I made a similar thread a couple of months ago, back in March, about basically the same thing here: https://forums.focus-home.com/topic/36964/strange-ads-animation
I'll link the same video I posted before in this thread, as the animation hasn't changed at all.
I'm mainly talking about this bug again because of Hardcore Checkpoint. You're often down to your good ol' ruski Mosin-Nagant in HC, and this animation can really fuck you over here. Due to the length of the rifle and the lack of any 1x optics (as all 1x optics stay centered regardless of weapon movement), this animation will prevent you from using your sights for what feels like an eternity.
Hitting your shots is paramount because it's a bolt-action rifle, and since it doesn't exactly fire very fast, you'll mainly end up using this gun while peeking in and out of cover. This is another reason why this animation is particularly painful in HC, because if you accidentally ADS before you fully peek out of cover, your weapon will launch upwards, and it takes a solid second or more for your sights to realign. In HC, this can cost you your life as the bots are no joke and will kill you fast, especially in close quarters.
This animation was in Ins2014, but it was considerably faster. Now, many animations in Ins2014 were fast due to the nature of the engine (no way around it), but it helped a lot in CQB. I doubt many people died because of this animation. In Sandstorm, though, it's actually faster to leave ADS and re-enter ADS than it is to wait for this animation to complete, which is ridiculous. I think it just needs to be sped up, even if it looks a little insane, because it makes the gunplay smoother in CQB.