The 64 action is lot more fragile compare to 54 action and less air tight head space and got
Lot more vibration when fired,the 54 has a lot better trigger mechanism
Anschutz usually utilize their low end barrels of the line for the 64 actions
I actually own both actions and grouping are more tight with the 54 in comparison
The 64 bolt it self are made from casting hardened at one end
and sometime they break in 2 pieces.
There are several misconceptions in this post.
First, the Anschutz 5098 trigger in many 64s is at least as good as, if not better than, the 5096 and 5109 triggers on many 54-action sporters, and can actually be adjusted down to a lower weight-of-pull.
Second, as grauhanen notes, it's well-known that Anschutz puts the same barrels on their 64s as go on the 54s. The differences are in the actions, not the barrels.
Third, there will be no difference between the 64s and 54s in terms of headspace. Why should there be? Headspace doesn't depend on the action, but rather on the fitting of the barrel to the action, and we can be pretty sure that Anschutz gets the headspace right on all of their models.
As for vibration, that's the first I've heard of that. It's true that the 64-action rifles tend to be lighter than the 54s (and the 64 action itself is lighter than a 54), so perhaps they move a little more on the bags when shooting from the bench. Nonetheless, a lot of shooters have shot some pretty impressive groups with their 64-action Anschutzes. From what I've read, any differences in overall accuracy between the 64 and 54 are very, very small. As for fragility, the hundreds of thousands of 64s used over the years in shooting programs worldwide, with tens of thousands of rounds fired through them, would attest to their durability. The Anschutz 64 action is a very good one--far better than most competitors--and any 64-action rifle, if cared for properly, should last several lifetimes.