Tier 0,9 does not mean that you have maxed your weapon,it only tel you that your opalo can upgrade to tier 1,0 and over uo to tier 10,0.
Opalo is maxed when hit and damage SIB is "not any more"
As for upgrade Breer M1a or you can try to max CB5 it does one more damage than opalo.
A101 fits for...