44AMP : Do you mean crooked bullets bulging the case? Hmmm. Could be.
Oh, no "could be" about it. Straight walled case, slightly tipped bullet, run into the seater die can leave a bulge on one side of the brass. usually not enough to prevent chambering but visible to the eye. Does it always happen? No. But it can and has. Short generally blunt point (compared to rifle spitzers) bullets don't always completely "straighten up" on their way into the seater die. If they happen to lean just a bit to one side, the case can be bulged as the bullet is seated.
This is an operator function. Its up to the person loading to see to it that things are right, before and AS you work the handle.
I wonder if a Lyman "M" die can be located in stock?
People talk alot about needing to get a Lyman "M" die, and their two step expander is the best thing to use. I've never needed to get a Lyman M die, because they came with the Lyman die sets I use. Just looked at the expander die in my Lyman .44 Mag deluxe set and on the die body it says "Lyman Exp Die M1". The Exp die in my .357 set says the same thing. The "M" die body is just an open tube, never contacts the case at all, and the same M die body can use any and all the different caliber expanders. They are all the same in all the Lyman 3 die sets, the only difference is the caliber expander installed.
This is something that amuses me, when people go and get a die set, have issues and then solve them by getting a Lyman M die and the proper expander. I just think "should have bought the Lyman set in the first place". Use that money you saved buying Lee!
Most of my pistol dies are Lyman, because I bought most of them back in the early 70s when I lived in the north east and Lyman was what was on every shelf back then. A few RCBSs and the Lee products was the Lee Loader...
Likewise, it was mostly Rem or Win primers, not much CCI and Federal was rare.
Moved to the Pacific NW, just the opposite. RCBS was everywhere, Lyman was scarce and so were anything but CCI primers. This was decades before the Internet and very few of us did mail order buys, because what we needed was almost always stocked on the shelf at gunshops, and even dept stores.
I use my old Lyman dies for .38/357 .44 Mag and .45ACP. I have RCBS for 9mm and .45 Colt, and also for 44AMP and .45win mag. Have a few Lee dies, don't usually use them. Not because they don't do a good enough job, but because I don't like their features. Personal preference.
So, slightly tipped bullets can cause a bulge in a case. A BAD Crimp (too much crimp, or crimp in the wrong place) can cause a bulged case, a different bulge than what you get from a tipped bullet. Cases too long for your die adjustment can do the same thing (causing a bad crimp).
Until the OP comes back with more specific information, we're stuck here with conjecture.