I was going to buy one once because they were cheap. Then I went to Bullberry's websight and read where Fred had started with a long barrel and cut it off an inch at a time. When he got to around 16" the muzzle blast was moving stuff on the walls and he could not even get a Crony reading with every shot because of the muzzle blast.
I change my mind and did not buy one. Always wondered if the blast was really that bad. I just decided that my 223 shot plenty good.