C_B -
I just compared the bolts from my 77/22 LR and my son's 77/22 VMBZ. They appear identical except the rim recess on front of the bolt measures very slightly larger (less than .010") on the 22Mag bolt, and the extractors appear to have a little more "beef" on the mag bolt.
Tried 4 different brands of ammo (Winchester, PMC. Federal, and CCI) and none would go into the recess of my 22LR bolt, diameter of rims were just slightly too large. Everything else, length, diameter, etc., appear the same. Regards,