corrupt baked textures?

So I’ve been trying to bake a high-res texture I created for use on a low poly model. I select the high poly model and then shift and right click the low poly model, set the Bake Type to normal, checked Selected to Active, currently have the margin set 8 px and the Ray Distance is currently set to .3. Everytime I try to bake the resulting textures don’t seem to be as high-res and for some reason, have patches of rainbow colours splattered around. Does anyone have any idea on how to fix this, or am I just mistaken with it not being high-res?