I tried a de-resonator on both a .30-06 bolt and a .308 single shot, played with them a while and found that if you tinker with the placement on the barrel I could tighten my groups by about 1/4 inch at 100 yards. It was an interesting experiment, but the device was so darned ugly I took it off the rifle. My rifles are hunting rifles and that 1/4 inch simply didn't make enough difference to justify that blob on the barrel.
Still, they're reasonably inexpensive and they did work to a measurable degree. If that little difference matters, then it works.