ðɛɹwˌɜː sˈɛvɹəl ɹˈiːzənz fɔːɹ ðˈɪs: ðə ʃˈɛl kʊd nˌɑːt biː mˌeɪd tə fˈɪt tˈuː klˈoʊsli ˌɪntʊ ðə bˈoːɹ ʌvðə ɡˈʌn, æz ɪt wʊd nˌɑːɾɐv bˌɪn pˈɑːsᵻbəl tə ɹˈæm ɪt hˈoʊm; ðə vəlˈɑːsᵻɾi əvə ʃˈɛl dᵻpˈɛndz, ɐmˌʌŋ ˈʌðɚ fˈæktɚz, ɔnðə lˈɛŋθ ʌvðə ɡˈʌn bˈæɹəl, ænd ðə nˈiːd tə lˈoʊd θɹuː ðə mˈʌzəl nəsˈɛsɪtˌeɪɾᵻd ɐ ʃˈɔːɹt bˈæɹəl sˌoʊ æz tə mˌeɪk ðə mˈʌzəl æksˈɛsəbəl tə ðə lˈoʊdɚz; lˈeɪɾɚ tˈaɪps ʌv ɛksplˈoʊsɪv wɜː suːpˈiəɹɪɚ; ænd mɛɾɐlˈɜːdʒɪkəl tɛknˈiːks ɪmpɹˈuːvd tʊ ɐlˈaʊ ɐ hˈaɪɚɹ ɪnˈɪʃəl pɹˈɛʃɚɹ ɪnðə bɹˈiːtʃ ʌvðə ɡˈʌn.
There were several reasons for this: the shell could not be made to fit too closely into the bore of the gun, as it would not have been possible to ram it home; the velocity of a shell depends, among other factors, on the length of the gun barrel, and the need to load through the muzzle necessitated a short barrel so as to make the muzzle accessible to the loaders; later types of explosive were superior; and metallurgical techniques improved to allow a higher initial pressure in the breech of the gun.