Does anyone know the % chance of an instakill with Mehrune's Razor?

says 1% on wiki, but I tested it against Riften guards and it 1-hit them randomly, but often. I think i killed maybe 10 guards, and about 7 were 1-hit kills.

Really? I've used it for the last 20 hours or so and had no instant kills. None.

It is in fact 1%.. I've only had a handful of instant kills, and It's been my primary weapon for 20 levels now.