@riccetts, Did you ever get this to work properly?
I decided to tinker around some more today and came up with a far better solution one that allows you to move the barrels and use RPG's/Grenades if you wish!!!
There are 2 ways to set this up a lazy way and the proper way. First of all use a door segment and place the door such as in my previous posts screen shots. Set the doors strength to what you wish besides 0 (higher values can allow you to use multiple explosives on the door).
Exp-loadable (yes/no) it doesn't matter just be sure to adjust the explode damage to 0 if you decide to. Now use the script in the doors "main" field.
:state=0:state=1,nobulletcol
That's it lazy way done!! 
However this way you will not get bullet holes on the door and actually bullets will travel through so you may see holes on the other side.
Now the proper way! After these steps place this script in the "destroy field"
:state=0:state=1
:state=1:activateifused=1
:state=1,alphafadeequal=100:decalphafade=0
:state=1,alphafadeequal=0:state=2,destroy
and place a name in the "if used property" ex: "door2"
Next, place a new door from the entity model, not the segment. Do not change anything (strength must be 0) besides the "main" script and the name of the entity, use the previously created name (door2). Use this for the "main",
:state=0,activated=1:state=1
:state=1:destroy
Lastly align your door right in front of the segment door.

You now have a door that can only be destroyed through explosions! The door will leave bullet holes/sparks/chips when shot (depending on type of door).
If you liked this run-around let me know so I will continue to devote my time for users on the forums!

As always, Game on! -2S!K Productions