Here are a few pictures to help clarify dimensions given earlier.
While the
opening at the receiver rail is of similar length with both actions, not much else is.
Pre-64 model 70 rifles. Standard rifle is a .264, the magnum is a .300.
Just not willing to pull the scope on the .375 (already sighted in) this close to elk season, components to re-sight are to dear to come by nowadays!
First is photo of the standard action.
One of the cartridge at the point of being ejected - O.A.L. of 3.24", longer than the 3.12" ejection port -. Again, the rear of the case is under the bridge. Lots of space for proper ejection.
Next is the magnum. Two views of the action.
Radius front ring up toward the bullet cut out (not really necessary, especially with scope use) on top.
This radius extending from the receiver rail to the top of the ring is what gives proper tolerances for ejecting loaded rounds.
Angled corner on the bridge with a radius to the rear of the loading port.
This extra length of the loading port is why the magnums used a different and longer one piece scope base.
Cartridge - 3.57" - loaded into the magazine.
Last is the loaded round at the point of being ejected.
Again, lots of room for flawless operation.
If your acquaintance's rifle does not look like the latter photos, it is not an original .375 and furthermore, the rifle would not function properly on a standard action in that caliber.
Hope this helps to clarify the question.
JT