I've started to weighing everything, except primers, and have noted variations in weight. i sort everything now, so i get very uniform loads. different brass is thicker or thinner walled and will weigh out accordingly. and the thick brass will fill more with any specific powder charge as you found out ( as did i ), which could cause an issue depending on how deeply the bullet seats. i didnt mic the walls but i was surprised to find that the little difference in weight made such a difference in volume. i got a difference up to 2.4 grams total. but all my loads get sorted by total round weight and gets assigned a load number, i sure have bought alot of MTM cases, lol ...
glenn