To add voxels to the game, make a new mix named expand##.mix, where ## is any 2-digit number. This is mainly for voxels, some other files go in ecache##.mix. Check Guide: File Types (under RA2) on this site for info on what file type goes where.

For units (not buildings) you do not specify turrets, the file name does. For example, m113tur.vxl is automatically the turret of m113.vxl . Simply tur is added to the filename. For barrel, i think you add brl , but im not sure, double check that.

meselfs himself!