You admit you are uninitiated to the supply system, so perhaps you can accept an input: DODAC is the Federal Stock Class/Group plus the DODIC. Ammunition is FSC 13XX and the group for small arms ammo is “05.” I distributed the complete list of 13XX stock groups at SLICS to those I determined were interested. The DODAC helps identify ammo, in our interests, from similar codes for other commodities, which are also in the supply chain. The DODIC is a four digit alpha numeric code for an item PLUS any “similar” items coded in the supply system as a “suitable substitute.” For example, if a soldier on the battlefield, or his unit supply officer, requests the DODIC for a particular anti-armor 155mm projectile, the supply system will send him the fastest available projectile. Also, in a more basic form, if the troop runs back to the beachhead to pick up rifle ammo, by recognizing the DODIC, he can grab any box that meets his requirement, without sorting through a bunch of NSNs, packing methods, modifications to the round, etc. etc.
Yes, it is confusing, and I only worked with it for 30 years–