Hello and welcome! It is very important to determine if your bolt is ground and if so how much has been removed because this will give you a false bolt gap reading. I suggest that you go to Militaryfirearm you will find all of the info you need about the Cetme there including the proper bolt length. They will walk you through the whole process. If your bolt is ground you do not have to replace it as long as you know how much has been removed and you account for it when measuring bolt gap. Insuffecent bolt gap can result in a kaboom so it is very important to know what you are dealing with.