Thanks, I appreciate the information.
I was actually on the TI website looking at the Tac-16 and they state that "The shorter barrels pose a few problems for suppressors. First, the shorter barrels, depending on the bullet weight, have a much harder time trying to stabilize the bullet, ofter resulting in tumbling and off axis wobble. In a suppressor, either one will result in baffle and or endcap strikes. We've done some informal testing with a 10" barrel and wound up with some endcap hits. Any manufacturer's suppressor would have the same problem due to the inability of the barrel to stabilize the bullet. "
However, common sense tells me that if you are shooting rounds that don't keyhole without a suppressor, there is no reason to think that they will all of a sudden start to tumble with one on, especially within the first 6 inches of flight. Sounds like they are just trying to cover their behinds.