Specialty screws for gunsmiths are available in an assortment or here, as bulk bags of discrete screw options.

Thread Size	Thread Length (measured under the screw head)
	Fillister Head (Type A)	Oval Head (Type B)	Headless Plug Screw (Type C; not heat-treated)
6-48 (.200″ head O.D.)	1/8″, 3/16″, 1/4″, 5/16″, 3/8″, 7/16″, 1/2″	1/8″, 3/16″, 1/4″, 5/16″, 3/8″, 7/16″, 1/2″	1/8″
8-40 (.240″ head O.D.)	1/8″, 3/16″, 1/4″, 3/8″	1/8″, 3/16″, 1/4″, 3/8″	1/8″
10-32	—	—	1/8″