well i finished the game and started a new game to have their skills...and this time i used the simulator more often so i could lvl up my weapons..now here's the thing when i start the mission i always get -15% on weapon lvl how come??? im in the mission where i met dennis and trying to escape from japan... i finished the enemy quickly but my rank is still 85% = gold because i always get -15% in weapon lvl even though its at 7...should i get a higher lvl of weapon??

here's the thing...
weapon lvl vs enemy lvl will determine the ranking
if your weapon lvl is high (like s or a) and ur enemies are
on a lower weapon grade like d or c of course you will be penalized coz you have the handicap of having higher weapon lvl..if you want to have a higher ranking then you should be the underdog..same weapon lvl with enemies or lower but of course the battle is harder

its ur option

Switch to weapons you don't normally use.