Berdan primed case pose many problem for the average reloader. First off the process of removing the primer is totally different,you either have to buy one of those RCBS decapping tools about $60 or make your own for punching through the old primer cup and popping it out.
Then you have the issue of actually finding small pistol berdan primes which to my knowledge nobody sells in the US anymore and haven't for many years and you can't simply just substitute a standard SP primer without reworking the primer pocket to convert it to use boxer primers. Berdan primers are also measured in millimeters and require different primers seating tools or modification of current available tools to seat properly and to the correct depth.
Bulgarian berdan primed brass is not the best quality brass to reload as it can suffer from age cracking issues. I know it's just doesn't seem normal to toss all that surplus brass,I have plenty of the stuff myself in 54r and I would be the first to want to save it for future use myself but the cost/time benefit makes it just not worth it when better options are available. I just toss it in the brass scrap bucket and sell mine to the local recyclers.
A better option wold be to just buy new brass https://www.starlinebrass.com/brass-cases/762x25-Tokarev-Brass/
small quantities of 100 can be purchase at most places that sell reloading components.
In a pinch you can reform 5.56/.223 brass or Win. 9mm Magnum cases into 7.62 x 25 brass it is a little extra work but not as much as trying to reload or convert berdan primed 7.62 x 25 cases.