To remove the beginning delay delete the first (.750) seconds delay.
Also, if you're in a shotgun 1v1 you really shouldn't be aiming down sights. You wanna make yourself as much as a moving target as possible, the only time you should be ADSing is if you know you can hit a headshot on your opponent or when you're peaking them for the first time. Other than that ADsing simply just slows you down.