[R0]

Here is what you can use:

pawn Код:

new currentammo[MAX_PLAYERS];
new gunammo[MAX_PLAYERS];

public OnPlayerChangeWeapon(playerid, oldweapon, newweapon)
{
    if(newweapon == 27) // taking spas for example
    {
        currentammo[playerid] = 7;
        gunammo[playerid] = GetPlayerAmmo(playerid)-currentammo[playerid];
    }
    return 1;
}

and:

pawn Код:

public OnPlayerWeaponShot(playerid, weaponid, hittype, hitid, Float:fX, Float:fY, Float:fZ)
{
    if(weaponid == 27)
    {
        currentammo[playerid] -= 1;
    }
    return 1;
}