活(huo)塞(sai)原理，短(duan)(duan)(duan)沖程(cheng)(cheng)(cheng)活(huo)塞(sai)傳(chuan)動(dong)(dong)(dong)(dong)(dong)(dong)。短(duan)(duan)(duan)行(xing)(xing)程(cheng)(cheng)(cheng)活(huo)塞(sai)傳(chuan)動(dong)(dong)(dong)(dong)(dong)(dong)：這是(shi)最常見的(de)(de)(de)(de)(de)(de)(de)(de)(de)氣(qi)(qi)(qi)(qi)動(dong)(dong)(dong)(dong)(dong)(dong)式(shi)系(xi)統。原則(ze)上(shang)活(huo)塞(sai)行(xing)(xing)程(cheng)(cheng)(cheng)不(bu)會大(da)于(yu)(yu)活(huo)塞(sai)本(ben)體(ti)(ti)(ti)的(de)(de)(de)(de)(de)(de)(de)(de)(de)直徑，因(yin)此(ci)在結構上(shang)重(zhong)(zhong)量也(ye)比(bi)較輕。此(ci)外由(you)于(yu)(yu)活(huo)塞(sai)的(de)(de)(de)(de)(de)(de)(de)(de)(de)運(yun)動(dong)(dong)(dong)(dong)(dong)(dong)范圍不(bu)大(da)，因(yin)此(ci)不(bu)會造成(cheng)槍(qiang)枝重(zhong)(zhong)心嚴重(zhong)(zhong)的(de)(de)(de)(de)(de)(de)(de)(de)(de)前(qian)后位移，對于(yu)(yu)射擊時(shi)(shi)的(de)(de)(de)(de)(de)(de)(de)(de)(de)穩定度(du)(du)有很大(da)的(de)(de)(de)(de)(de)(de)(de)(de)(de)幫助。目前(qian)采(cai)用(yong)短(duan)(duan)(duan)行(xing)(xing)程(cheng)(cheng)(cheng)活(huo)塞(sai)設計的(de)(de)(de)(de)(de)(de)(de)(de)(de)槍(qiang)枝例如(ru)(ru)AR18長(chang)行(xing)(xing)程(cheng)(cheng)(cheng)活(huo)塞(sai)傳(chuan)動(dong)(dong)(dong)(dong)(dong)(dong)：顧名思義長(chang)行(xing)(xing)程(cheng)(cheng)(cheng)活(huo)塞(sai)傳(chuan)動(dong)(dong)(dong)(dong)(dong)(dong)式(shi)的(de)(de)(de)(de)(de)(de)(de)(de)(de)行(xing)(xing)程(cheng)(cheng)(cheng)遠大(da)于(yu)(yu)活(huo)塞(sai)直徑，值得注意的(de)(de)(de)(de)(de)(de)(de)(de)(de)是(shi)在這種設計中(zhong)活(huo)塞(sai)與氣(qi)(qi)(qi)(qi)缸(gang)的(de)(de)(de)(de)(de)(de)(de)(de)(de)體(ti)(ti)(ti)積也(ye)代表氣(qi)(qi)(qi)(qi)體(ti)(ti)(ti)的(de)(de)(de)(de)(de)(de)(de)(de)(de)留(liu)滯時(shi)(shi)間(jian)比(bi)短(duan)(duan)(duan)行(xing)(xing)程(cheng)(cheng)(cheng)活(huo)塞(sai)的(de)(de)(de)(de)(de)(de)(de)(de)(de)氣(qi)(qi)(qi)(qi)體(ti)(ti)(ti)留(liu)滯時(shi)(shi)間(jian)長(chang)，因(yin)此(ci)以相對的(de)(de)(de)(de)(de)(de)(de)(de)(de)角度(du)(du)來說氣(qi)(qi)(qi)(qi)體(ti)(ti)(ti)推動(dong)(dong)(dong)(dong)(dong)(dong)活(huo)塞(sai)的(de)(de)(de)(de)(de)(de)(de)(de)(de)導孔(kong)必須要接(jie)近(jin)槍(qiang)口的(de)(de)(de)(de)(de)(de)(de)(de)(de)位置，然后導引氣(qi)(qi)(qi)(qi)體(ti)(ti)(ti)回傳(chuan)給活(huo)塞(sai)再向后透過連(lian)動(dong)(dong)(dong)(dong)(dong)(dong)的(de)(de)(de)(de)(de)(de)(de)(de)(de)結構推動(dong)(dong)(dong)(dong)(dong)(dong)槍(qiang)機(ji)。這個必須靠(kao)近(jin)槍(qiang)口的(de)(de)(de)(de)(de)(de)(de)(de)(de)設計原因(yin)是(shi)因(yin)為如(ru)(ru)果氣(qi)(qi)(qi)(qi)導孔(kong)往槍(qiang)機(ji)的(de)(de)(de)(de)(de)(de)(de)(de)(de)方向靠(kao)近(jin)會提前(qian)排出推動(dong)(dong)(dong)(dong)(dong)(dong)彈頭的(de)(de)(de)(de)(de)(de)(de)(de)(de)氣(qi)(qi)(qi)(qi)體(ti)(ti)(ti)以致于(yu)(yu)降(jiang)低彈頭的(de)(de)(de)(de)(de)(de)(de)(de)(de)威力(li)。相對地來說長(chang)行(xing)(xing)程(cheng)(cheng)(cheng)活(huo)塞(sai)結構的(de)(de)(de)(de)(de)(de)(de)(de)(de)重(zhong)(zhong)量也(ye)比(bi)短(duan)(duan)(duan)行(xing)(xing)程(cheng)(cheng)(cheng)活(huo)塞(sai)結構較重(zhong)(zhong)，不(bu)過在結構上(shang)比(bi)較牢(lao)固，因(yin)此(ci)運(yun)用(yong)在輕機(ji)槍(qiang)及(ji)中(zhong)型(xing)機(ji)槍(qiang)等全自動(dong)(dong)(dong)(dong)(dong)(dong)武器上(shang)。