BUFFS! To H&K railguns

So I had the "luck" of finding one of these things and its matching ammo in my latest playthrough. Well the gun is disappointing, really; weak, bulky, fires an extremely rare and uncraftable ammo and requires an Ups, and to add salt to the injury its not even silent as the description implies.

So I decided to turn it into a suppressed high tech sniper rifle, upped the damage to 50 (the same as .30-06 ammo) and made it as silent and added a unique sound effect while at it(which may not be the most adequate, it is supposed to imitate a charging sound and the crack of a bullet breaking the sound barrier if you want to propose one).
I like your onomatopoeia here.