First Marine is Lieutenant Cyprian - Simple head swap with a Forgeworld Heresy Helmet (Blood Angels I think) and two plastic shoulder pads.
Next is Veteran-Brother Drakin lately of the Red Hunters prior to elevation to the Deathwatch.
Again simple head swap with a Vanguard Veteran head and shoulder pads, the Shapeways Red Hunters pad is very nice and fits well.
Finally is his Infernus Heavy Bolter (hes going to be the only Primaris in the squad so thought it would be nice to use it as a counts as). Whilst not quite finished is a normal Cawl Bolter with the barrel repositioned and the nozzle and tank from a Forgeworld hand flamer.