I can't say for sure, because I don't have this installed, but it sounds as though you're missing the guns. Go to the folder of one of the aircraft in question, and open the xdp file with notepad. Look for the lines which say
<GunStations>
<GunStation UpLimit="0" DownLimit="0" LeftLimit="0" RightLimit="0" RateLimit="0" SystemID="machine_guns" Tracer="40" Trainable="0" Trigger="1"
Type="303calBrowning_gun" Name="Machine Guns" ConvergeDistance="300" Pitch=".1489" MaxAmmo="2000"/>
<GunStation UpLimit="0" DownLimit="0" LeftLimit="0" RightLimit="0" RateLimit="0" SystemID="cannon" Tracer="40" Trainable="0" Trigger="0"
Type="20mmMkIIHispano_gun" Name="Cannon" ConvergeDistance="300" Pitch=".1489" MaxAmmo="600"/>
</GunStations>
I've highlighted the important bit in red. Now go to your Guns folder, and see if you can find an xml file with the same name as the gun in question. If you can't, that's it.
The solution is probably to go to the AvHistory website -
http://avhistory.org/communityserver/files/
and download their weapons pack It is required by the vast majority of quality third party addons.
Let us know if it works!