Yeah, emcon put you on the right direction. Disassembling the bolt to get all of the cosmo out is pretty important. If it's too gummed up you could possibly break the firing pin. If it does break, the only way to get a replacement these days is to buy a firing pin for a K98 and have someone to fabricate it to fit the shorter yugo bolt.
That coupled with the fact that a lot of the surplus 8mm mauser ammo does indeed have hard primers.
One last thing, welcome aboard sir
