Found a BUG that explain why the impact force is so strong for the rail gun.
I test this by spawning two ship, a test wall and a rail gun ship, and issuing the rail gun to autofire. When two ship were at the same team, no shield damage were taken by the wall, only the impact force were applied. The wall was pushed back a little, but was able to stand ground forever (fig.1).
But once I set the wall to different team, the wall started to take shield damage, and somehow the impact force were doubled and the wall can't no longer stand ground (fig.2).
I have tested this with target without shield too, and the impact force were applied normally. Only if the target was shielded, does the impact force doubled. I believe this is cause by the rail gun' bullet that go through shield and than hit other part (or shield) on the ship, causing the impact force to be calculated twice. I don't think it was intended, so it must be a bug.
Figure 1. Same team, no shield damage, less impact.
Figure 2. Different team, taking shield damage, more impact.
And these were the ships I used for the test:
