Barrel Length vs. Effects on Projectiles.
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308 Winchester / 7.62x51mm NATO: Barrel Length versus Velocity (28″ to 16.5″)
308 Winchester / 7.62x51mm NATO: Barrel Length versus Velocity (28″ to 16.5″) Introduction Released by Winchester in 1952 (and adopted by NATO in 1954 as the 7.62x51mm NATO), the 308 Wi…
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- Mar 15, 2018
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The Truth About Barrel Length, Muzzle Velocity and Accuracy - The Truth About Guns
◀Previous Post Next Post▶ Josh Wayner’s taken it upon himself to challenge what everyone “knows” as far as barrel length, velocity and accuracy are concerned. According to his results, the conventional wisdom ain’t all that wise when it comes to longer-barreled ballistics. The only question...
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The length of a barrel actually have more profound effects on bullets than many would think. The effects are mostly due to temperature difference along the barrel and reverberations from the previous shot.
In National Muzzleloading Rifle Association long range shoots using rifled muskets and cartridge long arms of the CW-Indian Wars era, it is well known that serious sharpshooters who cared about winning gold would opt for much shorter two band guns and 'musketoons' than regular 3-band infantry rifles. Upon each shot fired, a significant amount of heat and infrasonic vibration gets thrown down the tube. That heat dissipates from the metal at varying speeds depending on each section. Exposed sections of barrel cool down much faster than sections surrounded by stock or receiver. Due to different sections of the barrel ending up with different ambient temps, microscopic bends and twists too minor to detect without instruments occur in the tube and the next shot that is fired down that bore will never have the same pattern and flight path as the previous bullet. If you only have a long barreled gun available for precision use, glass-bedding the stock and barrel gap can help in reducing the fluctuation of performance accrued by each shot. There is a reason why towards the end of the Civil War, officially designated 'sharpshooters' units on both sides opted for shorter versions of standard infantry issue long arms or had new guns made altogether.
In National Muzzleloading Rifle Association long range shoots using rifled muskets and cartridge long arms of the CW-Indian Wars era, it is well known that serious sharpshooters who cared about winning gold would opt for much shorter two band guns and 'musketoons' than regular 3-band infantry rifles. Upon each shot fired, a significant amount of heat and infrasonic vibration gets thrown down the tube. That heat dissipates from the metal at varying speeds depending on each section. Exposed sections of barrel cool down much faster than sections surrounded by stock or receiver. Due to different sections of the barrel ending up with different ambient temps, microscopic bends and twists too minor to detect without instruments occur in the tube and the next shot that is fired down that bore will never have the same pattern and flight path as the previous bullet. If you only have a long barreled gun available for precision use, glass-bedding the stock and barrel gap can help in reducing the fluctuation of performance accrued by each shot. There is a reason why towards the end of the Civil War, officially designated 'sharpshooters' units on both sides opted for shorter versions of standard infantry issue long arms or had new guns made altogether.
I have done a lot of load development in the 308 with different barrel lengths. As far as mag length ammo goes, I found that with 175gr bullets, 24” beats 26” for accuracy, node size, ES/SD, and velocity is basically the same. I think that barrel length as a variable, does influence a load more than just in the velocity department.
If you reload I don’t feel there’s much difference except speed.
I’ve definitely seen a benefit to a 20” or 24” for factory ammunition.
Short range BR run short stumpy barrels and I’m sure it’s for the benefit of the harmonics but I want the speed and don’t need .0XX groups.
I shoot primarily MOA sized target out to a mile, I like the extra speed to maintain supersonic as long as possible and the wind Benefits.
This is a rabbit hole I’m not really interested in as I feel there far more important fish to fry to be a better shooter.
I’ve definitely seen a benefit to a 20” or 24” for factory ammunition.
Short range BR run short stumpy barrels and I’m sure it’s for the benefit of the harmonics but I want the speed and don’t need .0XX groups.
I shoot primarily MOA sized target out to a mile, I like the extra speed to maintain supersonic as long as possible and the wind Benefits.
This is a rabbit hole I’m not really interested in as I feel there far more important fish to fry to be a better shooter.
I've seen/done a couple of by-the-inch tests with a couple types of factory ammo tested at each length for 10 shots each. No trends in accuracy either way, no trends in ES/SD either way, but 20-30fps per inch mv loss depending on caliber.
Also noticed no accuracy difference between a machined 11* crown and a chamfer/deburr tool.
Also noticed no accuracy difference between a machined 11* crown and a chamfer/deburr tool.
I have 26” .308 barrels down to 20”.
Speed is the only difference practically speaking. I don’t chrono anything so who knows with the es/sd bullcrap. I make the same hits with all. The shorter tubes need a few more tenths of elevation. Do not over complicate.
You aren’t trying to make excuses for your misses are you.?
Speed is the only difference practically speaking. I don’t chrono anything so who knows with the es/sd bullcrap. I make the same hits with all. The shorter tubes need a few more tenths of elevation. Do not over complicate.
You aren’t trying to make excuses for your misses are you.?
No. I have heard before that a 20" barrel is all that is needed to obtain the full potential of a .308. Before believing I want the facts. Plus lugging around a 28" varmint barrel is not as fun as it used to be.
20" is not all that is needed as you can get more velocity from a longer barrel but a 20" works really well for an all around rifle and if you wanted to keep it short.
it prolly depends on how far out you really want to go.
i have heard the opposite, that 20" isn't enough to hit out to 1000 yds or beyond (at sea level) *consistently.
this was from somebody that claimed to compete regularly in california (at near sea level).
the claim was that the extra velocity from a longer barrels made a difference @ 900 yards and out (at sea level).
self proclaimed expert says 20" rifles are out of the the competitions at 900 most of the time.
*expert defined "effective or consistent" as being able to walk out on any day, under any conditions, calculate dope and get a first shot hit.
"if you have to take a few shots to hit it, it isn't effective at that range..."
here on SH however, many shooters say 1000 is within the effective range of a 20" .308, and they do it all the time.
i have only taken my 20" .308 out to just over 600 yards (max at the range), so i am not able to say from experience either way.
Do you know of any credible tests out to 1000 with a 20" barrel.
Primary range for the rifle is probably max 800 but not counting out occasional 1000 yard shots. It's kind of one of those things I want to be prepared for just in case.
most of my focus has been on my own rifle (Scar 20S) which is somewhat handicapped with a 1:12 twist.
even FN itself now claims it is "capable of sub-minute of angle accuracy out to and beyond 1,000 yards."
of course they must have some basis for these claims, but i have not discovered detailed reports of any kind.
while i have also seen 800m as the realistic effective range, another hide member (that competes) says he is good out to 1000, but can't shoot tight groups due to the limitations of using 175gr SMK.
your rifle may be completely different.
a 1:11.25 twist would allow you to get spin stable with heavier bullets, which might extend your range.
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I’ve hit steel a few times out 1300 to with my buddy’s M14.
22”
DA was 800.
It did better than I thought it would.
FGMM 168&175.
8-900 was not bad but it was definitely a bit frustrating at 1300 but doable.
The longer the distance is, the more environmentals such as wind come into play, which more velocity will help to negate.
If I was shooting 1000 yard F-class or benchrest, I would take a longer barrel for more velocity to improve ballistics and mitigate the environmentals as much as possible.
However, I don't play those games, and my 21.75" bbl TacOps rifle in .308 shoots more then fine and predictably to 1,200 yards (furthest I've shot it). A lot of that shooting was done close to sea level.
A 24"+ barrel is no more accurate then a 20" barrel. In fact, if you believe the Houston Warehouse lore, they found 21.75" barrels to be the most accurate. How true that is I don't know. The differentiator for barrel lengths is velocity, the more of which you have helps mitigate any change in environmentals. So it's not so much a matter of pure accuracy/precision, but one of mitigating elements out of your control.
If I was shooting 1000 yard F-class or benchrest, I would take a longer barrel for more velocity to improve ballistics and mitigate the environmentals as much as possible.
However, I don't play those games, and my 21.75" bbl TacOps rifle in .308 shoots more then fine and predictably to 1,200 yards (furthest I've shot it). A lot of that shooting was done close to sea level.
A 24"+ barrel is no more accurate then a 20" barrel. In fact, if you believe the Houston Warehouse lore, they found 21.75" barrels to be the most accurate. How true that is I don't know. The differentiator for barrel lengths is velocity, the more of which you have helps mitigate any change in environmentals. So it's not so much a matter of pure accuracy/precision, but one of mitigating elements out of your control.
My apologies, should have been more specific. This is 6.5 Creedmoor with factory Hornady ammo.
nice, thanks!
so you're saying there's a chance...lol
i can spin 175gr SMKs, even with 20" 1:12, so i'll have to see for myself. velocities might not be that different.
i plan to try the higher velocity superformance match, even though not SMKs, if i can't get there with FGMM.
Give it a go and find out for yourself, it's really the only way to find out.
Thankfully this kind of learning is really fun, so enjoy. Your setup is probably more capable then you realize.
Anyone who says a 20" .308 can't hit consistently at 1000 is someone I wouldn't listen to and is no "expert". Probably old 168 SMK thinker with mention of 900 yard max. With today's .308 bullets it is quite easy to do.
And better tell all the F Class shooters to turn in their 28-30" barrels for those more accurate 21.75" barrels. Man you got to love the internet. LOL
And better tell all the F Class shooters to turn in their 28-30" barrels for those more accurate 21.75" barrels. Man you got to love the internet. LOL
Secrets of the Houston Warehouse
www.angelfire.com
I wouldn't read into it too much. For short range applications, which the above is essentially all about, perhaps a shorter barrel may be more accurate then a longer one due to barrel harmonics. In reality, most shooters wouldn't be able to shoot the difference, assuming there is one.
My best 100 yard 5 round group is from a 28" barrel (picture below). If that barrel was 21.75" would the group below be smaller? I really don't think so.
Figure out what applications you want to use the rifle for, and from there decide what the optimal barrel length is. I wouldn't get too hung up on the Houston Warehouse 21.75" thing. That's UBR benchrest with pretty much zero environmentals, and it's really all hearsay. There's no evidence that I'm aware of to corroborate it. My point is that there is no practical difference in accuracy between short and long barrel, just velocity and down range ballistics to help counter environmentals.
My point with that comment wasn't that 21.75" barrels are the most accurate, I don't necessarily believe that either. My point is that from a pure accuracy and precision standpoint, you won't see a practical difference in barrel lengths.
What does matter is the velocities you may achieve, hence my posts above about why F-class shooters and 1000 yard BR guys use longer barrels - to attain the best ballistics to best mitigate the elements out of your control.
People shouldn't read into the 21.75" barrel length comment too much. My point being, if you're a casual shooter you can be really effective and have fun at long distances with short barrels. If you are shooting in a discipline where every point counts and you need the biggest competitive advantage, go with a barrel length that will provide the best down range ballistics to mitigate elements out of your control.
19in .308 Krieger shooting 1k yards at Quantico.
Did I hit everytime? Hell no
Did the guys shooting 6.5cm with 20+ barrels smoke check me with wind/elevation adjustments? Hell yes.
Do I learn something new each time I shoot the shorter barrel at longer distance? Fuck yes.
Did I hit everytime? Hell no
Did the guys shooting 6.5cm with 20+ barrels smoke check me with wind/elevation adjustments? Hell yes.
Do I learn something new each time I shoot the shorter barrel at longer distance? Fuck yes.
This.
I really enjoy lobbing shots out there and seeing what happens.
Sometimes your kinda disappointment and sometimes your pleasantly surprised.
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i am mapping fire zones for the zombie invasion, ranging landmarks ahead of time, so i don't have to do that when they are flooding over the bridges and walls.
knowing my actual realistic effective range will help me choose firing positions that can cover critical points of defense.
