If you look at the AA Fields, you can see a crimping line on each side of the pellet, which is hardly visible on the JSB. I presume they are using an older, and more worn, die to make the AA's. A while ago, I stood some Daystates up against the AA's, and I swear they were a tiny bit shorter, but I didn't put a micrometer on them. Other people say they are the same.
Gus