View Full Version : optimum barrel length
December 31, 2006, 02:02 PM
optimum barrel length, relative to accuracy, for 308 and it's family, 243, 260, 7mm-08, 338-08 & 358
December 31, 2006, 02:08 PM
There was a benchrest shooter-gunsmith who concluded that the single most accurate barrel length was 21.75". I don't know whether that applied to cartridges larger than the .22s and 6mms he usually worked on.
December 31, 2006, 03:23 PM
A longer barrel length will always give more velocity, even up to rediculus lengths like 35". For benchrest competition accuracy, a short and stubby barrel is preferred. On the other hand, there are a lot of Palma profile barrels at 26-30" that shoot half-MOA or better.
It kinda depends on what you want to accomplish with the rifle.
December 31, 2006, 07:24 PM
optimum barrel length, relative to accuracy, for 308 and it's family of cartridges, considering benchrest shots of 400-500 yrds
December 31, 2006, 07:31 PM
At longer ranges, the benefit of shorter flight time of a higher muzzle velocity (along with using high BC bullets) as seen in less wind drift, especially in changing conditions, is probably more useful than an additional 0.05 or 0.10 MOA mechanical accuracy due to a shorter and stiffer barrel.
But the less overbore a cartridge is, the less incremental gain in velocity it will achieve for each additional inch in barrel length.
December 31, 2006, 07:47 PM
Zak so what length are you talking about??
December 31, 2006, 08:14 PM
If you intend to shoot long distance (600-1000 yards for example), a 24 to 26" barrel is a good choice for the 243, 260, 7-08, and 308. A quality barrel of that length chambered by someone who knows what he is doing should not have a problem producing 1/4 - 1/3 MOA mechanical accuracy at 100 yards if you can shoot that well.
By increasing to the 27-30", you gain advantage due to less wind drift (and to a lesser extent less drop). For a .260 Remington shooting a 139gr Scenar at 2800-2925fps, each additional 25 fps in muzzle velocity reduces the wind drift approximately 1" per 10mph cross. Like I said, it's a marginal gain.
In 308, most people recommend against barrels shorter than 22" if they intend the rifle to reach to 1000 yards due to many loads going trans-sonic before reaching the target.
December 31, 2006, 08:22 PM
I think an 18" barrel is a great compromise in length/velocity/manueverability/weight, etc...
December 31, 2006, 08:38 PM
The definitive article about barrel length and accuracy:
Long, but definitely worthwhile.
December 31, 2006, 08:38 PM
For a 308 I think a 20 inch is prime because it normally allows all powder to be burnt. A standard GI loading will burn off in around 18 inches of barrel, and allowing for a bit of that length to be taken up by the chamber gives 20 inches to be "about right".
Remember that powder doesn't burn just in the brass, but also in the barrel, so barrel diameter and length gives you the total "burn volume".
That means that the 338 Federal and 358 Win could have the same "burn volume" in a shorter barrel than the 308 because the bore diameter is larger.
Conversely the 7mm-08, 260 Rem, and 243 Win would need a longer barrel to have the same "burn volume" as the 308.
Unfortunately I don't have the drive to figure out the exact "burn volume" for each cartrige listed. But using some EXTREMELY SIMPLE LINEAR thinking and math, 358 Win = 18 inch bbl, 338 Fed = 19, 308 = 20, 7mm-08 = 21, 260 Rem = 22, 243 Win = 23 inch bbl.
Just remember that EVERY barrel length and contour is a compromise. Match rifles and tactical rifles get superior accuracy by sacrificing weight and handiness for rigidity. Pick what feels right for you, and is designed for your purpose.
December 31, 2006, 08:40 PM
if they recommend barrels not shorter than 22" for 1000 yds shots, for 400-500 yds a 22" will be excellent, but with a shorter barrel could this calibers (308, 7mm-08, 260, 243) be as accurate in benchrest shots from 400-500 yds.
December 31, 2006, 08:42 PM
Good points all.
I also point out that you don't see many 21.75" long barrels in F-class.
Also note that 100-yard benchrest shooting, indoors with absolutely no variance in atmospheric conditions (ie, no wind) totally eliminates one of the biggest obstacles to accurate long-range shooting: wind and the environment.
December 31, 2006, 09:02 PM
Houston warehouse, great story, I have the answer
January 1, 2007, 12:09 AM
Bear in mind that the Houston warehouse was an indoor 100 yard range.
Things change at 500 yards. Like Zak says, a standard target-varmint barrel length of about 26 inches would be hard to beat. The short but stiff theory kind of runs out of gas about 200 or at most 300 yards.
18 inches is for .22 lr.
January 1, 2007, 12:20 AM
I have a 308 with a shilen match 24 inch barrel, I ask the question to figure out if with a shorter barrel lenght the acuracy won't change, I know that speed will, but I still don't know how acurate it could be, I want to build a 260 Rem in a Mauser action that I have resting since 4 years ago and I want to fit it with a target barrel, that's all about.
January 1, 2007, 03:09 PM
My own chronograph results indicate the ~22" is optimal for most .308 loads. Less showed a fairly dramatic decrease in velocity, while more showed a very negligeable increase. The results varied, depending on powder and bullet, but 22" seemed to be the best over-all.
The barrel lengths tested on were 16", 18.5", 22" and 24". Bullets ranged from 110 to 180 grain with multiple powder types. Results for the two shorter barrels may have been slightly affected by the platforms being autoloaders, but I feel the numbers still supported the conclusion.
January 1, 2007, 03:33 PM
I agree the 22" bbl is optimal.
IIRC the standard M14 barrel was close to that length.
January 1, 2007, 04:35 PM
There is no one barrel length that is going to cover every cartridge of every caliber for every event. My .261x 47 Dietz has a full bull 16" barrel. Shoots in a hole at 100 yards. My Rem 40x in 30/338 mag has a 30" barrel and shoots in a hole at 100 yards. My 6.5x 06 Apex has a 23.5" barrel and shoots in a hole. All of these barrel lengths are adjusted to the cartridge capacity and getting maximum benefit from the pressure curve. Note: speed means nothing in shooting paper if you can't keep it in the x ring. Look at it from another view. The 6mm Remington has the prime case capacity for the 6mm bore. Most of these rifles will have a 22-24" barrel. Now compare that to a 6x 284 cartridge. Much more powder to burn and is an obviously overbore cartridge. You can either go longer on the barrel and use the slower burning powders that can take advantage of the case capacity or use a faster burning powder which negates the use of such a large case for the diameter of the bore. Either way, the pressure curve rules the length of the barrel if you want the best accuaracy and efficiency from a cartridge.
I'm sure your mileage will vary
January 1, 2007, 05:10 PM
Optimum for WHAT?
Are you arming a battalion, shooting 100-200 yd benchrest, or going for some range?
I shoot a little Long Range in F-class, usually alongside the Conventional shooters; and barring the Service Rifles limited by rule to 20" AR or 22" M14/M1A, my 26" Savage .308 and some 24" Remington factory guns are the shortest barrels there. Optimization doesn't figure in at 600-1000 yards, the Law of Diminishing Returns is ignored; shooters want the Most, even if it is not a whole lot more than "optimum." The barrels and bullets are of good quality and mechanical accuracy is adequate to the job if not for a benchrest shooter in the teens at 100. We are interested in whether a little unnoticed shift in the breeze will blow us out to the 9 ring or merely a wide ten.
January 1, 2007, 08:08 PM
Optimal for various uses.
Not too short to give up too much velocity.
Not too long as to be unhandy when carried.
The original "question" was about optimal length for a varity of rounds, with no specified use stated other than later with reference to accuracy.
Not every rifle will be shot exclusively off of a bench and/or in a match.
Someone may for example live in an area that has a mix of both open and close in terrain that would make a 22"bbl rifle with a around a #5 contour barrel pretty handy if he is skilled enough to employ it.
For several years I had a very similar rifle built on a '98 action in a McMillian HBR stock. It was very stabile in shooting in any position and made some precise off hand shots possible. It was also pretty easy to move with it through the brush despite it's weight.
These days I've "diversified" though and have .308's with barrel lengths from 17"-26".
January 2, 2007, 01:20 AM
Barrel length has no effect. Barrel profile (contour) does. Crowning does. The quality of the bore and rifling does, as does the precision of the fit with the action.
length alone has no effect on the accuracy of a barrel. Length + diameter (contour) has an effect on the harmonics, as well as how the barrel heats and cools. There is no "most accurate length", without considering all the other factors. Generally speaking, a quality barrel that is thick for it's length will be more accurate for shot strings. Skinny "whippy" barrels can also be quite accurate, but usually not for long strings.
A lot depends on what you want it to do. And for how long at a time. Many hunting rifles with slender barrels are very accurate for 2-3 shots, but open groups up as they heat up. Heavy barrels usually don't, or if they do, not as much.
There is no "correct" answer for your question, only generalities. I hope this helps.
January 2, 2007, 03:44 AM
I thought the topic was about accurate hunting rifles, not target rifles, since generally the calibers in question are used primarily for hunting, bar the 308 for F-class. I just doen't see the 358 Win as a benchrest caliber, though every other bore listed has a good selection of match bullets available.
January 12, 2007, 09:55 PM
thanks, I will build a 6mm Rem Imp in the Mauser action a have and will go with a 24 inch target barrel
January 12, 2007, 10:44 PM
I'm not gonna go back and re-read, but IIRC, the Houston warehouse was 300 yards, and numerous cartridges were tested. And, the finding was that barrel length does affect accuracy.
For a hunting rifle, of course, ultimate accuracy is less important, when considering other factors such as velocity. For example, I'd definitely stay with the 26" barrel on my '06, just because I can get above 3,000 ft/sec with that length; I wouldn't be able to with 21.5". And, 3/4 MOA is quite adequate for any big game animal out to some 400 or 500 yards.
January 13, 2007, 04:34 AM
I just happen to like carbines, so, for me, a 18-20" barrel is just about right. Easy to carry, good for hunting, and accurate enough.
I've never shot anything with a 30" barrel, but for anything other than benchrest shooting, that would strike me as awkward.
January 13, 2007, 08:50 AM
I had my win mod 70 30-06 cut to 18.5, crowned, ported, trigger adjusted stock shortened 2" and 1" rubber added. Shortened cause i hunt from enclosed stand and short barrel easier to move window to window. Older gunsmith(80+) who did work said to shoot 130 gr or lower cause all powder would not burn. I roll deer with 125 gr @ 60-110 yds. Most that did not drop went bout 20 yds. Feels like shooting a 22 mag. Love it.
January 14, 2007, 05:21 PM
I do not care about target rifles. I am never going to win a benchrest match. Plus, the differance between .5 MOA @ 100 yds. vs 4.0 MOA is totally meaningless unless the target is paper. A live animal assumes ambient temperature whether his vital organs are penetrated within 1/2 inch or 2 inches at 100 yards. I personally cannot imagine a scenerio where I would take a shot at any range over 250 meters. I think this accuracy thing is WAY over blown.
January 14, 2007, 05:36 PM
The original poster is interested in accuracy to 400-500 yards, and accuracy does matter.
January 14, 2007, 10:25 PM
It's logical that a shorter or stiffer barrel would be more accurate.A longer barrel would gain more velocity.And ,I have no problem picking 21 3/4 as a good length.But,to say it is harmonically superior seems to be a stretch.Thickness of the barrel,type and quality of barrel steel,bullet weight,bullet velocity,caliber,even fast versus slow powder are going to have their effect on harmonics.The best lengths for a hunting rifle are the standard lengths usually offered by the manufacturers.Generally 22 inch for a 308 case based caliber,24 inch for 30-06 based and 26 inch for some magnums. It's a consensus of opinion gathered over several decades.
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