Dry Ribs

What was the chamber temp of your smoker?  At first glance they sound undercooked.  

I always buy the larger SLC cuts and at 225F chamber temp they were usually perfect for me right around 6 hours.  I've had them take as long at 7 hours though at the chamber temp before they passed the bend test.  I always smoke mine unwrapped, no spritzing or spraying.  Nice bite, juicy and tender. 

Now my wife who likes her ribs fall-off-the-bone, thought they were dry and tough the way I liked them.  I bumped the chamber temp up to 250F. The longest I've had any of them go is just over 6 hours before they pass the bend test.  At 6 hours they are just on the verge of being overdone for me but my wife now loves them. 

Below is the information about the bend test.  Some folks use the toothpick test too.  I've never found the need to do so.    

http://www.smokingmeatforums.com/t/165426/bend-test  

I agree with nb, the last ribs I made were undercooked and tough but not dry. Maybe try foiling them if you didn't this time. It will hold the moisture in and cut the cooking time.