[quote=Raineh Daze]
Remind me what about psychic space elves and emotion-fuelled gods is scientific.
[/quote]

Not that part specifically (though it does prove my point that magic isn't the same as science). But a lot of the Imperium's and especially the IG's equipment is laser guns, space ships, and genetic enhancements.
You can actually get relatively detailed specifications for how a Bolter works; it's got a similar principal to Gyrojet.