Pistol case bulges

I've only reloaded about 1,000 380 ACPs but not experienced that problem. (but I have reloaded many thousands of other semi-auto ammo). I would suspect somewhere in your method you are causing the bulge (have you measured the bulge, located where it is on the case and tried the plunk test?). Measure a case before starting and after each step to find out when it is happening and then you can determine why (too much flare, too much "crimp" etc.). Find out what's happening and you can fix those 10 cases, no sense in wasting brass...

I have never needed a "bulge buster" die and I have reloaded many, many "once fired" and range brass. My sizing dies have been sufficient with every case, caliber I've reloaded, although I have read of 40 S&W fired in a Glock has a bulge near the case head. I've read of some using a bulge buster for their guns that have tight chambers, but I haven't found any of my 9 semi-auto pistols to have this problem. Maybe some more familiar with one can help...

Another thought; .005" isn't very much and can be from bullet "base bulge". A resized case can be "tight" enough for the bullet to "expand" the tapered ID, some cases will experience more bulge depending on case wall thickness. If they plunk, shoot them...

Measure the case before and after each process to see where the bulge is happening.

The 'Bulge Buster' straightens the case walls before the sizing process. The flaring happens after sizing. If you are getting a bulge during flaring, then something else is happening. Maybe pushing the flaring die into the case too far and compressing the rim, causing a bulge/wrinkle? Pictures would help.

Reloaded ammo will often display strange shapes and bumps that factory ammo doesn't have.

The rule is: Let your barrel be your Go/No-Go gauge.