When you find a spidertron remains, you get all the starting basic techs INCLUDING the gun "crapthrower". Yet when you then pick up any other remnant, you get a message referring to you unlocking the gun, so it seems that there is missing a tech unlock that should give you the gun after grabbing some other scrap

I think I understand. It is not a missing technology, but that the hint text plays additionally on a confusing remnant. I will address this in the next release.

It is now live. The new text for the spidertron has that second line about the gun play some time after you mine it, and it says:
"You can't stop thinking about that first spidertron wreck. You are inspired to build a large gun ...."

Thank you for your feedback.

No problem, it's a great mod. I just wonder if factorissmo works with the planet by also changing how the belts are oriented or not. Will check just not right now