Hey,
I've had problems in the past getting decent accuracy out of my AR-15. Actually, I've had problems shooting accurately. There isn't a problem with the rifle at all. I've always had moderate groups (couple of inches) at 50 yards, but at 100 yards I was pretty much printing all over the page.
Anyway, I started to feel that I would never be a decent shot, especially reading about the 1" groups and so on that guys here are getting at 100 yards. My "groups" at 100 yards were nowhere near that! The rounds were just all over the page, with no seeming rhyme or reason to their madness. I was desparing some, so I found a post that described basic marksmanship. I don't have the link, but it basically described in detail sight picture, trigger work, breathing, etc.

After reading that post, I realized that I wasn't getting a consistant site picture. I was always looking at the peep from a different distance, and in retrospect, was too far back from it most of the time. I didn't realize I was supposed to, as the post suggested, touch my nose to the charging handle.

I finally shot an excellent(for me!) target this weekend, and I modified 2 things about my shooting: First, I now touch my nose to the charging handle when shooting. Secondly, I used Winchester USA223R1F 55 Gr. FMJ 50 rnd value pack ammo instead of SA surplus. I'm not sure which made the most difference, but I don't think the SA was costing me more then a couple o' inches at 100 yards. (I had basically no consistency before)

Anyway, I can't post a picture of my target, but I'll describe basically what I got. I know this isn't spectacular accuracy by any means, and some people might giggle that I'm happy with it. But I went from horrible to fairly consistant with just a few minor changes in shooting, and since I've seen other complaints of people that are having problems getting decent accuracy, I thought I would post what i was able to get.

The rifle: A Bushmaster XM15 with an A1 rear-site and standard 20" HBAR barrel.
The Target: A standard NRA 100 yard target which has was seems to be about a six inch black "bullseye".
Shoting conditions: Firing from a bench with a sandbag for rifle rest. Iron sites, slow, single shots. (no double taps)

Distance: 100 Yards.

I fired my first four shots which my girlfriend spotted in as missing the target. This made me a bit frustrated, but figuring the trajectory might put it over the target at this range (it was unlikely, being only an inch or two high from POA at 50 yards), I sent another 2 slightly lower. These were about an inch below the bulleseye, and horzontially parallel producing about 1.5"-2" pair.
I then fire 2 more shots in the same vicintiy which produced a 2-2.5" inch pair a few inches over.
I fire a final 2 shots which appeared to again miss the target.
Those rounds which appeared to miss the target, were in fact in the black. The first 4 rounds produced 3 "10" hits, and one "flyer" on the border of 9 and 10 (In all fairness, mostly on the 9). The 3 rounds produce what is probably a 1.5-2" group. The last pair of rounds were on the inside edge of the black, in about a 1.5" pair.

Anyway, now I can work on tightening my groups, and practicing from different positions now that I know how to use the sites better.  I'm quite satisfied with my bushy, and look forward to hopefully one day being a good marksman. What a difference technique and/or ammo can make!

Anote on group size: I have to estimate not having a ruler handy. Most of my "groups" are pairs, and center to center look no more then 1-1.5" , depending on the group. I'm estimating larger then that since that's not an accurate group size. I could be exaggerating those tighter in my exhuberance, and will try to measure them later today.

Welcome to the world of shooting. It only gets better from here. It is great to see young men have enough interest in the spot to teach themselves.

Right on. Shooting is much more fun when you are hitting something, and you will get better with practice.
I have never understood people that shoot just to make noise. Accuracy is the only thing that pulls my chain. You can't miss fast enough to win a gunfight.

I measured the groups.
The 2 shot pairs measured from the outside of each hole came in at:
1.4"
1.75"
~1.9"

The rest of the groups were 2.5-2.6" for the 3 shot(All in the 10 ring, hehehee) group, and about 3.1" if you count the flyer.

Not spectacular by any means, but I'm so excited. I feel like I'm finally hitting something, and can't wait to go back for more.
I guess I'll hold off on that scope until I just can't shoot any better.

And yeah, it's way more satisfying when I have some measurable progress. Or at least a decent target to take home, hehehehe.