A lot also depends on if the unit maintains a partial load on its heavy vehicles, roe example, in the 1980s, tank units in Germany, forward of Ansbach, would maintain a load of 40 rounds of main gun ammo, usually 25 APDS and 15 HEAT. When an alert was sounded, the plan (snicker) was to move out to our ready positions, where the ASP would bring the semis with the rest of the ammo load to us. Since we had M60A3s, our WP and HEP were stored on the trailers, following the switch to M1s, everything was switched to APDS/HEAT only. Since.we were armored cavalry, we also had a selection of land mines, cratering charges and demolition gear, as well as TOWs, Dragons and LAWs.
For the units stationed west of Ansbach, they depended on the ASPs for all of their ammunition. Although I have heard that this policy was changed whenever tensions increased.
Pretty much the only units that I am aware of that had small arms ammo readily available were the units equipped with Pershing, the forward SAM batteries.
Going stateside...trust soldiers with live ammo? Only on the firing ranges! The ASPs were protected by armed civilian security.
As the tee shirt says, "They don't trust us with ammo, but they want us to be able to run really fast..."