Seperate the upper and lower.
Remove buffer and spring.
Remove screw from rear of butstock.
Remove stock. (take it off slowly so you don't lose the rear takedown pin detent and spring)
Remove spacer.
Unscrew buffer tube. (Watch the buffer retainer and spring)
Screw the castle nut all the way onto the threads of the carbine stock, and make sure the receiver plate is on there and facing the right way.
Screw in the carbine buffer tube until it is almost to the post on the buffer retainer and is in the correct position.
Put the plate against the rear of the receiver making sure the detent spring goes in straight.
Screw the castle nut up against the plate and tighten with a stock wrench.
Put the CARBINE SPRING AND BUFFER in. DO NOT use the rifle spring and buffer from the A2 stock.
Put the upper and lower back together.