SpudFiles

how will differant weights of ammo affect a shot from a half inch marble gun that runs at 180 psi. will it do more damage using a steal marble or a light weight slingshot ammo if there both the same size whitch will do more damage. since the slingshot ammo marbles go fast but im thinking of buying steal ones will they do more damage?

In your case steel marbles would be better. Thats not always true though because a GB will do more damage then a spud even though a spud weighs more. I think the word you searching for is density.

When I shoot 1" shooter type marbles from my 1" barrel they bounce off of steel targets. but when I use large steel nuts and bolts . they go all the way through. Lead chunks will sometimes go through but not as easily as steel ammo.

One might point out that as well as being harder, the steel projectiles are heavier. Heavier objects work better internaly - they lower how important ineffishincies in your valve system are, and they don't go near the speed of sound. This means that they'll be given more energy.
And being heavier, they'll have better external preformance, keeping more of their (larger) starting energy.