Who handles ammo? Is it an S4 or an S3 function to request and draw Ammo?

It is handled by the S3. First you have to realize the ammo is forcasted in a system called the Total Ammunition Management Information System (TAMIS). The way we figure this out is by forecasting the training required to meet our unit training plan. Once the BN the requests the ammo from the S3 shop forecast is approved and the ammo is allotted. The ammo for each training event is specified in the Standards in Weapons Training (STRAC), DA PAM 350–38. Once all of this lines up its ready for the unit to pick up.

When it comes to handling ammo, it's typically more of an S3 function to request and draw it. S4 might be involved in the logistical side of things, like making sure there's enough supply and organizing the distribution, but the actual request and draw usually fall under S3. As for where to get your ammo, sites like https://bulkmunitions.com/ could be a good option. I've found that having a reliable source for ammo is key, especially if you're going to the range regularly or need it for training exercises. It's all about being prepared and having what you need when you need it, right? So, whether you're in the field or at the range, having a good supply of ammo is essential.

FM6.0 CH2
Training
2-49. G-3
 Conductingtrainingwithinthecommand.
 Preparingtrainingguidanceforthecommander’sapproval.
 Identifyingtrainingrequirements,basedontheunitmissionessentialtasklistandtrainingstatus.
 Determiningrequirementsforandallocationoftrainingresources.
 Organizing and conducting internal schools, and obtaining and allocating quotas for external
schools.
 Conductingtraininginspections,tests,andevaluations.
 Maintainingtheunitreadinessstatusofeachunitinthecommand.
 Compilingtrainingrecordsandreports.

Look in AR350-1, DA PAm 350-85 and AR5-31. Are you FORSCOM or RC? The FORSCOM reg spells it out