That's the price you have to pay when you want to play around with older cartridges that are on the cusp of being obsolete. I'm in the same boat with my .250 Savage, but it's not like I'm out shooting it all the time to where I need to load up lots of ammo or will be reloading smaller batches frequently. When I want to do a lot of shooting I bring rifle better suited for that like a 22LR or .223 or .308.

You rechamber a 99 from 300 to 308 though you'll ruin any value it has.