Milan and Bernina Express

I have never taken the Bernina Express, but it is advertised as running from Tirano, Italy, to Chur, Switzerland, and the tours from Milan only go as far as St. Moritz, which is well short of Chur. Now, for all I know the section of the rail line between Tirano and St. Moritz may be more spectacular, but I wouldn't want to try to do the Bernina Express as a day-trip from Milan if it meant missing a large chunk of the ride. Looking at a map, it appears to me that you'd be getting less than half of the Bernina Express on that tour.

There are some other lovely train rides in Switzerland (though mostly without the panoramic cars), and I'm sure there are good options that would be workable from Milan. However, it might need to be an out-and-back trip along the same route.

The train to Tirano is scenic in and of itself. Sit on on the left side to see the lake. There's no need to catch the panoramic train. There's little real visibility difference. Besides the ordinary cars have operable windows which is much better for photos.

The Bernina Express is not ideal as a day trip from Milan due to the times involved. Travel time from Milano to Tirano (where the B.E. departs from) is 2H:32M in each direction. The trip from Tirano to Chur is 5H:20M, and doesn't arrive in Chur until 18:20 so that's somewhat late to head back to Milan. As I recall, the panoramic trains only have one departure per day in each direction, but there are "regular trains" operating on the same route.

There are a number of variables that might help. For example, if you were to travel only part way on the B.E., the trip would be shorter and more manageable. For example, you could only go as far as St. Moritz or Pontresina, and then return to Milan by regular train. You could use regular train for the trip instead of the panoramic cars, which would provide more flexibility in timing.

I don't know of any tours or guides that offer that trip, but perhaps one of the other forum members will have some information on that. I'm not really sure what benefit a guide would be, as you're just going to be sitting on a train looking at the scenery.

Milan to St.Moritz (5 hours and half) and back is already on the limit of feasibility of what you can do in a single day, and you have to leave very early from Milan if you want to get back by night. Getting to Chur and back in a single day is impossible, and anyway the most interesting section is the one up to St. Moritz. You can easily do the trip on your own, remember to take passports with you.

I am sure some of the transportation experts may find something better but as of now, this is what I can find. From looking at Bahn.de https://www.bahn.de/p_en/view/index.shtml to get an idea of train schedules, trains run runs almost hourly but you do have to change trains, in most cases, just walk across the platform. Travel duration from Tirano to Chur is anywhere from 4:03 to 5:30. Depart Tirano at 9, arrive Chur at 1:03 PM. Depart Chur at 1:58 PM, arrive Tirano 6:19 PM. Then the bus back to Mirano. Roughly 8 hours on a train, spend the night and come back the next day. And then you are going to pay a guide to sit next to you. Most of the scenic mountain trains I have been on did not need any explanation.

It is local trains not the official "Bernina Express." The train might not be fully decked out with observation windows but most of the windows are large enough for great views.

Csu, just remember that in order to depart from Tirano at 9:00am you must leave Milan at 6:20am.

There should be very few direct trains Tirano-Chur, almost all of them require a change in Pontresina or St. Moritz as the Bernina line has a different electrical system than the main Rhatische Bahn network. An engine change in Pontresina is possible but cumbersome, this is why a change is required in most cases.

I thought the BE only runs on those selected days. However, I found out it runs every day.

eils, you appear to be under the major misapprehension that this is a special train that runs where no other train runs - wrong.
The Bernina line is a normal Swiss Railway line, which means it has at one train per hour, throughout the day, 7 days a week.

almost all tour operators offers this route

It is a train, not a special tour, you do not want a tour operator, you just need to catch the train. The Bernina Express is one particular extra limited stop train that runs on the Bernina line, you see the same mountains whichever of the hourly trains you take.

But, you also need to look at a map, preferably a rail map. The Bernina route is tangential to Milan. You get a train from Milan to Tirano, and change there to the Bernina line. You then end up at St Moritz, or you can continue to Chur (more mountains). This puts you on the north side of the Alps, the wrong side for Milan. The quickest way back across the Alps is the way you just came.
I.e. you really can't do this on a day trip from Milan. It is best done when you actually want to cross the Alps, which is what the line is designed to do.

The Bernina line actually is designed to link some almost abandoned Swiss valleys on the Tirano side to their motherland: to these areas, the railway is a lifeline. It was never planned as a major Alp crossing route. The Bernina line is very steep and has no major tunnels, this is why it is so scenic and this is why it is so slow.