What level do you need to be before experimental weapons drop I got my first one today I am level 28
My friend is 26 he hasn’t found one…also anybody know the drop chances? . Only been playing a few week still learning.
Noob 
thanks for any help guys
You need to be level 25. Chances are random. Good luck on the hunt. 
Level four rivals are your best chance 
You need to be level 25. (Supposedly the Rivals on Himfjall can drop them at low levels, but I’ve never verified.)
As for the drop chance? No one knows. Each enemy type, class, and Rival level, have their own drop tables. Any Rival can drop the Experimentals. Even Hunters and Prototypes can drop them. But, the odds are vary wildly.
Thanks for the help guys
Yes, yes, and yes.
Level 25 required
Random chance
Higher level Rival = better chance
Also, in multiplayer, items are random for players, from the same rival.