Bolt gap tolerance is .004~.020" with the bolt fully closed with the hammer resting on the back of the bolt (dry fired).
There are a number of things that need to be checked to properly diagnose the problem. Century sold a lot of these rifles with the back of the bolt head ground short in order to give a completely false bolt gap and yours could actually be coming to rest on the cocking handle rather than the back of the barrel, with a true bolt gap of zero.
Rather than going through the long list of items that you need to check I would point you to the militaryfirearm.com site as all of the information, photos, and online help is already in place for curing the ills of these rifles. We get about one a week similar to yours. Sometimes it's an easy fix, sometimes not. Militaryfirearm is an offshoot of the old cetmerifles forum.