It wasnt big missile, if you had seen my comparison of shaheen II with Agni II.
Shaheen II is smaller in length(20%less),slightly bigger in diameter(10%more) but weighted 6.6 tons more.
Volume of cylinder = π r ^2 h is almost same for Agni II and Shaheen II but
Shaheen II used no composite in second stage(Agni II did have it). There is also less efficient solid rocket motor and old jet vanes technology which burns fuel more than agni II
Shaheen III pic from this year test showed 1.4 meter diameter but I couldnt conclude find any considerable change in height. Once Details about payload, weight are revealed then it will be easy to approximate range of Shaheen III.
@MaarKhoor
You either need 3 stage rocket to cross 4000 KM or 2 stage rocket with 2+meter diameter as agni III+ all composite frame.