Everyone that reloads 30-30 owns a crimp die. It is found in the seating die in any common two die set. A bulged shoulder does sound like a misadjusted seating die set to crimp too much. Very possible, especially if case length varies.
@Mike Britton I did the same thing the first time I loaded 32 Remington with a two die set. The seating die was adjusted for too much crimp and shoulder collapsed (bulged). I find it easier to back off the crimp adjustment and use the die only to seat the bullet. I use a Lee FCD to crimp in separate operation.
My second issue was resizing the brass too much. I followed the directions for setting up the resizing die and it ended up being too aggressive and bumping the shoulder back too far. 32 Remington cartridges' are head spaced off the shoulder. I had a 50% failure rate with what I thought at the time were soft primer strikes.
One more reason to toss the 10 rounds that are wrong. I will pull the bullets, feed the powder to the house plants and shoot WD40 into the brass to kill the primers.
I'm not going to stress over 10 rounds.....