Re: The Expanse: Prop Weapons
A quick primer on molding for resin casting? I don't do that myself, but a search for 'molding tutorial' or 'silicone mold making' may point you in the right direction, either here or on Google.
Alternatively, you could ask some of the guys here who make a lot of molds & casts for some kind of beginners' website. Matsuo, Rick Ross (Doppelganger01), Kenny (KCPStudio), they're all notorious for high quality cast resin firearms. Be clear that you're not asking for their whole careers' worth of experience in 5 minutes, but a good 3rd party site for beginners (or whatever).
-MJ