I have custom weapons in the map, and my starting gun is the Mauser but when I buy a box weapon, I only have that 1 gun. The only way to get two is to buy a wall weapon first. Is there anyone to fix this?

In _zombiemode_weapons.gsc, search for zombie_colt and replace it with Mausers weaponfile name:

if( primaryWeapons[i] == "zombie_colt")