If you look closely at the current Model 70 actions, you will find they are all the exact same 'external' length. They are machined differently so the ejection ports and bolt throw vary. It an ironic twist, this results in a 243 action that is heavier than a 300 win mag action. The 243 has less steel removed from the same size raw stock as the 30-06.
Now a company like CZ has 4 different size actions where they are a actually proportioned to the round. A short for the 223, a medium for the 243, a standard for the 30-06 and a magnum that will handle the 505 gibbs. This is also true of sako, who has at least 4 true sizes.
I belive Ruger has two true sizes. Real size differences. The 223 is chambered in a 243 size action. They dont make a 458Lott size since they dropped the big RSM action.
You could say the M70 is machined 3 or 4 different ways using the same action blank. One size, but; different actions, no spacers in the magazine. It makes for a great 375H&H not so much for a light woods rifle in any medium length ctg. Kimber does a great job of sizing the actions to the round. The Remington Model 7 is sized "just right" for the 308 family. The later two are sized in both diameter and length.