If it’s hard to see on your phone, watch the whole video. I show the scenes again zoomed in.
You can fire for 350 milleseconds before the crosshair gets wider. So if you shoot it in burst you can strech ranges by a lot (and save a lot of ammo), but it gets impractical at later rounds.
We've seen similar mechanics on some other guns (PaP 4 Nova, one of the SMGs) but I never noticed it on an Akimbo gun.
The reset, the time you need to wait between bursts seems to be 180ms. The video was taken with Double Tap – Double Time and no Rapid fire.