What happens to lead:tin:antimony bullets' size as they age?

[Naphtali]

Two things of which I am aware that result with casting bullets when hardening agents such as arsenic and antimony are included in a lead:tin mixture. One is - well - bullets are harder. The other is bullets are slightly larger as dropped than were hardening agents omitted.

If bullets are stored at room temperature, I believe that the hardness may deteriorate after several years have passed. What happens to the slight enlargement? That is, does the bullet shrink as it reverts to the hardness of lead:tin mixture, or will it retain whatever dimensions it has as dropped?

[243winxb]

After sizing, diameter remains the same. I am not running down into the basement to check my test samples again, as they never have changed diameter sitting there in many years.

[44man]

My boolits grow. I lube and size my .475 boolit to .476" and if they sit they will reach .478". Smaller will not grow as much. You might not be able to see it with a 30 caliber. Maybe .0005".
They will soften over time but it could be years. I don't think they will shrink, never have them around long enough!

[JeffinNZ]

Given that proper sizing doesn't remove material but displaces metal (the bullet gets fractionally longer) it feasible that as the bullet 'relaxes' the girth might expand a tiny amount again.

[gwpercle]

One thing I did notice after casting a bunch of RN 9mm boolits of 50% COWW , 49 % lead and 1 % tin, was that the boolits I sized & lubed the same day as cast , with a flat nose punch, left a small flat spot on top of the boolit. Boolits sized and lubed just one week later had no flat spot, same sizer and flat punch....they had hardened just enough to resist the flat punch leaving a flat spot on top .
Had never noticed that before....very interesting ! I sort of liked the little meplate on them.

Gary