ðɪ ˈɑːɹmi hæd pɹˈiːviəsli bˌɪn jˈuːzɪŋ ðə .θˈɜːɾi ˈeɪt lˈɔŋ kˈoʊlt, ænd ðə kˈɑːɹtɹɪdʒᵻz ɹˈɛlətˌɪvli pˈʊɹ bɐlˈɪstɪks wɜː hˈaɪlaɪɾᵻd dˈʊɹɹɪŋ ðə fˈɪlᵻpˌiːn ɐmˈɛɹɪkən wˈɔːɹ ʌv wˈʌn θˈaʊzənd ˈeɪthˈʌndɹɪd nˈaɪnti nˈaɪn nˈaɪntiːnhˈʌndɹɪd tˈuː, wˌɛn ɹᵻpˈoːɹts fɹʌm jˈuː.ˈɛs. ˈɑːɹmi ˈɑːfɪsɚz wɜː ɹᵻsˈiːvd ɹᵻɡˈɑːɹdɪŋ ðə .θˈɜːɾi ˈeɪt bˈʊlɪts ɪnɐbˈɪləɾi tə stˈɑːp tʃˈɑːɹdʒᵻz ʌv fɹˈɛnzid mˈɔːɹoʊ dʒjˌʊɹɹəməntˈɑːdoʊz ɪnðə mˈɔːɹoʊ ɹᵻbˈɛliən, ˈiːvən æɾ ɛkstɹˈiːmli klˈoʊs ɹˈeɪndʒᵻz.
The Army had previously been using the .38 Long Colt, and the cartridge's relatively poor ballistics were highlighted during the Philippine–American War of 1899–1902, when reports from U.S. Army officers were received regarding the .38 bullet's inability to stop charges of frenzied Moro juramentados in the Moro Rebellion, even at extremely close ranges.