
Federal Tactical JSP.