Several things:
Better ranged damage (x2) raise P90 damage by 25%, this is what you miss, and can't really fit in, that's why people pick up big guns and use LSW for speaking, because the weapon is broken (2x BRD is only 13% increase for it) while doing ~50% better damage before armor and BRD, and even with those in mind it's still considerable advantage, meaning you have to burst one more time to really abuse p90.
The problem is, that you can't do that, because you will NOT survive burst with 205 hp on jet. Without jet (but with beer and psycho) it is possible, but you will not be able to burst three times to do enough damage.
I don't really think there's way to do sneak build being able to reliably take down big gunners, with exception to rocket launcher build.
And honestly other builds are now very much broken doing way too low damage per shot, increased to insane amounts on critical hits. Meaning you will not likely survive better with 2 lifegivers. You're really just going to pop up and burst if possible, and for that you have to max your sneak, even with ghost thing.
I really wonder if or how Ghost really work though.
Wrong way of thinking.
Bonus ranged damage is effective on all guns if you shoot them point blank , but minigun benefits from it the most and BRD becomes useful even on ranged bursts not only point blank that's why people don't take BRD for all weapons except minigun. Not having brd for p90 is not really a issue but in the same time it is , it's complicated.
Since this is a sneaker p90 is the wrong weapon choice , can't abuse any range advantage , p90 is good only point blank , sneaker is not a tank and can't take much damage , so it can't take advantage of point blank bursts all the time it means you are gonna be very limited at what you can do. In other words p90 is not flexible on a sneaker , it's good on a proper 2xtoughness sg burster build that can tank shitloads of damage but not on a sneaker , since you use CLJ.
I'm tired of telling people self sufficient combat characters are inefficient and can't compete with proper power builds combat wise , i just can't make a bad build , just make a damn multi purpose crafter and use this is you really want a p90 sneaker burster build but it's still shit.
Take silent running level 6 , then ghost , lifegiver , weapon handling , Brof uses Jet , nuka , cigs. High perception is needed to see other sneakers , it's essential for every sneaker no matter what the build , since sneakers are mostly used as scouts not actual fighters , it's another reason for high perception and it gives you a lot of sight that allows you to see the enemy from afar and have awareness of their current position that way granting you an edge to plan your attack. Oh yeah and it helps you to keep distance on potential targets.
btw there are other versions of the build like to drop some agility and perception , put in str and use buffout to balance the jet penalty since you really don't need so many action point's for p90 and that way gaining more carry weight , use lifegiver instead weapon handling - more health , but then again loosing perception(sight + hit to chance on distances) on a sneaker is painful yet it is a choice.
Well it can take a lot of abuse for a sneaker but still not enough to act as a tank since combat leather jacket doesn't do wonders. Then again there is another choice for this build , you can drop 2 endurance and put in perception if you really want the high perception or extra action point if you max out agility but that's kinda pointless. Or put 2 point into strenght and make it an universal sneak sg burster build , but that is inefficient ofcourse.
I just can't stand reading false information that is provided for new players.
