Hello everybody I'm new here so bear with mehowI got free float and muzzle break from Armalite and bipod from Harris:
http://i99.photobucket.com/albums/l314/honohessu/DSC00026.jpg
The scope is IOR MP8 2.5-10x42 and is mounted with SAKO optilocks.

Then I tested couple of ammo:
55 grain AE from 165yards (150meters):
http://i99.photobucket.com/albums/l314/honohessu/DSC00035.jpg
Those are centimetres NOT inches!

Then 69 grain S&B match also from 165yards:
http://i99.photobucket.com/albums/l314/honohessu/DSC00032.jpg
That's .9 MOA
So S&B it's for meheadhttp://i99.photobucket.com/albums/l314/honohessu/DSC00001-1.jpg

The speed difference with S&B was only +/- 2,5m/s or 8ft/s which is incredible from factory cartridge.The average was 900m/s or 2950ft/s from 20" barrel. I also measured 3 times more expensive Federal Match cartridge speeds. The difference was 30m/s or 100ft/s! And it didn't perform as well as S&B so I went with S&B.

So we headed to the long range and here is the shooting:
550 yards:
http://i99.photobucket.com/albums/l314/honohessu/DSC00009-1.jpg
The five holes on the left is from my friends TRG 338 Lapua mag and the four on the right is from my AR. One got away I believe to right as we see here at 650 yards:
http://i99.photobucket.com/albums/l314/honohessu/DSC00011-1.jpg
Those are still centimeters! Only three holes. Two went by from the right but they were extremely hard to spot.

So I adjusted the scope and here is the result (still from 650 yards):
http://i99.photobucket.com/albums/l314/honohessu/DSC00010-1.jpg
Again only 4 holes. There is much more vertical difference than horizontal. I guess that is because of the shooterhichhttp://i99.photobucket.com/albums/l314/honohessu/DSC00007.jpg
See how the targets are bended!

Finally I shooted at 750yards to target which indicated with light if you hit them. The area which it measured was horizontally about 14inches and vertically unknown. About every fourt shot went by.
Just to compare my friend shot also from 750yards with .223 SIG with Meopta 1-4 x something (I didn't look but it wasn't any long range scope). He shot 55 grain AE and 62 grain WOLF. He shot about 60 round and missed them all.

That's about it. There's coming lots of new parts to my Bushmaster: gas block (the current front sight makes the aiming hard), new free float, picatinny rails, trigger, charcing handle etc. Then we take a second roundhave

This is America and you are shooting an American rifle, therefore all groups are measured in inches.  Remember......2.54cm = 1 inch.

Only joking with you.  Enjoy shooting your AR in Finland.  Welcome to the BRD (Black Rifle Disease).

Good accuracy for the rather extreme distances you were shooting with "factory" ammo.  Much experimentation with different loads in your rifle could result in some improvement.  A good, solid steady rest instead of the Harris bipod would help too.

Wow!  Nice shooting there and a great looking rifle!  

I'm still trying to convert the centimeters to inches though....

The farthest that I've shot my rig on paper is 300 yards, but I want to push it out to 500-600 one of these days.

I think you're doing pretty well at the distances you're shooting.  If it is a relatively calm day I'll take my .223 out to 1,000 yards.  Have not done it very often but it sure is a challenge.  

Welcome to the board, and great 1st post.

That is very good shooting, I am surprised the S&B ammunition shot that well.
Shooting further than 500 yards with an AR-15 is a real challenge IMO, but also a lot of fun. Here are a couple pictures of a 600 yard range I set up.

Rifle: Mk12 Mod0'ish.         Scope: Leupold Mark 4 LRT 3.5-10x40 with M1 turrets.


What 600 yards looks like from across the valley. Target is to the left of the bottom cluster of trees.


This is what a 12"x10" target looks like at 600 yards through the Leupold at 10x.


First three shots of the day. Still the best 3 round "group" I have had with a cold bore at that distance. Ammunition was Black Hills 77gr. BTHP which is the most accurate factory ammo I have shot.

I would recommend looking into reloading your own rounds.
I have been able to cut my group sizes in half once i found a load my rifle liked.

As you said if that is a 10 inch X 12 inch plate at 600 yards

Damm good shooting.

I wouldn't stand up and give you the finger at 600 yards.    

Quoted: Yes the S&B shoots the best "group" with my gun. I've tested AE 55 and 62 grains, 55 grain Remington, 69grain Federal Gold Match and the 69 grain S&B Match. The average "group" with S&B is about 1MOA (5 shots at 150meters or 165 yards) so that is about 1,7inch. Here in Finland we don't have Black Hills ammo What kind of group your gun does from shorter distances?

I seldom try to shoot really small groups, as long as a rifle will shoot MOA I am happy.

With that rifle some of the best 5 round groups I have shot have been right around .75 MOA with Black Hills 77gr. BTHP and with my own loads using Nosler 77gr. BTHP and Varget.

nice grouping

Very nice shooting, considering it was S&B ammo and you have a standard factory barrel.

55grn FMJ is really not the best ammo at distance. If you want to reach 800 meters with reasonable accuracy, you need to reload your own ammo.

I've shot Hornady 75grn HPBT factory loads out to 750 meters from a 18" barrel with 1/8" rifling. All keyholed on the target, but a 10-shot group still measured about 17" in diameter. At 600 meters the bullets were still stabilized and made nice round holes. A 10-shot group at that range measured 10", which was better than I expected. The 75grn HPBT has been the best shooting bullet for this barrel that I've tested out to 300 meters, so hand loading with this bullet would probably provide excellent results. I intend to start reloading within the next 12 months, so I can get the most out of my rifle.