I think I found a slight glitch. I have tested this issue in an empty world with and without your mod (no other mods present).

A heavy armor block is supposed to take 6 hits from a 122mm gun. Upon placement of a heavy armor block (3x3x3) and six rounds fired a single heavy armor block is destroyed. However, if the 122mm turret is placed and the world is saved and reopened, a single layer of heavy armor blocks (3x3) are destroyed by a single 122mm round.

I tested this again with the vanilla gatling turret. At a range of 200m and a heavy armor block - the gatling turret removes approximately 15-20% of the blocks health in a single reload. However, the same gatling turret under the same conditions above (save world and reopen) destroys the heavy armor block before needing to reload.

It appears that the damage is being multiplied by a factor of 6 after the world is reopened. Additionally, turrets placed during the current session are using the correct damage figures (6x hits to destroy 1x heavy armor block). However, any turret placed in a previous session is dealing 6x damage. Two 122mm guns placed on the same grid (one in a previous session and one during the current session) are dealing different amounts of damage (1 hit 3x3 heavy armor destroyed & 6 hits 1x heavy armor block destroyed).

Any thoughts?