First was 30 Herrett. Then 7-30 Waters from 30-30, 6.5x55 Swedish from 270, 284 Win. to 7.5 Swiss, 30-06 to 7.7 Jap and 8mm Mauser. Also turned some 22 Remington mag into 223 Remington during shortage. And 308 to 300 Savage.
I picked up a lot of used rifles in the last decade just when reloading components were getting scarce. Started buying Redding form and trim dies when I could.
My biggest use of conversion is making 6x47MM Lapua from 6.5x47 Lapua for my 'J' word target rifle.