Acraglass is off white but has a strong stain that comes with it. With the gap you are describing it won't take a teaspoon full. MAKE SURE that you use release agent on any surface that might get glass on it and I always cover the threads(male & female) on the through bolt. Go easy with the stain, add tiny amounts until you get a match. For a hard working gun I use poly cut with mineral spirits (20 %) and just wipe the numerous coats on. This is not a classic finish but it is tough.
bill