The RE45 being changed to a charge energy burst weapon, instead of just keeping the same functionality and being swapped to heavy ammo still boggles my mind.
So many of the energy weapons have that delay before firing that IRL would be a death sentence to any soldiers on a battlefield for a CQC to Mid-range method that none of these would be developed for a serious military.
The charge rifle being the only one with a charge delay makes sense. In the original Titanfall games it was for pilots to use in their anti-Titan slot. It was something you were aiming at the broad side of a moving barn.