Is 50 minutes of transit time ample in Amsterdam airport?

To add to the other answers.

First, you've booked the entire ticket in one go (I assume that's what you mean as 'one leg') therefore KLM/Delta (SkyTeam) have decided it's possible. And if you miss the connection you'll get the next available seat on that flight (note, that that may very well be the next day and 'next available seat' doesn't guarantee 'next flight to Detroit').

You are just on KLM's recommended transfer time for intercontinental flights (from here)

The standard transfer time at Amsterdam Airport Schiphol to a flight within Europe is 40 minutes and 50 minutes for an intercontinental flight.

If you are travelling to/from Schengen and non-Schengen countries, you should count on having to go through additional security checks and customs inspections. These can substantially extend the time it takes to complete your transfer procedure.

If you do not make your next flight because of a lack of time, you will automatically be booked on another flight. Your baggage will be relabelled and you will not have to retrieve it or check in for the new flight. Your new flight details can be retrieved and you can print out your new boarding pass on a self-service machine.

I've done that sort of transfer in Schiphol before (and have another one coming up) and it's OK, but it's a little rushed. The gates are on 'spokes' (see map here) and the worst case is coming on some high numbered E gate and transferring to some high numbered D gate. But that's still only 30 mins at a brisk walk (and there is motorized buggies that you may be able to use as well).

Also, you don't have to go through immigration to enter the EU side of the airport so you'll probably be OK. Note that you probably will have to go through security at the gate for your departing flight.

If your flight arrives early then you'll be fine, however consider sitting near the front. If the flight is late consider telling the cabin staff and asking them to let you out just after the business class passengers to give you the best chance.

If the flights are booked on one ticket then the waiting flight will also know that you're coming (and you may not be the only one) and will probably wait for you if they know you're in the airport (this varies depending on airline / pilot and number of connecting passengers).

From my personal opinion, this plan sounds to risky, and not recommended. What if the flight encountered some delay on landing? What if there is a delay when you try to retrieve your baggage? even 10 mins of delay might cause you some issue.

Even if everything goes as per plan, I still suggest you to run as soon as the plane lands since it's better to wait in the gate than miss the flight.

On the positive side, Amsterdam Schipol is considered best Airports of 2013 so you can expect everything is more organised than other airport.

You will need to go through security at Schiphol, but since you are in transit between a non-Schengen location and another non-Schengen location, you will not go through immigration. KLM lists the “standard transfer time” as 50 minutes, and they probably allow a safety margin, so with over 1½ hour, you'll be fine, provided that your incoming flight isn't delayed too much. Tripadvisor has an article on the topic, recommending 1¼h to be safe.

Most people don't need a transit visa to transfer between airplanes in Schiphol, but there are exceptions (which don't include India, but do include Pakistan, Nepal and Sri Lanka).