Perfect beam convergence was impossible to attain in reality.
No energy weapon could produce completely parallel beams where all of the light photons or energy rays shot forward without ever intersecting with or drifting away from each other.
The weapon in question needed to be built according to a level of precision and control that not even the best materializers could attain.
It was easy to design a perfect weapon in a virtual or imaginary environment, but reality was messy due to the influence of many variables that simulation programs could never fully replicate.