I bought up a bunch of them many years ago that were made from barrel cut offs. Then I bought more about a dozen years ago that were made from brass. I bought both the TC style and the transfer plunger (TP) style, not only in centerfire to rimfire but also centerfire to centerfire chamberings. What I found was that how good they shot was entirely a per individual firearm thing. IOW, a very few firearms shot very well with them, some just passable, but most did not. The adapters made from steel did better than those from brass on average FWIW.
I also have adapters to shoot 22 caliber pellets in 22 Hornet and 22-250 centerfire firearms propelled by just a primer. Like the above fun to play with for a while and good enough for backyard pests, but not really a serious conversion.