In case this wasn't obvious, the higher a weapon's level in Raid mode, the better it is. There is one important difference for level 100 weapons however, in that these weapons can be upgraded past their original limits.
When you select a level 100 weapon you'll notice an extra option that's usually greyed out called "Upgrading Beyond Limits". In exchange for lots (and I mean lots) of gold, you can push some of the stats to new highs.
Keep in mind the max number of upgrades is 30, but try not think about how much it'll cost you to get that far or you might get cold feet...
Upgrading's expensive, but if you want the best you better be ready to pay for it!
Date: Jun 12 2015