These things are basically useless. A comp works because the front aperture is just barely bigger than the bullet and the gas column is diverted to the ports. In these the front opening is large enough to pass the barrel (unless they are really long in which case if the aperture is small, they shave and deflect bullets) at that size there is NO restriction of the gas and no effect. The comps mounted as part of the barrel DO work, the aperture is small, reamed to align perfectly with the bore, and gases are diverted. The physics can't be denied, these are purely decorative and non-functional.
Dr Jim