measures approx. .31cal; First one we've ever handled and it's awesome! What a great look these have! 31.5" heavy Oct. barrel; Original Syst-Aydt Falling Block system operates smoothing; rear peep sight; very pronounced comb on shoulder stock with large brass crescent butt plate; wood has some normal marks & wear but for it's age is very nice; dual trigger set; made in Germany; no SN# that I can see; no FFL transfer required