ствол із чотирма нарізами в каналі
four-cycle / four-stroke
four by four
fingertip formation / finger-four formation / four finger formation
barrel groove
barrel assembly (barrel group)
automatic heavy barrel rifle / heavy barrel automatic rifle
slot-type groove
spiral parallel groove
breechblock-stop groove
cam groove
circular groove (of ammunition)
crimping groove
dismounting groove
vertical oil groove
extraction groove
extractor groove
finger groove
groove for coupling
groove
four-point barb
four-charge gun
four by two
four-barreled anti-aircraft gun
four-point
four-stage compressor
four-way valve
four-wheel drive
four-wheel drive truck
four-boss breaker cam
four-stroke cycle
four-step stand
four-stroke engine