Garand barrels in 7.62x51 nato

[Cosine26]

I do not doubt the above information that the 7.62/308 M1 requires a larger gas port than does the 30-06 M1 but my question is WHY? It would logically seem to me that both the 7.62 and the 30-06 develop approximately the same chamber pressure (~50K PSI) and the bore length from the chamber to the port is approximately the same (though the 7.62 case is approximately ¼ inch shorter than the 30-06). Perhaps someone can tell me why the larger port is required for the 7.62/308.
Just curious.

Information

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[campperrykid]

In theory , the smaller volume of gas produced by a smaller powder charge in a smaller case -- forced thru a same diameter ( but slightly longer ) rifled part of the bore produces lower port pressure .
In my experience the Italian Typo 2 conversions do not have and do not need the larger gas port , It is possible that the conversions have slightly greater volume in the gas cylinder when the rod/piston is at rest. The distance from case mouth to gas port may also be a factor.