Beam Euler :
f = (F*L*L*L) / 3*E*I

f = displacement ==> 1,6156 mm with :

F = Force ==> 2000 N
L = 1000 mm Beam lenght
E = 210 000 N/mm2 elastic module
I = 1964944 mm4
with D = 100 mm ; s = 6 mm D ( Outsidiameter pipe) s (thickness)

Caesar result ( only Load F ,without Weight case):
f = 1,644 mm

Differenz : 1,76 % << your 14 % !!!!