The BT 100 with Thumbhole stock is a little different to remove the stock from conventional stocked BT 100's. The stock bolt runs from the grip cap up to an adapter piece in the back of the receiver. To remove the stock, you first remove the screws holding the grip cap on. Then under the cap will be an Allen head stock bolt. You remove it and the stock should come off. To replace with a conventional stock, you must first unscrew the adapter piece from the receiver. Then you will need a regular full length stock bolt to go with the conventional stock. This stock bolt will thread into the hole where the adapter piece was removed.