How do I update weight using Rules? I am creating a sampler pack of all my products. I have a product display with several node reference fields (not product reference) so that whenever a new product is added, that reference field is updated.

I have Rules set up to automatically price those selections (each selection has a different price).

Now I'm trying to use Rules to update that line item's weight (for use with Commerce UPS). However, I can't seem to find a way to update the weight. Is this possible in Rules? Or am I going about this in the wrong way?
You'll have to add a condition to your Rule.

Make an "Entity has field" condition that checks for your weight field.

You'll now be able to use that data value.