Guys,
XM193 is drying up because it was made as a one-time thing. When Alliant Techsystems (owner of Federal, CCI, Spear, RCBS, Ramline, Weaver, etc.) took over operation of Lake City from Winchester, there were a bunch of left-over components from Winchester's tenure there. Alliant apparently decided not to use those components for military ammo, but instead loaded them up for commercial sales and sold them off under their Federal brand name.
The ammo was loaded using 1-2 year old components, so the headstamps aren't 100% accurate (the ammo is technically newer than the headstamps indicate). With the exception of the lack of sealant on the later lots of ammo, the "XM193" is fully M193-spec ammo.
Again, this ammo was assembled with the intention of being sold on the civilian market, NOT to fulfill military contracts. There was some question whether the last lots would even be released, as there were apparently some people who were not happy about it being sold to normal folks.
Once it's gone, it will be GONE.
And because the prospects of getting more new-production M193 doesn't look all that great, I'd advise against shooting it all up for practice. Buy surplus stuff for that.
-Troy