There's old question what "Red Dot Laser Sight" actually is - Red Dot Reflex Sight or Laser Sight . I personally think its reflex sight since it has no maximum range. I would suggest those rules:
Red Dot Reflex Sight - It reduces times required to aim by half (so you can aim to get +10 as Free Action and +20 as Half Action).
It's better because it works with Semi- and Full-automatic fire and it's better when used with accurate weapons, however it's downside is that it can give you maximal bonus of +20, while with current version of RDLS you can get +30 is you spend full action aiming, thus making it less useful when sniping since you usually can easily aim (it also doesn't dive any bonus to inaccurate weapons, but I can't remember any Inaccurate weapons worth using anyway). I would say it's better than current version so I would increase it's cost (I would say 150 Thrones, Rare sounds good, or you can keep it limited to single shot, then it should be 50 Thrones, Scarce)
Laser Sight - Same effect as Red Dot Sight, except it only works if the target is within [you PBx5] meters from you, because if target is further away the dot becomes to small to actually help target (the GM should reduce the range in bad conditions like fog or rain or in red light and increase in dark conditions), however if you use Telescopic Sight (or any similar equipment) is has no maximal range unless there's fog/smoke/etc. which would . It can be mounted under the barrel so gun can have both Laser and another sight (note - it effects doesn't stack with Red Dot Reflex Sight).
Cost - 50 Thrones, Scarce.
Hey, what's tha-TAKE COVER!
I created this rule because while it's kinda complicated without it Laser Sight would be overpowered, especially then combined with Telescopic Sight (of course you forbid to use them together and/or don't allow it used in conjunction with Semi- or Full-auto). GM should use it only when Laser Sight's used by or against players of course.
Whenever you use laser sight target anyone who can see him/her/it and are withing their PerBx5 meters can take take Awareness test as Free action.
It's base difficulty is Very Hard (+30) with following modifiers:
You used half action to get +20 bonus - +10%
Opponent is in combat - +10%
He/she/it can see you - +10%
It's dark - +10%
Target would normally be surprised by your shot - -10% (This doesn't apply if the player/opponent has Paranoia talent. HE IS ALWAYS WATCHING FOR SNIPERS. YOU WON'T SURPRISE HIM.)
You are not the target - +10%
If test successful the one who noticed it is no longer surprised (if they were in the first place) and can shout to alert everyone else, and if he was the target he also gets +10% (plus additional +10% for each 2 degrees of success) bonus to dodge the the shots from the gun noticed Laser Sight is attached until his next turn.
Note non thinking opponents as animals, non-combat servitors, daemons, etc. don't take this check while sapient xenos who don't know what exactly Laser Sight is should take Difficult (-10) Int test to figure what it is in time.
It can be Infra-red (100 Thrones, Scarce, it can also made from regular Laser with Diffcult (-10) Tech-use or Challenging (+0) Armourer skill check), making it visible only to those who have equipmen or natural ability to see infra-red light so it can give bonus only if you have said equipment but it doesn't let targets take Awereness check to notice the dot unless they also can see infrared light.