Likelihood　ratio　(LR)　plays　an　important　role　in　estimating　the　weight　of　evidence　in　firearm　evidence　identifications.　LR　is　computed　from　a　statistical　model　including　the　distribution　of　the　known-matching　(KM　or　within)　and　known-nonmatching　(KNM　or　between)　comparison　scores.　Current　LR　procedures　rely　on　KM/KNM　scores　from　existing　reference　firearm　toolmark　data　sets　or　alternatively　from　generating　a　set　of　test　fires　using　multiple　firearms.　Both　procedures　may　contain　theoretical　or　practical　issues　which　may　hinder　the　LR　procedures　from　reporting　an　unbiased　LR　estimation　in　casework.　In　this　paper,　a　reference　data　set　was　established　from　a　set　of　firearms,　each　test-fired　two　cartridge　cases,　resulting　in　a　basic　data　set　and　a　control　data　set.　The　congruent　matching　cells　(CMC)　method　was　used　to　generate　CMC　scores　that　are　used　to　fit　in　the　KM/KNM　statistical　distributions　for　LR　estimation.　In　the　initial　test,　130　firearms　from　eight　manufacturers　were　used　for　generating　a　reference　data　set　consisting　of　260　cartridge　cases　representing　130　KM　and　8378　KNM　pairwise　breech　face　images.　Test　results　showed　that　the　KM　and　KNM　distribution　intersect　at　CMC　=　2,　which　is　equivalent　to　LR　=　1　(equally　to　support　both　the　prosecutor　and　the　defense　propositions).　When　the　CMC　threshold　is　increased　to　6　or　more,　the　LR　values　are　higher　than　a　million,　which　can　provide　extremely　strong　support　to　the　conclusion　of　the　same　firearm　(or　the　prosecutor＇s　proposition)　in　the　casework　of　firearm　evidence　identification.