This is what I do all the time and have great success. I use acraglass from brownells. I mix it up spread it out on a piece of cardboard. Do a about a teaspoon full. Heat it up with a heat gun. (one they use to strip paint). It will get real runny and flow into cracks easily. It will dry a lot faster than normal. Another thing I would do on that crack (it looks like the area of the heel of the butt plate). Remove the butt plate and take a 1/8 drill and drill inside following the crack for about 1/4 inch length. Don't let the drill bit come out of the outer surface. Be very careful. Pull the bit out and turn the stock on end with butt up. Then clamp stock to something that keeps that position. HEAT the acra glass up until it gets watery and keep applying it with a small 1/16 dowel down into the drill hole. Let it run down the hole until it's full. Let it dry over night. ANOTHER thing I would just barely shave off some wood in that area where the crack started. There is some stress in that area that caused the crack in the beginning. BARELY SHAVE OR SCRAPE it off. There is more that can be done to hide the crack but that is another post. Basically using artist oil paint and micro dobbing only in the visible crack. After the paint completely dries then apply some light coats of finish. The trick is is to paint only in the visible crack line not on the wood. The paint must match the background of the wood. It takes a lot of time, but that crack can be hidden. I use a fine liner pen (from MOHAWK) to imitate the pores. I guess the main point is after all this, is heat the acra glass and it will get the consistency of water. It will penetrate really deep into the cracks. I hope this helps.
