Ready to have a myth busted? Here's an excellent test for the accuracy of SBRs

Ready to have a myth busted? Here's an excellent test for the accuracy of SBRs

This is a discussion on Ready to have a myth busted? Here's an excellent test for the accuracy of SBRs within the Defensive Rifles & Shotgun Discussion forums, part of the Related Topics category; An excerpt from the article just so you'll have an idea what to look for and expect: "This test obliterated what was previously thought to ...

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Thread: Ready to have a myth busted? Here's an excellent test for the accuracy of SBRs

  1. #1
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    Ready to have a myth busted? Here's an excellent test for the accuracy of SBRs

    An excerpt from the article just so you'll have an idea what to look for and expect:

    "This test obliterated what was previously thought to be fact. Not only was it determined that short barreled rifles are easily as accurate a those with long barrels..."

    http://www.thetruthaboutguns.com/201...-and-accuracy/

    Bear in mind, the SBR they are referring to is 13.5". Overall, that is the average of accuracy of all the various loads, the 13.5 was more accurate than the 26" barrel. In fact, of the 26", 18", 16", and 13.5" barrel lengths tested, the 26" was the least accurate.

    This is just for the .308. I don't think we can generalize this to all calibers.
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    Interesting read. Thanks Tangle! We can talk (and talk, and talk...) about rifle/carbine/SBR accuracy at reasonable distances, yet it's seldom the gun, it's the shooter. Most , if not ALL, of my guns are more capable than I am.
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    Interesting indeed, but it kinda makes sense when talking about .308
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    It's my understanding that as long as there is sufficient barrel to stabilize the spin then a shorter barrel is more accurate.

    All things being equal and assuming enough powder burn and stabilization a shorter barrel is stiffer and has less harmonic variation. Also, because there is simply less material, a shorter barrel has a better chance of having fewer flaws.
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    Accuracy and terminal ballistics are two different things. A shorter barrel is usually more accurate because it is stiffer than a barrel of the same diameter but longer length. You need length, though, to get velocity. Without velocity, your .308 becomes far less capable due to lack of bullet performance and penetration. What is usually best for most shooters is the "compromise" length where velocity is still high enough to be useful but neither too long to be ungainly to handle nor has accuracy fallen to an unacceptable level. Long barrels are usually less accurate compared to short barrels of similar diameter because of harmonics. Stiffer barrels are more consistent and repeatable shot after shot.

    There is definitely a place for the SBR. I have one. I like it. But shortening a barrel is not a one size fits all answer to anything.
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    Indeed. The flip side to this coin is velocity. Shorter barrels need faster burning powder to generate the same velocity as slower burning powder in longer tubes. Faster burning powder in rifle quantities can be detrimental to barrel life... Along with tons of other factors, of course. I don't think it'd have a ton of effect on the .308, but a .243 or some such could see a difference. It's all a compromise, anyways.
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    That's true, terminal ballistics is different than accuracy. But this test was about accuracy. The military sets the effective range of the 5.56, 14.5" M4 at 500 meters. This is based on a soldier being able to hit a man sized target at 500 meters. However, at 500 meters the remaining energy is pitiful, but apparently enough to incapacitate a man for military purposes.

    Was it in this test that I linked that revealed the velocity drop of the .308 from a 24" to 20" barrel was practically zero?

    Also, there are few of use that would ever need to make a shot much over 200 yards and SBRs can certainly fulfill that requirement with energy to spare. Of course if we are in a situation where terminal performance at long range is more important than accuracy, then sure, we would want to give up accuracy for more down range velocity.
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    What do you call "pitiful" power levels? The 350 ft lbs of a .45, or the 200 ft lbs of a 38 snub? Put the 77 gr hpbt match in the 14" 223 AR barrel, with a decent load, and it's going to hit at 500 yds like the .45 hits at 10 ft. We've known for 20 years now that the AR15 is otentially just as accurate a setup as any bolt action. The 10" barreled XP100 was sub `1moa (scoped) 40 years ago.

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    Quote Originally Posted by useful View Post
    What do you call "pitiful" power levels? The 350 ft lbs of a .45, or the 200 ft lbs of a 38 snub?
    Neither. The M855 is a .22, not a .45 nor a .38. It relies on high velocity for terminal performance. The pitiful energy I referred to was specific. It was the M855, 62 gr round fired from an M4. At 500 meters has an approximate velocity of 1220 fps and a retained energy of 220 ft-lbs. That's pitiful. There are two problems, one the energy is low and the velocity is waaaay below what's required to get expansion. So basically the bullet makes a .22 cal through hole.

    Quote Originally Posted by useful View Post
    ...Put the 77 gr hpbt match in the 14" 223 AR barrel, with a decent load, and it's going to hit at 500 yds like the .45 hits at 10 ft. We've known for 20 years now that the AR15 is potentially just as accurate a setup as any bolt action. The 10" barreled XP100 was sub `1moa (scoped) 40 years ago.
    I like the heavier bullets, but unless one handloads, and I don't, it is very difficult to find 77 or 75 gr .223 ammo for hunting purposes. E.g. Hornady specifically states their BTHP is not intended for hunting.

    Plus, even with a 77 gr bullet there's a velocity problem. At 500 meters the velocity is a mere 1442 fps. We have to remember that this is a .22, not a .45. It is well established that the 5.56/.223 needs a minimum velocity to have effective terminal performance. While that minimum is debatable, it seems to be about 2500 fps. The problem is at velocities below this, the bullet doesn't expand, and BTHPs, at least what I've found, are specifically for matches, not hunting and the tips are not designed for expansion. So it's really not like a .45 at all that's designed to be effective at a lower velocity.

    I wish I could find some factory 75 gr stuff made for hunting. So far I can't find any, and if I do, it seems to be out of stock.
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    Might wanna take a look at the Barnes solid copper hunting bullets, you can go lower weight with stellar performance(copper being lighter than lead = lighter copper performs like much heavier lead projectiles) - IF your rifle "likes them" and it likely will IMHO

    Quote Originally Posted by Tangle View Post
    Neither. The M855 is a .22, not a .45 nor a .38. It relies on high velocity for terminal performance. The pitiful energy I referred to was specific. It was the M855, 62 gr round fired from an M4. At 500 meters has an approximate velocity of 1220 fps and a retained energy of 220 ft-lbs. That's pitiful. There are two problems, one the energy is low and the velocity is waaaay below what's required to get expansion. So basically the bullet makes a .22 cal through hole.



    I like the heavier bullets, but unless one handloads, and I don't, it is very difficult to find 77 or 75 gr .223 ammo for hunting purposes. E.g. Hornady specifically states their BTHP is not intended for hunting.

    Plus, even with a 77 gr bullet there's a velocity problem. At 500 meters the velocity is a mere 1442 fps. We have to remember that this is a .22, not a .45. It is well established that the 5.56/.223 needs a minimum velocity to have effective terminal performance. While that minimum is debatable, it seems to be about 2500 fps. The problem is at velocities below this, the bullet doesn't expand, and BTHPs, at least what I've found, are specifically for matches, not hunting and the tips are not designed for expansion. So it's really not like a .45 at all that's designed to be effective at a lower velocity.

    I wish I could find some factory 75 gr stuff made for hunting. So far I can't find any, and if I do, it seems to be out of stock.
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    So this test was conducted using just one barrel and one platform?

    A shorter barrel should be just as accurate as it was before it was cut down if the node was hit. This is much more an effect of vibration, which will change with barrel length.

    This is not to discredit SBRs. I absolutely see the validity of thier use in certain situations.
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    There is accuracy, velocity, and ballistics. Sometimes you want a short barrel, sometimes you want a long barrel.
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    If shorter barrels were more accurate, then the 100/200yd benchrest crowd would be using barrels shorter than 20+ inches (often 22-26"). The shorter = more rigid = more accurate is a misconception that sounds legitimate, and causes many people to regurgitate it on the forums.

    Way too much to write, and nobody wants to listen to me anyways, so I'll just shut my mouth now.

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    Quote Originally Posted by diggler1833 View Post
    So this test was conducted using just one barrel and one platform?

    A shorter barrel should be just as accurate as it was before it was cut down if the node was hit. This is much more an effect of vibration, which will change with barrel length.

    This is not to discredit SBRs. I absolutely see the validity of thier use in certain situations.
    I have seen a number of barrel profile and length tests over the years. I have yet to see a study that indicates nodal effects are significant, if even measurable.

    But if you can post a link or two to some tests that show nodal effects, I'd for sure be interested in seeing them!

    The tests I've seen show barrels cut in 1" increments from long, i.e. 24+ inches down to as little as 10 inches so it would be impossible to hit a node at every length, and the accuracy measurements don't show a nodal effect. Accuracy is essentially linear and changes very little with barrel length, often improving as the barrel gets shorter.

    But, an SBR is not a long range gun, nor is anyone claiming it should be. But the limitation is not accuracy, it's velocity and energy issues at longer ranges.
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    Quote Originally Posted by diggler1833 View Post
    If shorter barrels were more accurate, then the 100/200yd benchrest crowd would be using barrels shorter than 20+ inches (often 22-26"). The shorter = more rigid = more accurate is a misconception that sounds legitimate, and causes many people to regurgitate it on the forums.

    Way too much to write, and nobody wants to listen to me anyways, so I'll just shut my mouth now.
    Not true. Bench rest shooters need high velocity for pretty much one reason, shorter flight time. Some would say the high velocity is for flatter trajectory, which it does provide, but that's not an issue that's just a matter of adjusting the scope.

    So time of flight is the bench rest shooter's enemy. The longer the bullet is in flight, the more it is susceptible to atmospheric disturbances like wind.

    The shorter barrel accuracy isn't a misconception. The misconception is that by some magic means a bullet would know whether it was fired from a short or long barrel. To deny the short barrel accuracy is to deny stringent test results like the produced by the tests linked in the OP and such as this one:

    SWAT Article BARREL LENGTH

    I think where the longer barrel is more accurate claim comes from is when iron sights were used and the longer sight radius allowed more precise aiming. When scopes came into widespread use, we started seeing that with sight radius no longer a problem, the notion that longer barrels are somehow more accurate was dispelled.

    These quotes from an article Masod Ayoob wrote:
    Second, the optical sight came fairly late to the evolution of the firearm. Original "iron sights" atop the gun were the only index the shooter had to align the barrel with what he wanted to hit. The distance between the rear sight and the front sight, known as "sight radius," created a classic example of "simple geometry in action".

    Since the variable element of each individual's vision was involved — and also, of course, the ever-present shooter's curse of "human error" — it made sense that the longer the barrel, the better. The rear sight was at the rear of the gun, and the front sight usually just above and behind the muzzle. In other words, the longer the barrel, the longer the sight radius (the distance between the rear and the front of the "iron sights") and therefore, the less margin for unnoticed human, visual error. Hence the old rule of thumb that the longer the barrel, the more accurately the user could probably shoot.

    Once again, the "accuracy" element of the longer barrel had been rendered moot ... but there was still the matter of the greater power that a longer barrel could engender in the projectile the rifle put forth.

    Here's another test that shows shorter is more accurate:

    http://www.bellmtcs.com/store/index.php?cid=580
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