ðə wˈaɪdli ɐdˈɑːptᵻd səlˈuːʃən, ɪnvˈɛntᵻd ɪn wˈʌn θˈaʊzənd ˈeɪthˈʌndɹɪd sˈɪksti θɹˈiː baɪ wˈɪljəm pˈælaɪzɚ, kənsˈɪstᵻd ʌv ɛnlˈɑːɹdʒɪŋ ðə bˈoːɹ tʊ ɐksˈɛpt ɐ ɹˈɔːt ˈaɪɚn tˈuːb kˈɔːld ðɪ ɐ tˈuːb ˌɪntʊ wˌɪtʃ ðə ɹˈaɪflɪŋ hɐdbɪn kˈʌt.
The widely adopted solution, invented in 1863 by William Palliser, consisted of enlarging the bore to accept a wrought iron tube (called the A tube) into which the rifling had been cut.