After I ran some calculations it doesn't seem like any change to the way heavy clip jitter reduction works will do the trick. I mean, it might do the trick but it will ruin other weapons that use it.
95% reduced jitter will mean a maximum jitter angle of 0.2 degrees on the heavy carronade when applied heavy - giving you a maximum spread of 1.5m at maximum range. due to the way that aoe secondary damage type works, and decreases linearly after the point of half the radius, at maximum range, with extreme end cases, you will be doing 86.7% of the damage on average at the center point of impact - which is still able to one shot destroy a heavy gun.
In addition to the still quite devastating damage, the carronade's heavy gun kill radius will be be increased from 2m to about 2.6m on average(so it actually makes it better).
(I am intentionally not talking about balloon killing and only the component destroying - more commonly heavy weapon destroying because only the aoe damage of the carronade, the shatter damage will get affected. Due to a spread at maximum range of 1.5m, any balloon will still be fully vulnerable to it, with slight exceptions with the pyramidion's balloon in various angles, that might cause some armor hits.)
Now for this change to be actually effective in the sense of taking away the carronade's extreme ability to snipe guns and or balloons with heavy clip, one will be forced to decrease jitter by 70-80%.
Right now with the proposed 95%, not only that it doesn't do the trick, it is already starting to ruin the hwacha with heavyclip - you will have 6.25m of spread at maximum range, and with only 7m of aoe radius and the way aoe damage behaves, you are starting to lose quite a bit of damage. Decreasing the spread even more is simply not an option because it will ruin everything that uses heavyclip. Concentrate on the carronade, it is the problem, not the ammo type.
Also, heavyclip exceptions for carronade are quite a dumb solution in my opinion. If you have to make exception for certain weapons you already know something is stupid in the weapon itself, and you're just trying to find a way around it. If you do it, might as well do it right and change the weapon itself.