Would anyone be so kind as to approximate the stats for a Shokk Attack Gun and transfer them to 40k rpg? If my understanding of them is correct, then it would be something like a heavy bolter with rolls on perils of the waaagh incurred for doubles.

There's one in OW: Enemies of the Imperium, p. 51, in the description of the Mekboy.

EDIT: Mind you, add a d10 for damage, and your version probably works just as well.

It is also on page 70 of the Koronus Bestiary.

Expanding on this it would depend on who is going to use the gun.

If it was just going to be used by adversaries then the stats as written are probably fine. If it was going to be used by players then I'd be tempted to expand on them considerably.

After all the Shokk Attack Gun isn't just a gun. It's a vacuum tube that sucks things into portals in the warp. It seems like a player is going to try sucking up something other than snotlings at some point.

Things specifically being Snotlings, so I wouldn't allow anyone but an Orkish adventurer to use this.

Indeed but if an Orkish adventurer does get his hands on one how long do you think he is going to wait before he considers sucking up something other than snotlings?

We already know from the 40K mishap table for the Shokk Attack Gun that an Ork can accidentally send himself through the Shokk Attack Gun so unless the player is a cautious Ork (An oxymoron if ever I heard one) there will probably be some experimentation.

I mean who doesn't want to find out what happens when an Ork shooting a Shokk Attack Gun is attacked in close combat and he tries to suck his attacker into the gun?