A question for you, if you were showing somebody how to use a pistol, would you have them worry about the actual point of impact or the grouping? It's the grouping that's important, yes?. The sights can always be adjusted to change the point of impact. If that same person had a wide grouping or as you say, a mess, what would you suggest to them. Perhaps, as in the "old corps" expression, they are "chasing the bull"? You may want to use what you know with pistols, by way of grouping, to your rifle. Massbites expressed that first I believe in not so many words along with indexing. You may want to start off on a bench rest, which is just a simple support that goes under the stocks/fore ends, not the barrel. You can buy one or make one. A number of people use sandbags. Draw on your pistol experience for aim, breathing control, trigger hold. A suggestion for you: do not rest your beak on the charging handle. At some point, the charging handle may catch the bolt on the rebound and cause you a mischief. I let mine touch the knuckle of the thumb thats grasping the butt stock, not just on AR's but all rifles. I suggest using a bench rest as a way of determining if it's you or what was mentioned a couple of times before about the indexing. I have a feeling that it may be your newness to rifles. The only addition to what your used to on pistols is what's referred to as cheek weld. That just means a consistent way of how you hold the rifle up against your cheek. If you determine that the rifle is fine by this method, or your groups start to shrink to a nice small pattern, you can adjust the sights to your eye. Again, as in pistols, worry the groups at first, not the poi. Depending on which XM you have, A2 or A3 (one goes to 800, the other 600), there is a difference on the settings. No biggy really, you can look it up on the web for the alts on how to zero. If you can't get it, just say so and I or others will explain it. The thing that no one has mentioned to you is that in the off hand, kneeling and sitting positions, you may want to employ what is called a hasty sling. The idea is that it holds the rifle tight to your shoulder, using your upper arms and shoulders, not the lower parts of your arms. I know when I have a good one is when I can hold the rifle by no more then the pistol grip and it's rock steady. Fortunatly for me, my carry length is the right length for a hasty so I can go straight to the ready by rolling it off of sling arms to a fireing position. You can look up hasty slings on the web also. I couldn't explain it by typing, but I could show you FTF but that's not possible. On the prone, you will be resting on your elbows and that should be good enough for support. Your body should be around 30° offset to your aim. For range work, get either 10 or pre-ban (if that matters in your state) 20's. 30 rounders aren't all that hot for the range. They are more in the way than they are worth.