I've had both the CZ 550 and the Model 70. I've still got the Model 70 grin One dimension that is different between the two actions is their respective depths. The 550 is a true magnum action, and is very deep, capable of handling as many as 6 375 cartridges down depending on how the magazine spring and follower are setup. The trade off for that is that the gun handles differently from most bolt actions, and carries differently in the hand. Not bad, just different. Frankly, I think the 550 is too big for the 375 and I prefer the Model 70 in that caliber.

Here's a pic that should illustrate what I'm talking about regarding action depth.

[Linked Image]