Digital BW, The Print

I have printed the calibration target with 1ink levels 100, and when 
I look at the print, ink 1 black maxes out at about 45. Is this 
common. I read that it is normally around 80-85?

Windows XP, Epson 4000, QTR 2.2, UC, Matte Black, HPhotoRag

I plotted the luminance with Eyeone spectrophotometer. From step 45-
100 I get luminance readings of 18-19

Visually most other inks seem to max out at about this point as well

Any ideas or is this normal and should I proceed with curve 
creations based on this?

Cheers and thanks

Richard