sabresfaninthesouth
Lifelong Cynic
I was wondering about that too. But before he said he would go, Beth also volunteered. Maybe after Rick and the gang talked her out of going (for obvious reasons) Axel changed his mind. Or maybe they figured he'd be about as useless as her on that trip.
I was thinking it was as simple as the fact that they could only take 4 people.
Michonne has to go because she's showing the way. Daryl and Rick are obvious. That really only leaves one spot in the car if they're going to have room for Glen and Maggie on the way back.
Given the choice between Oscar or Axel in a fight - namely how much bigger and stronger Oscar is - it seems an easy choice.