This is a good time to discuss drawing cross sections. I will start with the grip portion of the forearm, but the process for other areas is very similar.
We start by laying out in the square what is already there. The dimensions were determined in our original plan. I took a short cut by tracing the octagon from a spare piece of barrel. Pretty obviously, our profile has to fit inside of this layout, but that still leaves room for lots of possibilities. A main resource for me is a group of 11 rifle drawings of southern rifles. These are Southern Originals 1 (5 prints), Southern Originals 2 (5 prints) and the Hershel House Foxfire Rifle (not an original, but I like it and it has seven cross sections). These are available from the Log Cabin Shop. I refer to them repetitively; it is nice to have one drawing, but with several you can compare different ways of doing the same feature. For chunk gun fans Originals 1 has a drawing of the best known old chunk gun, Old Scaley.
In keeping with the spirit of this project, the cross sections are going to be kept towards the plain and simple. We are going to generate the curves with drafting templates, so even the drawing impaired should have no trouble. The first curve is a goodly(1/16" radius) radius to the side of the barrel. We do not want the wood tapered to a thin point on a chunk gun as this area provides the base for our shader. I actually thought about leaving a flat at the top of the stock, but decided that was just going overboard.
One of the things that I notice about longrifle contures is that there are few true radii, but many of the curves seem to be segments of ellipses. An ellipse is a curved line in which every point is equally the sum of the distances from two points. The common method for schoolboys and craftsmen to generate an ellipse is to drive to brads, make a loop of string to go around them and hang a pencil in the loop. By varying the length of the loop and the distance between the pins limitless variations may be produced. Fortunately for me, I have three different ellipse templates which handle most of my needs. The specific ellipse that I am using here is 1.750" from a 45 degree template (I honestly do not know what degrees have to do with describing ellipses). I think you can see that we skew the template to get a pleasing line that contacts the 1/16" radius and the bottom center point of the stock.
A couple of things to point out, we are drawing on card stock and we do NOT draw on our original layout, we make copies of our original layout (also on card stock) and work on them. Not only does this allow us to make more than one variation, but the same layout will be used for the cross section of the forward forearm and the stock nose area.
The cross sections have two purposes, they help us envision where we want our conturing to end up and they provide templates for us to make form scrapers if we like. For the scraper templates, we make a copy of our cross section and cut it out with an Exacto knife. I will show you the scrapers that I make out of junk hand saw blade when they are done.