So I finally got round to building the new Contemptor Dreadnought that came with the Age of Darkness "starter" box for the Horus Heresy. It's a really nice model and easy enough to build with the added bonus that I am 99% sure that who ever did the design for the weapons did it with magnetization in mind.
All you need is some 4mm x 1mm magnets and you're good to go. Oh, also some superglue. but be careful with that, remember when it comes to superglue, less is better.
***** AMAZON AFFILIATE LINK FOR MAGNETS
4mm x 1mm magnets https://geni.us/DRRP