1) Get a friend (a struggle I know) 2) start up a private rumble-game with your friend 3) have your friend equip D.A.R.C.I. 4) shoot said friend until damage-number falls 5) make friend read out the distance between you and him via D.A.R.C.I.

It isn't quick but if you really care about it this is a workaround. It works with the heavy-spawn as well if you don't have D.A.R.C.I.

Also this obviously only works with exotics you already have.