Weapons won't realod to full ammo count.

The one round short your seeing is not a bug but actually a normal function of all firearms whether in game or real life. For example When you spawn you start off with 31 rounds this amount is 30 rounds in the magazine and one in the chamber or known as 30+1. When you reload your magazines are only going hold 30 so you’ll have one less round unless you reload again to have 30+1. Some guns firearms can't be loaded with +1 by design.