My personal opinion having traveled by this train is that it can be made into a 22 Coacher as told by you if a Pantry or at least Buffet Car along with an H1 (1st + 2nd AC) coach is added. If Akal Takht Exp can have an H1 and Kumbh Exp can have a Pantry then Durgiana Exp needs both these kinds of coaches.
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PS: I remember that this train started with 3 AC coaches (1 second and 2 third AC coaches). Within a few years, the 3rd AC coaches increased...
more... from 2 to 3 and then 3 to 4 but the 2nd AC coach is only one. Today, it has 5 AC coaches but an extra 2nd AC coach can also be added for middle tier family passengers like me. I have seen my 2nd AC coach and it was packed with passengers right from Calcutta to Amritsar (although some alighted but the seats were replaced by new people). This train also needs to be de-linked from rake sharing with KOAA-AGC SF Exp and upgraded with an LHB one. Increasing it's frequency to 3 or 4 days in a week can make these reforms possible. By March, 2016 with the
#EDFC stretch between Sasaram and Durgauti opening, this train may also be speeded up on the Grand Chord Route. Let's hope that IR has grand 120 Kmph MPS plans for it :-D