All types of armor that comes with the stock game absorbs bullets with their high gib wound limit. To improve realism, I think that some of the armor such as riot shield, and helmet should deflect low powered bullets such as those fired from pistol, smg, and shotgun, and grenade shrapnel. while things that might be heavily armored such as the dropships' doors should deflect anything other than sniper rifles or cannons.

If you raised the structuralintegrity of the material used or used a material with higher structural integrity it would do just that...

I'm gonna use Mega Metal for the lightly armored stuff and a new material with integrity of around 400 for heavily armored stuff.

Also, I found that Engine B of Dummy dropship can't be hit by projectiles because it has "GetsHitByMOs = 0"

Wow, that engine does have GetsHitByMOs = 0. Thats why that darn little thing was so hard to hit .

But yeah, mega metal will deflect SMG/Dreadnought caliber bullets. It's not totally realistic for armor to totally resist a bullet, but it's is pretty fun to advance through an entire fusillade of bullets having them all bounce off. Mod it in if that's your preference.

Now I hate that dropship engine btw.

THAT'S why I can't hit them engines...
Oops.