The answer to which grain weight is best depends on the type of shooting and which firearm you’re using. Here are some various applications and their recommended grain weight:n 1. Routine Range Shooting nUnderstanding grain weight isn’t as important when first becoming familiar with various firearms. For beginners, there is a standard size and grain weight for all ammunition types and brands. For the range, the 55 grain for AR-15 and other 5.56/.223 rifles are adequate because you will aim at targets positioned in short to medium distances.n 2. Hunting nYou generally want heavier grain weight to deliver more energy into the game, but this may also depend on animal species. Hunters who do not want to leave blood trails, meaning they prefer a more humane shot that drops the game on the spot, will go for heavier grain. A heavier grain also means that they may have to do more stalking to get closer because heavier cartridges travel slower.n 3. Self-Defense nSelf-defense situations typically occur at close ranges of at least 21 feet from the threat2. Should you need to engage a threat, you want the stopping power that heavier rounds provide. While considering round weight and energy, you should choose rounds that are less likely to pass through a target, which means lost energy and additional hazards. Even though self-defense rounds are commonly more expensive, you should practice shooting these at a range to ensure they feed and fire without malfunction in your firearm, and to familiarize yourself with how they shoot.n 4. Marksmanship nSport shooting of rifles at longer distances may require lighter grain ammunition. Other factors, such as wind conditions and the type of rifle, should also be considered.