Whereas simple blowback is limited to guns using low-power rounds, it is so efficient in this context that in small-calibre semi-automatic pistols it is by now almost ubiquitous. Heavier calibre semiautomatic handguns typically employ a short recoil system, of which by far the most common type are Browning-derived designs which rely on a locking barrel and slide assembly instead of blowback. But blowback guns can be used to fire powerful cartridges if they are of the other two types already mentioned: API or delayed blowback.