Can anyone give me a ballpark estimate of how accurate an AR-15 with a Bushmaster 20 inch National Match heavy barrel should be?  No brake, no compensator, no flash hider, with standard A2 fittings.

How much of an improvement can I expect if I go to a free floating barrel tube arrangement instead of the A2 hardware?

I am of course referring to the gun's accuracy, not the shooter's.  

CJ

What kind of accuracy are you looking for?

I don't see any reason why you couldn't get 1" groups out of it with decent ammo. Hell, I've got 1.25" groups with iron sights at 100 yards out of a FN Government Profile upper.  And this is just a GI grade upper, by no means a match grade rifle. AND I did this three times in the same day with SURPLUS ammo.


If you call Bushmaster, they'll tell you that any of their rifles will shoot 1" at 100 yards out of the box. I don't doubt it. With a match model, I'd think it's up to you.

AS Seamusmcoi noted 1 inch would be what I would expect. Changing to a free float system will improve it some,maybe 1/10 of an inch or so from sand bags. Depends on what you use the rifle for. If you use a tight sling the free float will improve the groups alot.

I have witnessed a marksman use my BM SHORTY (16inch total, 14.5 inch barrel, 1.5inch brake, I believe) put 5 rds under 1moa at 200yds with iron sights only.  Three of the five overlapped like a three leaf clover!  The Shorty does NOT have a free floating barrel or match anything...I would imagine your National Match would do just as well or better in the right hands.

He used reloaded Nosler, 55gr, red tipped ammo & also some 64 grain, Winchester (I think) factory ammo.

Amazing rifles...mine has not had any work done on it like trigger work or Jewel trigger, etc.  This is right out of the box.  I thought I was having trouble with it since MY accuracy had gone to crap but with good ammo & the right shooter the results are inspiring!

Good to hear this.   My hopes are to get that kind of accuracy out of this rifle.  

Actually, I'll have two rifles shortly.  One of them is being built on a Bushmaster complete lower receiver,  and the other is being built on a lower receiver I just got done milling from a 0 percent forging.    One gets a Colt SP-1 upper (post-ban modified) that has had an offset bushing permanently installed in the large front lug so no offset pin is required, and the other will get the 20 inch NM heavy barrel on an A1 upper.    I'll mix and match the two uppers on the two lowers and if I'm lucky, upper A will work best with lower A, and upper B will work best with lower B.    I might guess that the Bushmaster barrel will end up on the Bushmaster lower, but only time will tell.    The heavy barrel rifle will be the one that gets the 3-9x50 scope, assuming it's the more accurate rifle.

At the moment, 200 yards is the longest range facility I have readily available to me, but that may soon change and I'll have access to a private range with up to 600 yard facilities.

CJ

I have a Bushy M4/16" barrel and it is extraordinary. 1.5" groups at 100 yards, with iron sights and crappy ammo. I'm sure I could do better, but I'm more into consistant combat-shooting instead of target practice. I'm sure with a 20" match-grade rifle, you could work miracles as far as accuracy.

The trigger will be the biggest obstacle to accuracy.  I have never been able to get under 1" MOA, and just barely that, with either of my Bushmasters and the JP single-stage trigger adjusted to 4 lbs.  Of course all I have loaded up so far have been 55 grain Remington bullets.