Barrel length vs accuracy

[Poor_choices]

Everyone knows the 21 3/4" barrels are the most accurate!

For anyone who doesn't get that reference, look into "Secrets Of The Huston Warehouse".

 

[Scammer122725]

Barrel length doesn't have so much to do with accuracy as it does velocity. In your example, a 6.5CM with a 20" barrel would theoretically be just as accurate as one with a 26", albeit slower.

Edited to add: What "new gun" are you looking at? A 20" barrel length may be all you really need unless you're wanting to handload and experiment with slower burning powders to gain velocity.

 

[Jamie]

Didn't the Houston warehouse experiment come up with 21 3/4" as best length for barrel harmonics? It's been at least 25 decades since the last time I read that.

Sorry....I see someone else posted that as well..

 

[lancetkenyon]

An accurate rifle is an accurate rifle. Barrel length means nothing for precision. Only velocity.
I have 20" barrels that shoot just as accurate as 28" barrels once load work is complete.

I think barrel contour and stiffness are much more critical for repeated shots. I only have 1 barrel that is a 3b, all the rest are fatties. No pencil barrels for me. I will take an added pound or three to a rifle for stability and consistency.

 

[Bullitthead]

Length = velocity
Better quality barrel will generally have better accuracy.
KISS- keep it simple stupid

 

[SmokinCrow]

I'm willing to bet bet its the Nut behind the gun that makes the biggest difference on accuracy. As has been stated barrel length affects more of your velocity, but all being equal length would not affect accuracy.

Now the nut behind the gun will make the difference and the caliber. For Magnum cartridges I shoot much better with longer barreled rifles. I think its a balance thing for me. I feel like I control the rifle better with less muzzle jump. So I am a more accurate shooter with a longer barrel. Non magnum cartridges I don't notice much difference or at least to the degree I notice with a magnum. But I still prefer slightly longer just for the balance and feel of the rifle.

 

[Mikecr]

Didn't the Houston warehouse experiment come up with 21 3/4" as best length for barrel harmonics?

That was for a tiny little 6PPC, FB bullets, and common load/lot of magic N133.
Similar could be determined with testing (and enough resources) for a LR cartridge, and I would think results would differ considerably.

The 6PPC load they used, per QuickLoad, produced only ~6Kpsi muzzle pressure, even while competitive peak pressure would destroy most hunting size cases & barrels. A typical 30-06 with a stupid-short 24" barrel would see twice that muzzle pressure, and possibly generate a dangerous secondary peak in chamber pressure.

 

[Chris F]

I look at this question through the lens of 3 separate but interrelated sides of a triangle; you're balancing velocity, weight and accuracy. Short range Bench resters seek accuracy first and foremost but are bound by weight limits. I don't see any current competitive rifles sporting 24" or longer barrels. Palma shooters need to keep their 308 Win bullets supersonic at 1000 yds and need accuracy though not as much as benchrest. Theyll sacrifice some accuracy to shoot a 30" barrel that still makes weight and can be shot prone with a sling. (It takes 30" to keep that 308 supersonic at 1k). F-class needs more accuracy, and still velocity, but have more generous weight limits. They're allocating their weight budget to heavier barrels that aren't 30" long.

 

[Hobo335]

All this BS make me wish for the return of the BOSS system. Lol

 

[Veteran]

This question is a complex one. It has several facets. One trade off that is obvious is velocity vs. accuracy or group size.
That has been mentioned above. Weight is another that has been mentioned.

LINK:

Finite Element Analysis -- Dynamic Analysis of a Light Rifle with/without a tuner.

varmintal.com

This link just above is to varmintal and the author of this website is a retired physicist from Lawrence Livermore Labs. His name is Al Harral.

He spent his career using finite element analysis models to model explosions and structural reactions. These models divide the structure, in this case a rifle into tiny little cells or blocks and model the the explosions and the pressure and sound, and physics from one cell to the next
cell by cell until the bullet leaves the muzzle.

He modeled a 6 mm rifle in 20, 22, 24 inch with tuners and all the specifics of the bbl. measurements, taper, etc. are listed about half way down on the link page. He found the 24 inch gave the best grouping. He also plotted all the data from an experiment that Richard Lomax did and wrote about where he progressively cut an inch at a time from a .223 bbl. and measured accuracy or grouping. He found the optimum bbl.
length was about 17 inches in that experiment. All the data is presented towards the bottom of this linked page.

Harral shows that the results will matter depending on what powder and burn rate and bullet size is used in a particular rifle.
That just makes sense, and all of this is also tied to barrel harmonics and as we know length, weight, and taper all affect barrel harmonics
and accuracy.

But I think I can generalize just this much.......for a regular hunting rifle of avg. weight, barrel taper, etc. with a scope mounted on it,
likely the best accuracy will be in the 22-24 inch range. One might get slightly better accuracy with a 17 inch barrel, but at the sacrifice of velocity and range. Ie, 100 yard rifle accuracy if that's the goal.

Likely, when one starts shooting magnum calibers with barrels longer than 22-24 inches, one may lose some accuracy due to barrel harmonics.
again assuming avg. barrel taper and weight, all other things being equal. In a magnum caliber with longer barrels, extra barrel diameter, and
and weight would be desireable to compensate for harmonics in order to retain accuracy.

That's a generalization but one that I believe is in the correct direction.

 

[bultinkle]

This is not a dig at OP or at any specific person, just a comment on how I've felt after I've gone down these rabbit holes in the past.

We spend so much more time thinking about how we could theoretically make a pipe more accurate and so little time with how we train to make ourselves more accurate as rifleman. I'd wager the reality as hunters is that the first one is almost never the problem in any missed opportunity

 

[tomcat818]

I consider the following points with regard to barrel length on a hunting rifle:

1) I look for 100% burn rates for more consistent SD\ES which generally means 24+ length barrels for magnum cartridges over ~70 grains.

2) Off hand balance vs muzzle velocity and overall weight.

The weight aspect is divided between length and contour and I prefer medium\ med heavy vs light contour.

Accuracy & precision do not enter the equation when deciding barrel length for me.

 

[Mikecr]

All this BS make me wish for the return of the BOSS system. Lol

BOSS worked great for me.
I still believe it's the best barrel tuning system.

I could focus on powder development and then dial the barrel in.
This, after the prereqs: primers & bullet seating.

 

[biednick]

As far as I'm aware it's largely a wash. Assuming a good shooter, well made rifle, and good load, movement between ignition (when recoil starts) and when the bullet leaves the barrel is the biggest driver of dispersion. All else being equal shorter barrels are lighter so the gun moves faster, but the bullet exits the barrel sooner so it doesn't have as much time to move.

Increased velocity offers slightly increased hit probability at long ranges, so a longer (faster) barrel will increase hit probability on long range targets.