how does one transfer ammunition to a anti-tank gun

[DerSniffer]

select the ammo truck,

press "X"

go with the "eye - cursor" to the the anti tank gun, tank, artillery or whatever und press left mouse button

the ammo truck will drive through it and the both inventory windows will open.

now double left click on the correct ammunition sort - it ll be transfered to the gun.

sometimes you then have to shoot (especially panzerwerfers) to some place so that the vehicle know that it has to reload. when the reloading bar appears just cancel the shoot order.

i hope this will help.