The most general answer to the question is that shot shell payloads are based on weight, not volume. You'll notice that if you buy shells they indicate the weight of the payload (1 oz, 1 1/8 oz, etc) not volume (2 cubic centimeters, etc).
The ballistics of a shell are impacted by weight of the ejecta, not the volume, so you can't just substitute various payloads that take the same volume without impacting the ballistics.
Scott
The ballistics of a shell are impacted by weight of the ejecta, not the volume, so you can't just substitute various payloads that take the same volume without impacting the ballistics.
Scott