Hi,

Generally speaking, if there was a complete upper assembly from the same manufacturer with the same specs, except that one had a 16" barrel and the other a 20" barrel.  Would the 20" upper be more accurate or would it just have more velocity?

Right now, I have a model 1 kit with a chromoly 16" bull barrel and was able to get between 2-3" 5-shot groups with standard trigger, American Eagle ammo & aimpoint ML3 @100yds.  Am wondering if the same with a 20" barrel would improve accuracy.  I am also working on getting a 2-stage NM trigger & reloading in the near future.


-Kenny

IMHO, some magnification helps when you're shooting for groups.  

Quoted: IMHO, some magnification helps when you're shooting for groups.

the world's best scope doesn't make the rifle inherently more accurate.
put your money into the barrel, trigger, finding (or loading) compatible ammo, and range time.

ar-jedi

Quoted: Quoted: IMHO, some magnification helps when you're shooting for groups.   the world's best scope doesn't make the rifle inherently more accurate. put your money into the barrel, trigger, finding (or loading) compatible ammo, and range time. ar-jedi

No but it helps the shooter which is where 95% of the accuracy comes from

If it were me I would try a box of Federal Gold Match rather than the American Eagle.  AE is good ammo but I think that you could reduce your groups with the Gold Match.  As a fyi-if you are getting 2 to 3 MOA with a field grade AR you are not doing bad.

Quoted: Quoted: IMHO, some magnification helps when you're shooting for groups.   the world's best scope doesn't make the rifle inherently more accurate. put your money into the barrel, trigger, finding (or loading) compatible ammo, and range time. ar-jedi

If I'm shooting prone or from a bench, shooting 5 shot groups to check for accuracy and my goal is to see how good my rifle can shoot, taking the "shooter" out of the equation as much as possible, glass is almost a necessity for me.  YMMV.  

An aimpoint dot is 2 MOA or bigger.  It's already covering 2" of the target, or more, when viewing with your naked eyeball.  When I use my 9 powered scope at 100 yards, it does not completely cover a 1" orange sticky.  Meaning my cross hair is smaller than 1 MOA Therefore my fine adjustments are much easier to see and make while pulling the trigger.  

You may not need it, but I need all the help I can get, if shooting for groups and trying to find out accuracy is my goal.

2-3 MOA at 100 yards with an Aimpoint is not really bad at all.  I don't usually get better than 2-3 MOA using irons.  I've gotten a few smaller groups with just the irons, but they are rare.  But with a scope, 1 MOA and better have been achieved quite a bit.

But you probably get 1 MOA with your aimpoint offhand, eh?

Quoted: You may not need it, but I need all the help I can get, if shooting for groups and trying to find out accuracy is my goal.

scroll back up and consider what the OP's question was.  
now return here.
to remind you, he asked whether a 20" barrel was more accurate than a 16" barrel. to wit:

Generally speaking, if there was a complete upper assembly from the same manufacturer with the same specs, except that one had a 16" barrel and the other a 20" barrel. Would the 20" upper be more accurate or would it just have more velocity?

in response to someone's post, i said it would not matter which optic you had.  
you said a good scope will help groups.

so i ask you now to follow along, so we can answer the OP's original question.

step (1): obtain 20 rounds good quality match ammo.
step (2): put rifle w/ 16" barrel in ransom rest. fire 10x for group size.
step (3): put rifle w/ 20" barrel in ransom rest. fire 10x for group size.
step (4): measure groups.  
step (5): come to conclusion.

notice absence of a shooter's influence, and no optics.

now then, how the heck does attaching an optic, any optic, increase barrel accuracy?  

the OP did not ask how to make the overall system (shooter/rifle/ammo) more accurate.  he asked whether a 20" barrel is more accurate than a 16" barrel given the same input conditions.

q.e.d.

ar-jedi

I like shoot rifle length Irons

My LMT 14.5 M4`s are just as accurate or more  as my 20inch HBAR Bushmaster

the ammo selection helps alot BlacK Hills 68 to 77gr or federal 69/77gr

Quoted: Quoted: You may not need it, but I need all the help I can get, if shooting for groups and trying to find out accuracy is my goal. scroll back up and consider what the OP's question was.   now return here. to remind you, he asked whether a 20" barrel was more accurate than a 16" barrel. to wit: Generally speaking, if there was a complete upper assembly from the same manufacturer with the same specs, except that one had a 16" barrel and the other a 20" barrel. Would the 20" upper be more accurate or would it just have more velocity? in response to someone's post, i said it would not matter which optic you had.   you said a good scope will help groups. so i ask you now to follow along, so we can answer the OP's original question. step (1): obtain 20 rounds good quality match ammo. step (2): put rifle w/ 16" barrel in ransom rest. fire 10x for group size. step (3): put rifle w/ 20" barrel in ransom rest. fire 10x for group size. step (4): measure groups.   step (5): come to conclusion. notice absence of a shooter's influence, and no optics. now then, how the heck does attaching an optic, any optic, increase barrel accuracy?   the OP did not ask how to make the overall system (shooter/rifle/ammo) more accurate.  he asked whether a 20" barrel is more accurate than a 16" barrel given the same input conditions. q.e.d. ar-jedi

I was referring to this part of his post:

Right now, I have a model 1 kit with a chromoly 16" bull barrel and was able to get between 2-3" 5-shot groups with standard trigger, American Eagle ammo & aimpoint ML3 @100yds. Am wondering if the same with a 20" barrel would improve accuracy. I am also working on getting a 2-stage NM trigger & reloading in the near future.


-Kenny

He already got the answer about the barrel length from New ARguy and Steve.

He's basically wondering how to get better groups.  And my answer has nothing to do with barrel length.  

all other things being equal, the shorter the tube, the more accurate it tends to be.

this is because the length/diameter ratio is smaller and makes it think it is a stiffer tube. all other things being equal, that is...

Although you didn't ask this, I want to add anyway.

Not only does barrel length NOT affect accuracy, neither (alone) does barrel diameter.

That big heavy chunk you're shooting won't be any more accurate than a QUALITY barrel of significantly smaller diameter and less weight.

I would definitely suggest that you DO replace your barrel, BUT I would replace it with (depending on your funds) either one of ADCO's 16" SS mid-length Recon barrels, a GTS Recon barrel, or a Sabre Defense 16" SS fluted midlength.  

Perhaps not so coincidentally, the barrels cost more as you go up the list while weighing less as you go up the list.  All show about the same accuracy potential.

Technically, a shorter barrel should be slightly more accurate (all other things being equal) as it is stiffer.

Here is an article by Daniel Lilja explaining this:  www.riflebarrels.com/articles/barrel_making/rigidity_benchrest_rifles.htm.  It is pretty technical, but has many interesting observations.  If anybody knows about what makes a rifle accurate, it is Lilja.  There are some other good articles about accuracy on Lilja's site if you poke around.

Here are some excerpts from the article:

While there are a number of factors that determine the accuracy of a rifle barrel, one of the more critical elements is its stiffness or rigidity. Obviously the larger in diameter a barrel is, the stiffer it will be. Almost as obviously, as the length of a barrel increases it becomes more limber. .. When a cartridge is fired in a chamber, the barrel undergoes many stresses. It begins to vibrate when the firing pin starts its fall and these vibrations increase dramatically from then on. During recoil and while the bullet is still in the barrel, the barrel will whip vertically. This happens because the thrust axis of the rifle is above the centerline of the stock. During recoil the barrel comes back and up. The muzzle will lag behind the rest of the barrel in this movement and the vertical whipping motion is set up. While these vibrations of the barrel are very small, they do exist. The stiffer a barrel is, the less the muzzle will jump around.

The best barrel will be short and fat.  Barrel width has more of an effect on barrel stiffness (and therefore accuracy) than barrel length.  So a long but fat barrel will be more accurate than one that is short and skinny.

All this leaves aside the issue of sight radius for irons and the quality of the barrel.

Quoted: Although you didn't ask this, I want to add anyway. Not only does barrel length NOT affect accuracy, neither (alone) does barrel diameter. That big heavy chunk you're shooting won't be any more accurate than a QUALITY barrel of significantly smaller diameter and less weight. I would definitely suggest that you DO replace your barrel, BUT I would replace it with (depending on your funds) either one of ADCO's 16" SS mid-length Recon barrels, a GTS Recon barrel, or a Sabre Defense 16" SS fluted midlength.   Perhaps not so coincidentally, the barrels cost more as you go up the list while weighing less as you go up the list.  All show about the same accuracy potential.

though I feel pretty sure your first statement is incorrect, I'd like you to further explain it if you would.

it seems counter to all I have come to understand regarding "repeatable accuracy" in a rifle and I'd be interested in learning the basis of your opinions...