You guys need to listen to Gary. A plan is the wrong way to build a longrifle. It will just lead to a mess. I know, I tried to do it that way with the first rifle I made over 30 years ago. It was a rookie mistake. I remember that my grandfather tried to tell me building a gun from a book wouldn't work, but I thought I knew better.
You stock around your parts. THEY dictate most of the dimension. The only thing you need from your plan or photo is the profile of the comb and toe. That is really the only place that you have some wiggle room in the stocking. The width and height of the stock at the lock panels will be dictated by the barrel and lock. The dimensions of the forearm will be dictated by the barrel and ramrod. The wrist will be dictated by the lock panels (barrel and lock) and by the butt piece. The butt piece is located relative to the barrel and lock/trigger based on your desired trigger pull, drop, and cast-off (or in you case being a lefty, the cast-on). You lay everything out on the squared up stock blank. The plan you draw on the stock blank is the only plan you need. I will tell you right now that NOTHING on the finished gun is going to be perfectly, straight, square or plum. I am willing to bet that your barrel isn't even perfectly symetrical and that will throw off all your best laid plans. You measure a few things, but mostly everything is done by eye, and you have to be looking all the time from different angles and with different light. Feeling will tell you as much or more than looking. Of course, for all this to work right, you have to know what a proper longrifle looks and feels like. A plan will not do that. You have to handle a lot of original guns and study them closely. Picture will help some, but they will not replace having the gun in your hands.
Mark E.
