Barrel length and accuracy

[ZekeLuvs1911]

Hi all,
I have a question. I always thought that the longer a rifle barrel is the more accurate the rifle will be. I know that some accuracy is dependant on the shooter, cartidge, etc....but I was told by a salesguy at the gunstore that it is a myth that the length of the barrel has anything to do with accuracy. He said that you could have a 11.5" barrel vs a 20" barrel on a rifle and it will make zero difference. What do you think? Thanks!

 

[444]

The salesman is right.
The only effect the length of the barrel has on accuracy is that it allows you to have a longer sight radius. So, if you are shooting with iron sights, it makes it easier to shoot the rifle accurately: but the rifle itself isn't more accurate. It is just easier for you to shoot it accurately.
In fact, a shorter barrel is more accurate because it is stiffer.
This isn't just speculation. It isn't a matter of guessing or talking about opinions.
The most accurate rifles in the world are used for benchrest competition. All you have to do is see what they are using.

 

[Feanaro]

All other things being equal barrel length doesn't improve accuracy that I am aware of. Now, lost velocity will make the bullet drop faster but it won't actually make the firearm any less accurate, assuming you adjust.

 

[DMK]

What about velocity?

Longer rifle barrels allow the powder charge to increase velocity (up to a point of course). Does velocity affect accuracy either way? I'd think that the increased velocity would make the ballistics flatter and this would be a benefit for longer distances, wouldn't it?

 

[444]

A "flat shooting" rifle is another thing that allows you to shoot the rifle and hit targets easier: but it doesn't do anything for the accruacy of the rifle.

Not that I am an expert or anything, but maybe we should first define the term accuracy.
Accuracy is the ability of the rifle to put one bullet on top of the last bullet. It is consistency. The ability to fire a tight group.
If you have accuracy, hitting the target is a matter of adjusting the sights and your shooting skill.


An example might be: You have rifle that fires a cartridge that drops eight feet at 500 yards with a 100 yard zero. But, it will put every shot into a group of four inches at that range.
You might have another rifle that fires a cartridge that drops one inch at 500 yards with a 100 yard zero and will group all it's shots into a two foot circle at that range.
If you were to fire both rifles at a target, odds are you would hit more, and come closer more often with the second rifle. You don't have to be a good judge of distance. You don't have to know the sight dope for the rifle. It will hit close to the target if you do your part. BUT, the first rifle is actually the more accurate of the two rifles. The cartridge it shoots makes it harder to hit the target, but the rifle itself is more accurate.

 

[Swampy]

Ditto what 444 sed.

Swampy

 

[DMK]

Accuracy is the ability of the rifle to put one bullet on top of the last bullet. It is consistency. The ability to fire a tight group.
If you have accuracy, hitting the target is a matter of adjusting the sights and your shooting skill.

Good point. That's why they make adjustable sights.

I guess I was thinking about stability. If you pushed the same round a little faster with a longer barrel vs. a shorter barrel where you just adjusted the sight for the steeper arc. Would it be more stable at distance or would it not matter? I was probably just way over thinking this.

 

[JohnBT]

Another definition of accuracy is the ability to put the first shot where you want it.

There're a lot of longer, thinner barrels with tuners in rimfire benchrest. A long rimfire barrel helps keep the target ammo from going supersonic and ruining accuracy (it's not the going supersonic that's the problem, it's the bullet returning to subsonic speed before reaching the target that throws it off.)

Happy New Year!!!!

John

 

[Fumbler]

In addition to what everyone has said, shorter barrel are actually more accurate than extremely long barrels.
You don't see benchrest shooters with 36" barrels out there.
A shorter barrel deflects less than a longer one with the same amount of force applied to them.
It's kinda like waving a piece of 1" diameter PVC that's 5 feet long versus one that's 8 feet long.
A shorter barrel, because it deflects less, will be slightly less ammo sensative and managing the harmonics through reloading will be slightly easier.
The differences are very small, it really only matters to precision benchrest shooters.

 

[ClarkEMyers]

I think the salesman is more nearly right but...

That is to say longer is more accurate is not true for many cases. The centerfire benchrest discipline has demonstrated again and again that for the same weight short and stiff beats long and whippy - even unlimited rail guns don't run to super long barrels. For position shooting shorter barrel time might be the choice hence the bloop tube. For .22 pistols Gun Digest reported a test that found short and stiff was the way to go - others might find a long barrel easier to shoot or more likely to carry the power to knock over silhouettes down range. The success or lack of it that Browning showed with their BOSS system shows that barrel vibration and tuning is poorly understood after all.

On the other hand lower muzzle pressure has been found to be an accuracy enhancer in many tests - seems likely a really short barrel with high muzzle pressure won't do as well and lots of people say this is borne out by shooting snub nose revolvers against longer barrels. Even a pellet gun might have a vent to reduce gas pressure behind the pellet once the pellet leaves the bore. A Palma rifle will have and need a long barrel to keep a non-magnum .308 target load supersonic to 1000 yards - don't try this with a T/C pistol even in .308.

So I'd say the clerk is mostly right with exceptions and within reason longer has no advantage - frex I hunt with a Scout and find it accurate enough.

 

[schromf]

My comment is check out Dan Lilja's website. Look in the articles and he has a write up on this, which is very detailed with math formulas.

Long Barrels droop, but short barrels loose velocity.

The reason you don't see many 36" barrels is most barrel makers don't have a lathe with a big enough bed. You have to look to get longer than a 32" barrel. Remember 2" is lost on barrels, 1" to threads and all good gunsmiths cut 1" off the muzzel end of a barrel.

 

[Preacherman]

As for velocity, remember that the round itself dictates the optimum barrel length for the propellant available. For example, in .22 LR, it's widely accepted that a 16" barrel is the optimum length for velocity: longer than that, and the bullet actually begins to slow down, due to drag forces on the bullet being stronger than the pressure generated by the relatively small gas volume. In the same way, any small-case round will usually shoot to a lower velocity than a high-capacity case round, because there is only so much room available for propellant. (Of course, one can experiment with different burning rate propellants, so as to maximize their effectiveness: but if a case can hold more propellant, for a given weight of bullet, it'll probably produce a higher velocity). So, one has to "tune" barrel length to the available propellant to produce the best possible velocity for that round.