You’ve probably heard “Barrel length doesn’t affect accuracy!” at some point when discussing firearms. Like all good urban legends, this one has a kernel of truth, at short ranges a few inches more or less than a “standard” barrel isn’t going to make much difference.
But the myth doesn’t stand up to much scrutiny beyond that. A 20″ AR-10 pushing a Berger 185gr bullet scored a perfect 200 at 1000 yards in the hands of a USAMU shooter, and the M16A2NM USAMU custom shop rifle can clean the target at 1000 yards using handloaded ammunition as well. Logic would say that if you can reach 1k you should be able to reach 1.5k right? I mean if the sights could adjust that much (and yes, I do know people who shoot 308 Win out past a mile, but at that point they have to use hold UNDERs to make shots under 300 yards because they’ve canted the scope so much).
Does this mean that every 20″ 223 or 308 out there can clean the target at 1000 yards? No, clearly not, some have an improper twist rate to stabilize bullets, some have a crappy chamber that makes it hard to seat bullets long enough to get a good consistent jump to the lands. And more to the point, putting a USAMU tuned weapon into the hands of the average shooter isn’t going to do the average shooter much good (it certainly won’t hurt though) without someone world class making wind calls.
But when it comes to long range accuracy and barrel length, I really want to focus on one thing which is “environmental dispersion.” To state things as clearly as possible, group sizes change as distance increases.
Bart Bobbitt has gone on record stating that he expects 1/10th MOA increase in group size per 100 yards. If anyone has a copy of the book “The M1 Garand: Handling, Shooting, and accurizing the first gas operated U.S. Service rifle”http://www.amazon.com/The-M1-Rifle-Handling-accurizing/dp/B004LCT7PW you now know whose profile graces the cover.
So why do groups grow with distance? Air currents and ammo inconsistency. Air is not a static fluid, it is always heating and cooling, blowing this way or that. This is why Sierra can get such amazing groups in their test tunnels, or the famous (or infamous) “Houston Warehouse” http://bulletin.accurateshooter.com/2012/10/secrets-of-the-houston-warehouse-read-this-classic-article/ because when you eliminate air currents as an environmental variable you eliminate the largest source of group dispersion.
So how does barrel length interact with air currents? Two things come to mind, velocity and consistency.
First up is velocity. Every standardized cartridge was developed with a given performance in mind. The higher the velocity the less time a bullet has to interact with the atmosphere. If you are shooting long range you want as much velocity with the highest BC bullet you can get as long as that bullet an handle the transition to subsonic consistently.
Second up is consistency. A short barrel that doesn’t ensure 100% powder burn will be less consistent than a longer barrel that gets 100% burn with the same load. Even Federal Gold Medal Match is no exception, 11fps Standard Deviation with a 16″ barrel, and 9 fps SD with a 20″ barrel (notes I’ve taken from others who’ve chrono’d their FGMM loads and published data). This doesn’t mean that you can’t handload specifically for a 16″ barrel to get 100% burn, it just means that even if you get your SD equal to the longer barrel, you still won’t have the velocity of the longer barrel.
So are longer barrels more accurate? Not necessarily, you get different harmonics with different barrel lengths, and while the old wisdom is that “stiffer is better” has truth to it, the real answer is that “consistency is better” so even stiff barrels can shoot like crap when fed inconsistent ammo. Longer barrels make it easier to get consistent internal ballistics which makes it easier to get better long range accuracy.
So what affects accuracy? everything. Within reason barrel length doesn’t matter much, but the longer the range you are shooting the more it matters. I’ve said it before and I’ll probably say it again, every firearm is just a set of compromises. The problem is that calculating how much barrel length affects accuracy is problematic because it is all set on environmental dispersion if all else is equal (and all else is never equal).
But to illustrate, a 175gr SMK at 2700 fps with a 1mph cross wind is 104 inches off target at 1k yards. The same bullet at 2550 fps is 115 inches off, or 0.9 MOA extra dispersal per every mile per hour of wind. This is why many snipers really like the 300 Win Mag and various 338 Magnums for sniper missions, the better ballistics makes operator errors in estimation less of a problem at long distances in unknown conditions.
The difference between an M16 and an M4 at 200 meters is irrelevant. At 900 meters it is much more relevant. When you get to the edges of performance, barrel length affects accuracy.
http://randomthoughtsandguns.blogspot.com/2015/07/ballistic-myth-barrel-length-doesnt.html
Thanks again Paraclete
love my 300 Win Mag .. reach out and touch your target
the only draw back i found in hunting with mine , any close range hit goes( can Go) right thru the animal , and that doesn’t always produce a clean kill if it doesnt hit a vital , don’t get me wrong i sure wouldn’t like a Win Mag 300 projectile to rip thru my fleshy parts , just bear in mind they are long distance “game” rifles for a reason
Have you tried ballistic tips?
No I havent yet, most of the rounds I put down range or at a food target were FMJ’s or a lead tipped ( if they can be considered a ballistic tipped or not im not sure )
but with as much balls behind a 300 round at 50 to 60 yards , its going thru most any meat and bones target at that close a range , I shot a good size deer with my A-Bolt at about 60 yards and it zinged right thru him like he was paper , hardy phased the animal , sure in due time he would bleed out , im just too lazy to chase after dinner so i nailed him in the head with the next shot .. didnt care to mount his head anyways …lol
even with a ballistic tip at that velocity at a close up target , if you dont hit something relatively solid or hard inside that target (animal) its got a pretty good chance of going right thru
I’ll buy a box of those ballistic tipped and make up a few rounds to try next season though .. but rarely do i get such a close shot
I hunt with130 grain ballistic tipped .270
Great flat line and a fantastic bone crusher
Typically, Georgia Arms’ loads ….
but they’re too proud of their product
now-a-days …nearly 40.00 per twenty…..
But I’ve got ’em beat ….in the day, I always
made it a point to get a box or two at each
gun show, whether I needed it or not.
Since I bought way more than I shot, there’s a great reserve set aside for the “two legged moose”
What this article really shows is that barrel length affects range, not accuracy.
Long distance requires a barrel that will get the bullet to the target, and for that a longer barrel is better since you will get more speed and distance (more powder burn in the barrel increasing velocity) out of the round.
Accuracy still depends on all the things that make a round accurate at short distance (100 to 300) as well – a good barrel (stable at all temperatures, from first “cold” shot to the last “hot” one; hence “stiff”) with proper twist rate for the round, a good crown on the barrel, and a good chamber, and consistent ammo (that’s why match ammo is marked per batch; and why it’s better to roll your own).
The atmosphere has nothing to do with the accuracy of the rifle, but the faster the bullet, the less time the atmosphere has to act on the bullet on its journey down range. It’s not up to the rifle to determine the wind, humidity and temperature, but the shooter, no matter what the length of the barrel.
Good points
have a question you may be able to answer for me
you mention the crown on the barrel end ,, If i were to install a muzzle brake on my Win Mag 300 , would that alter its long range ability ?Pro or Con?.. ie good or bad?
I would like to tame this beast a little , im not as young as i used to be and my right shoulder has had 37 years of big bore punishment , sure would like to benefit from the muzzle brakes abilities , i also want it for the ability to get back on point quicker
whats your 2 cents on this ? anyone ..
Don Boettcher would be the one to ask these questions. He shoots .50 cal and I know the muzzle break is necessary for those monsters.
You can get his number from his ad on the left hand side of this page, Don Boettcher’s Night Vision.
Personally, I believe the muzzle break will help
with your accuracy, for the simple reason that your
recoil will be under better control.
Hence, your follow through will be maintained.
And second shot recovery will be enhanced as well.
If you’re shooting semi auto.
Roger that , quicker back on point too
Both semi and Bolt , the bolt is the one i want the Brake for .. the semi uses some of the umph to bring the next player into battery so its not as bad
Every cartridge was developed around a standardised barrel length. 5.56 a 20″ .300blkout 9″ etc. Shorter barrel means more noise,flash and recoil. Longer lessens them.
Id agree the twist rate and ammo temp along with barrels thickness make bigger differences in accuracy(cold bore or auto-hot) than length. Like all things there is a point of diminishing return.
Iv never heard of a muzzle devise affecting accuracy. So long as the crown is perfect. The bullet should break contact with the barrel 360° simultaneously. Any chip or bur sends the round with a ‘tip’ or lean to it. Like over stabilizing, this causes keyholing and what ever its called when a bullet strikes canted.
Oh and 55gr fmj 5.56 eats class3 armor with a 20″ but not a 16″ barrel. 3000+fps compared to 2700 or 2800fps
Food for thought.