Taking into account the fact that with the old heavyclip all the buckshots hit the same spot and still deliver full damage, I am 100% positive that you get the full force with them too. Not to mention that due to really bad game design heavyclip no longer has 100% jitter reduction so that question doesn't apply to heavyclip anymore.
As to the question of if you get more force, when you think about it, if for the example the target was a flat surface - without heavyclip all your buckshots have a spread that is random around the point of 0 jitter, buckshots hitting above,below, left and right to that point. so you will get different sizes of forces that push the ship, with some greater than others. However, because the jitter is completely random, over time you will see that on average they all approach 0 jitter, meaning that it technically has the same push - only less consistent.
So if you want your push force to be more consistent between shots and not only in average, use heavyclip.
It's like taking a chance each shot for a high or low push force, or having a guaranteed medium push force each shot.