You wrap electrical tape around the barrel near the end of the stock (just in one spot). Use whatever is needed to align the barrel and gives you the free float at the same time.I just ordered some aluminum bar stock to make a couple of dummy barrels to use for this purpose. It's a bit of a pia to bed with the full weight of the barrel installed but you do need something for alignment. I don't think they will need to be any longer than about 16 inches.