Al and greydog are right. The .004" is an estimate, but in reality it all depends on the brass, and even that varies. I once chambered an old barrel for fireforming, used the .004", and had 100 new cases to fireform prior to a prairie dog hunt. Most closed with feel, so one would expect. Some closed without a feel and some I had to push hard to close the bolt. Same lot of brass. Next time I will go .006" and seat a bullet long as insurance.
BTW, a 6PPC does the same thing. A chamber at zero headspace won't quite close on a 220 Russian case, unless you run it in a sizing die to slightly push the shoulder. If you chamber .002" deep, they close fine.
