It really depends on the barrel, but most shoot both 356 and 355 equally well. The thing you MUST look out for is shooting lead that doesn't seal in the barrel. If it doesn't, you will get gasses shearing down the sides of the lead bullet and leaving massive lead deposits in the barrel. FMJ's are not an issue as long as you are getting consistant accuracy.

BTW, if it's comp'ed don't shoot lead in it at all. It will fill the comp with lead deposits and cause a potentially dangerous situation.