Is that the same as black tip?
Please refer to ATF for actual advice, but as far as I know, it is. The rationale may have been that 1) .06 is obsolete 2) .06 is not a naughty black plastic rifle caliber 3) Much surplus .06 is steel core anyway. I really don't know. One other theory is that AP .06 is a better and more stable long range target cartridge--in other words, a sporting round. Or if your oddly afflicted like myself, that some folks are trying to place things under the radar of loonies and criminals. Not a lot of drive bys and robberies with .06.