I have 900 30-06 cases that I planned on resizing to 7.7 jap. After cleaning I noticed 2/3 of them have a bulge just above the web. My dad and I reloaded for this rifle 20 years ago and I just inherited it. We resized 100 30-06 cases back then and I noticed some of them have the same bulge. I also have 100 norma 7.7 brass that i believe are once fired and about 10 have bulges too. I bent a piece of wire and can not find any thin spots in the walls. Is this common for 30-06 brass? The 30-06 cases are at least 20 years old and I dont know the history of them. any help?