Common Errors For Low R Value in Bradford Assay
You could be measuring outside the dynamic range of the assay (you can only add so much / so little BSA to a certain amount of reagent). 
You could be outside the linear range of your spectrophotometer, usually under 1 is fine, although some old/crappy ones might not even be reliable over 0.5. 
If you're fast you're measuring your different concentrations also at different times. Bradford is a little bit time-dependent, so waiting the recommended time before measuring your standards is not a bad idea. 


Probably it's still pipetting though, try pipetting at least 20 uL in every dilution step and see if you're still off.