I tried a couple on my rimfire benchrest rifle and they seemed to work, but not as well as a weighted tuner near the muzzle.
There was a test that compared extremely large-diameter rimfire benchrest barrels, vs smaller-diameter barrels with tuners and the ones with tuners that were properly-adjusted shot better. Many people use 10.5 lb rifles with tuners for both that class, and the 13 lb and Unlimited classes...and win!
If I can't be with the rifle I love, I love the rifle I'm with!!