The "bulge" as you call it is a good thing. Of course, too much of a good thing can be bad, take cookies as an example!
All kidding aside, the reason your cases bulge is because the sizing die you have is small. Again, the added tension is a good thing. Case tension should hold the bullet in place and the crimp only aid in ignition, kinda.
Unless you are using the wrong size bullet, like .510" or something crazy like that, you are good to go. Lead bullets are usually .001" or more bigger than jacketed and will cause a more pronounced "bulge".
In my opinion, and I wish I could see some of your rounds, the bulge shouldn't be an issue. At least not from what I can see!