ðɪ ˈɛm twˈɛnti ɹᵻlˈaɪd ˌɔn ɐ pˈɜːfɚɹˌeɪɾᵻd ɑːɹtˈɪlɚɹi ʃˈɛl kˈeɪsɪŋ, kəmbˈaɪnd wɪð ɐ ɹˈɪɹ vˈɛntᵻd bɹˈiːtʃ jˈuːzɪŋ pɹəpˈɛlənt ɡˈæsᵻz fɹʌmðə fˈaɪɚɹɪŋ əvə ʃˈɛl, tə ɡɹˈeɪtli ɹᵻdˈuːs ðə ɹᵻkˈɔɪl ʌvðə wˈɛpən.
The M20 relied on a perforated artillery shell casing, combined with a rear vented breech using propellant gases from the firing of a shell, to greatly reduce the recoil of the weapon.