Well on eblades and 05egos its a 10-32 UNF thread holding a rail on with either a Button, Cup or countersunk head depening on the rail, probably the same for others but im not 100%
Well on eblades and 05egos its a 10-32 UNF thread holding a rail on with either a Button, Cup or countersunk head depening on the rail, probably the same for others but im not 100%