It works like this:

SEE_THRU = Is material see through (glass for example) SHOOT_THRU = Are you able to shoot through material. SHOOT_THRU_FX = Should effects (dust/smoke etc) be shown when bullet goes through material NO_DECAL = Do not show a decal (bullet hole etc) on the material when bullet goes through etc

1 = Yes 0 = No

For most materials you want bullets to penetrate your data entry will be:

0 1 1 0

Meaning the material is not see through but can be shot through & will display effects & decal on bullet penetration.

Note: I seem to remember this approach causing me trouble getting explosive machinegun fire (like the Savage/Hunter's main gun etc) to explode on contact so I would test that out right after you make the changes to 'CAR_METAL' etc to make sure it is still working correctly. Jump in the Savage/Hunter etc & try shooting down another helicopter (or a vehicle with nothing behind it) to make sure the main gun's bullets explode on contact etc