The best people to ask are McMillan!!
I've had about 16 units come in this year, basic units non adjustable with little hardware 4-6 months, all others like USMC spec A4s with all the options etc 8months give or take. It is what it is!!!
Plan on 8 months for a McMillan!!
Is this based upon recent personal experience? If so I even happier that I went with Manners.