Paul, right now ammo and firearms are in high demand and low stock. Manufacturers are focusing on producing their most sold products unfortunately like 9mm, 223, 22lr, and so on. For my harder to find calibers I use a website called ammoseek. Just Google ammoseek and type in the caliber you're looking for and if any websites have any in stock it'll find it. I've already checked and plenty of options. Hope this helps.

Ammoseek is your answer...

Paul, 30 Carbine ammo can be found in stock here Sir : -- https://ammoseek.com/ammo/30-carbine

As this is a community forum, not sure if you will get the answer you are looking for here, however, it seems from research I've conducted regarding this particular round that ammo manufacturers tend to decrease production of the 30 Carbine during ammo shortages to use the materials to meet the higher demand of more common rounds. As the ammo shortage is slowing, production should catch back up in 30 Carbine soon.