020 - 40k into 30k?

With all the excitement about Betrayal At Calth I'm expecting that there will be an explosion of interest and participation in Horus Heresy gaming. Now this has got me thinking. Can I use my 40k force in a 30k game? There are two ways to do this. The first is simply using a straight up 40k force. 30k forces and 40k forces use the same game system so are technically compatible. However it has been recommended by the Forge World team that you should use the Horus Heresy Force Organisation Chart with any 40k force that is being used against a 30k force. Quite a easy solution which works out well for Xenos armies.
However this might not be for some people because 30k and 40k are slightly differently balanced which is not a problem but in my mind it's not utilising the setting as well as it should.
So my second solution is to use a 40k models with a 30k army list. To keep things simple I'm sticking with marines.
You can take a Space Marine army and use the Legion Crusade Army List. Alot of the fancier toys like Centurions and Razorbacks aren't in the list so it will cut down on units you have available. A problem is the fact that Tactical Squads can only take bolters but if you take the rite of war "Pride Of The Legion" you can have Veteran Tactical Squads as troops which luckily have the similar loadouts to the current Tactical Squads. Pretty easy and quite nice if they are already painting in a first founding colour scheme already.
But I have an Iron Warriors army which I wanted to shoehorn in. The Chaos Space Marine list has some similar entries to the Legion Crusade Army List such as 20 man squads. Again the fruitier units are not in the list so the Heldrakes stay at home but I felt I had enough models to get a half decent force together.
So here is my painted 40k Iron Warriors army in all it's glory:

The collection is as follows:
Chaos Lord in Power Armour
Chaos Sorcerer in Terminator Armour
8 Chosen
3 Helbrutes
10 Cultists
10 Cultists
20 Chaos Space Marines
10 Chaos Space Marines
10 Havocs
10 Havocs
1 Rhino
1 Heldrake

So what can I use? Technically the two HQs can be used. I'd rather not use them as they are very Chaos looking but I'll se what options I have at the end before I discount them. The Chosen can used in one form or another. Two of the Helbrutes have compatible load outs so they are potentially in. The majority of the Chaos Space Marine squads can be used apart from the special weapons.This is a problem I have with the Havocs because all heavy and special weapons in the support quads have to be the same so they are out but I can use the non heavy weapon troopers as basic marines. The cultists are out unfortunately as is the Heldrake but the Rhino is in!
So here is the list I have come up with:
Centurion with a power sword and plasma pistol
5 Vets with a power fist for the sergeant and a meltagun
Rhino
5 Terminators with lightning claws
13 Tactical marines with a powerfist for the sergeant
10 Tactical Marines
Dreadnought with an autocannon and a powerfist

The list doesn't have a massive amount of heavy support. I could have scraped together a few support squads if I had spammed a few more heavy and special weapons in my Iron Warriors. There is also a lack of heavy transports especially in the form of something for the Terminators as  they cannot deep strike. However there is alot of boots on the ground and a couple of powerfists floating about. this would work well with an allied detachment with some heavy hitting stuff. This army could work quite fairly against the Betrayl At Calth army as they end up with rouglhy similar points totals. Swapping the Rhino out for a couple of Chaos Space Marines would make this army compatible for a Zone Mortalis force.
So there you go. A fully painted WYSIWYG Iron Warriors army. Maybe not completely Heresy looking but legal all the same. Bear in mind this is a solution to getting models to play and to get the full experience nothing beats an army of authentic Horus Heresy models. This is mainly an academic exercise in how to get a force to play with but hopefully this will give you a little inspiration to start playing Horus Heresy games. Until next time!