Happens to me that's why I use a trainer

You probably didnt give them actual ammo, but instead a debug item used for artillery, or something along those lines. The ammunition troops can use is:
-located on page 619 to 714
-near the middle of the page.

Make sure you give them rifle ammo rather than pistol ammo. Rifle ammo is the same picture, but rotated so that its horizontal rather than at a 45 degree angle.

(view screenshot for references)

https://cdn.discordapp.com/attachments/714844550304366603/723619110595985518/unknown.png

Did so, Ammo commited seppeku anyways.

Did you start a new game when 0. 3 was released