I wish the Remington 5mm rimfire magnum had caught on. Those who bought one have a hard time finding ammo. I think Remington does do run of the ammo every few years.
Never can figure ahead on this stuff sometimes. Guess they made a LOT of T/C Contender Barrels for that round also.
Aguila just dropped a batch of 5mm on the market; check Midway and the other usual sources.