Lead Shrinkage?

[korny351]

I've been reloading off and on for nearly 40 years. Decided to try and clean up some of my old stock. I found some old (30 years) Hornady 158gr. 38 cal. RNL bullets that I used to buy in bulk. Figured I'd just load them up for plinking ammo. As I was loading I noticed that some of them seemed to seat with almost no pressure whatsoever. Went back through what I had loaded and found some that would push back into the case with just finger pressure. Using my calipers I measured diameters from .3535 to .3575 with the bulk of them coming in at around .3550. I double checked the weight, just in case I had found some 9mm in error, but they came in at 158gr. Broke down the bad ammo I had found and just tossed the rest of the bullets.

Is it possible that over the years the lead has shrunk? Maybe due to cycles of heating and cooling? They had been stored either in an unheated basement in Chicago or in the garage or reloading shed in northern Ca.

I just don't remember having this issue when I was loading them back in the day. Or was Hornady's QC that bad and I was just oblivious?