There was a bug a few months ago, when modding Imperial Hammers with High Capacity Magazine — It would give the railguns 1-2 extra rounds depending on your RNG roll in each "clip", but those extra rounds would be fired off out of sync and without player input.
With a 5-round clip, it would go something like this;
• Hold trigger = 5 shot burst. Release trigger
• Reloading
• 1 shot burst would go off without player input
• Reloading
It got significantly worse when you had a 4-round clip, as it would first fire 4 shots. Reload. Then proceed to fire 2 shots without input.
I immediately removed the mod after nearly hitting clean ships due to the extra shots going off by themselves. Haven't touched the mod ever since that.
I see - only modded 2 so far and both got clip size six in the first run, so either they fixed it by making it default to six or I was very lucky.