a 30-06 would not chamber in a 25-06 unles there was something really wrong with the chamber.
By measurement I can not make either a .308 or 30-06 fit in a 25-06 chamber.
The overall length on some match grade Black Hills 175 grain Boattail Hollowpoint .308 I have (chosen for it's presumed precision) is right at 2 13/16 inches. If the loading manual case size is correct a 25-06 case is just shy of 2 8/16 inches ( 2 31/64"). If even a small projectile (87 grains)is attached it would almost certainly consume another 8/16 of chamber. Which means the .308 would be at least 4/16 inch too short for the firing pin to reach it.
It gets even worse if you assume shoulder or case mouth or ogive "pinch".
With a 30-06 the case is at least more or less the right size, but you still have to cram the projectile into the case when you close the bolt ( a red flag if ever there was one)
Seems to me a small miracle the gun fired at all, let alone exploded.
Just saying.
I will closely examine the next 25-06 I run across in my travels. Maybe some reloaders or gunsmiths can explain it to me.