Re: How to retrofit a BDC/Turret
What Rob said.
At distances where the BDC will be accurate irrespective of environmental conditions, you can easily memorize your dope - or just print it small, and attach it to your stock, or attach it inside your rear scope cap.
At longer distances, you will have to take variations in atmospheric conditions into account, and the BDC won't be accurate.
Save your money to spend on ammo and training.