I'm relatively new to home brewing. I've had some training at a local brewery as an intern. I'm not going in completely blind, but I'm no professuh. About 6 weeks ago, I made my first all-grain batch. That was a bit of an experiment in terms of putting what I know to use with full creative control, and learning how my equipment behaves. I went with an oatmeal stout because it's a forgiving style (from my understanding). My target OG was 1.065 and I wound up with 1.062. I had considered this fairly close, but I wound up with 4 gallons at primary fermentation when calculations were done for a 5.5 gal batch. Today, I had went for an American IPA and had similar results. My target OG was 1.071, wound up with 1.071 on the money, and I finished with 4 gallons in the carboy with an anticipated 5.5 gallons. It appears I am doing something where I consistently hit my targets, but lose quite a bit of volume. My question is mainly why that is and how do I maintain both the anticipated volume and sugar concentration? Am I a victim of dumb luck? It seems to me that if I were to be losing a gallon and a half it would be during the boil, then I would be increasing the wort's density relative to water. Thanks a ton.