16 inch AR-15 gets 4 inch group at 100 yd with clunky trigger.

[Retro]

I didn't think this was possible. I mounted a 4-12 x 40 Simmons scope on my 14.5 inch barrel/permanent-fixed suppressor (total 16.5 inch in length) DPMS upper/barrel AR-15, and shot a 4 inch group at 100 yards with American Eagle FMJ 223.

The trigger was a 2-stage military version that was extremely stiff and clunky, and the cross-hair was swing back and forth across the entire length of the target when I was attempting to pull the trigger, and I was really impressed by the accuracy despite the horrible trigger and lack of sandbag usage (I used a chair as rifle support).

I can get 3.5 inch with a 20 inch Star Barrel, and I didn't think it was possible to achieve comparable accuracy with a 14.5 inch barrel.

 

[JesseL]

Contrary to popular conception, short barrels are often more accurate than comparable long barrels. The cause of this is the fact that a short barrel is stiffer than a long barrel. It's a common trick for the mini-14 guys to have their barrels shortened to improve accuracy.

I think the basis of the long barrel accuracy myth dates from the use of iron sights that become more precise as the sight radius increases. With optical sights, sight radius becomes moot.

 

[Sniper X]

Some of what you say is true about shorter barrels. In fact, Tactical Operations suggests a 20in on their Tango and Bravo serries sniper weapons rifles as opposed to something longer, especially if the shooter wants to don a suppressor. They GAURENTEE 1/4 minute of angle of accuracy with their rifles if you use FGMM ammo and are a competent shooter. Some barrels depending on twist rate need more like in the 22~24in but with todays powders you can easily get away with 20in on a 7.62mm nato based SWS. On my 16in M4 HB I get about 1moa off the bench no problem with quality ammo so that is not bad at all.

 

[Bartholomew Roberts]

The shorter barrels can definitely shoot, especially if you feed them some decent ammo. AE223 is nice plinking ammo; but it you'll never figure out the full potential of the rifle for accuracy with it.

These two groups were shot with a 16" SS barrel, 3.5x scope and a stock trigger at 100yds. The extra round is where I started to shoot a new group on the wrong target. The grids are 1"x1".

 

[Retro]

Imagine what I can do with a match trigger and sniper 223 ammos...

 

[M2 Carbine]

Retro
I can get 3.5 inch with a 20 inch Star Barrel, and I didn't think it was possible to achieve comparable accuracy with a 14.5 inch barrel.

Very short barrels can give quite good accuracy.

The Kel Tec PLR .223 only has a 9 inch barrel.

 

[Retro]

Then my question is what is the point of making a 20 inch barrel? Just so that it has a + 70 - 100 FPS increase...??? Accuracy is certainly not an issue.

 

[kcmarine]

Don't really know. I mean, sure, the speed increase could be helpful in knockdown power downrange.


Is it possible that the longer barrels have more surface area, and therefore can cool off faster?

 

[M2 Carbine]

The ultra short barrels do get extremely hot very fast but a big reason for the longer barrels is for higher velocity.

For instance the same ammo that will give about 3,300 fps in a 20 inch barrel, will do about 2,900 fps in a 14-16 inch barrel and 2,500 fps from the 9 inch PLR barrel and under 2,300 fps from a 7 inch Bushmaster Carbon 15 barrel.

 

[kcmarine]

One more thing.

These smaller caliber weapons do depend on velocity for lethality. If those high speeds don't exist in a .223 weapon, than the round's effectiveness is reduced. I guess that's why you see the 26" barrels on the Remington 700 SPS Varmint. It's not that the barrel is needed to shoot accurately, but instead the extra length increases the round's power.

 

[another okie]

Some reasons for the longer barrels:

1. Some bullets require a certain velocity to expand or tumble. Without that threshold they just make an "icepick" hole unless they hit a bone. Manufacturers often test with longer barrelled guns because they want high velocity figures.

2. Shorter gas systems on AR type weapons are in general not as reliable as the longer gas systems. Of course, the world is full of reliable short barrelled ARs, but the general rule holds true.

3. Long distance shooting - it's nice to hold on to as much velocity as possible.

4. Many people do still shoot ARs and other rifles with iron sights.

 

[aspade]

Shorter barrels have much higher muzzle pressures that much closer to the shooter's eyes and ears.

That 9" Keltec makes me wince just looking at it.

 

[M2 Carbine]

aspade Shorter barrels have much higher muzzle pressures that much closer to the shooter's eyes and ears.
That 9" Keltec makes me wince just looking at it.

Why do you say that?