Weapons in APB have vastly different speeds at which the player can strafe while aiming down sights.
Mostly this is related to the type of weapon, for example the Obeya only lets the user move at up to 1,39m/s while using marksmanship mode, while an ATAC with a mobility sling can achieve over 3m/s. Commonly, the rule is that heavy and/or long range weapons restrict movement speed, and light weapons such as carbines or submachine guns provide more mobility.
However, there are some guns which are described in-game as being high-mobility yet have paradoxically low movement speeds while using marksmanship mode. Many of these are considered underpowered to a varying degree. The VBR was made significantly more usable when its movenemt speed was improved from 139m/s to a crazy 350m/s.
Here's a list of these guns, their current marksmanship speed and the value I would change it to:
COBR-A: 139 cm/s -> 275 cm/s
ISSR-A (Artemis etc.): 139 cm/s -> 225 cm/s
N-HVR Scout: 139 cm/s -> 175 cm/s
Joker Carbine: 139 cm/s -> 275 cm/s
STAR 556: 175 cm/s -> 275 cm/s
While the STAR's 175 cm/s are appropriate for an assault rifle and equal with the N-Tec, the N-Tec is widely considered superior in the hands of experienced players. With a change like this, the STAR could become a more mobile, CQC-focused alternative with its own set of advantages and disadvantages.
Also, perhaps due to a bug or oversight, the STAR LCR, a heavier long range version of the STAR, has a 275 cm/s movement speed which is much higher than the regular STAR. Of course the last thing the LCR needs right now is a nerf, but it casts doubt onto how each gun's individual speed was decided.