I found the plans here:
https://plans.rocketshoppe.com/estes/est1980/est1980.pdf
The length of the tubes is not given, but the overall rocket length is 40.75" (according to the face card). The tubes in the parts display are shown the same length; I'd guess they are 18". That would make 36", so to get that total length, a 4.75" long nose cone (sans shoulder) would be needed. Given that the tube is BT-50 (based on the stated diameter) and the cone appears to be a long ogive, that seems reasonable.
Just a guess, of course; but add to that the fact that the manufacturer, Estes, has no particular reason to build a rocket with odd-length tubes, and 18" is a standard length, and I think that cinches my case.
