Ahhh grasshopper. You are in need of a rulebook. www.idpa.com has a link to it.

Here is the deal. Empty mags are worthless and can be tossed on the ground. Mags with ammo left in them are required to be retained somehow, just in case you need that ammo later.

So, if you want to do a reload and the mag still has ammo in it, you have a choice. Tac reload or RWR.

If you have a jam, you can ditch the possibly bad mag and ammo.

(in IPSC you just reload whenever you want and do whatever you want with the mag.)