Quote Originally Posted by phuonglop12a2 View Post
How is Weapon bonus ( ATK increase with damage received) work? Should I MLB it?
According to Jap Wiki, the weapon skill level doesn't change. It's still 0.5% per skill level, regardless of your current HP.

The base changes depending on your HP, however. 0% at full health, 4% at 80% HP (so more than SR Assault weapons), 6% at 70% HP (so equal to SSR weapons). At best, at 5% HP it is 19%.

The Union weapons are well worth it, since they're only worse at full health. And even then, they're not that bad.