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The Range
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S&W J-Frame Airweight Models Life Expectancy
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<blockquote data-quote="jhb33rd" data-source="post: 3816061" data-attributes="member: 48450"><p>Well here is something to chew on. The 38 is anywhere from 700fps to the +p 1200 fps (High End) muzzle velocity. This article is for a rifle with a 24" barrel. You do the Math cause I ain't smart enough...... </p><p></p><p><strong>Startling Facts About Barrel Life</strong></p><p><strong></strong></p><p><strong>Barrels Lose Accuracy After a Few Seconds of Bullet-in-Barrel Time</strong></p><p></p><p>Here’s a little-known fact that may startle most readers, even experienced gunsmiths: your barrel wears out in a matter of seconds. The useful life of a typical match barrel, in terms of actual bullet-in-barrel time, is only a few seconds. How can that be, you ask? Well, you need to look at the actual time that bullets spend traveling through the bore during the barrel’s useful life. (Hint: it’s not very long).</p><p></p><p><strong>Bullet-Time-in-Barrel Calculations</strong></p><p>If a bullet flies at 3000 fps, it will pass through a 24″ (two-foot) barrel in 1/1500th of a second. If you have a useful barrel life of 3000 rounds, that will translate to just two seconds of actual bullet-in-barrel operating time.</p><p></p><p>Ah, but it’s not that simple. Your bullet starts at zero velocity and then accelerates as it passes through the bore, so the projectile’s average velocity is not the same as the 3000-fps muzzle velocity. So how long does a centerfire bullet (with 3000 fps MV) typically stay in the bore? The answer is about .002 seconds. This number was calculated by Varmint Al, who is a really smart engineer dude who worked at the <a href="http://www.llnl.gov/" target="_blank">Lawrence Livermore Laboratory</a>, a government think tank that develops neutron bombs, fusion reactors and other simple stuff.</p><p></p><p>On his <a href="http://varmintal.com/atune.htm" target="_blank">Barrel Tuner page</a>, Varmint Al figured out that the amount of time a bullet spends in a barrel during firing is under .002 seconds. Al writes: “The approximate time that it takes a 3300-fps muzzle velocity bullet to exit the barrel, assuming a constant acceleration, is 0.0011 seconds. Actual exit times would be longer since the bullet is <em>not under constant acceleration</em>.”</p><p></p><p>We’ll use the .002 number for our calculations here, knowing that the exact number depends on barrel length and muzzle velocity. But .002 is a good average that errs, if anything, on the side of more barrel operating life rather than less.</p><p></p><p><strong>Gone in Six Seconds. Want to Cry Now?</strong></p><p>Six seconds. That’s how long your barrel actually functions (in terms of bullet-in-barrel shot time) before it “goes south.” Yes, we know some barrels last longer than 3000 rounds. On the other hand, plenty of .243 Win and 6.5-284 barrels lose accuracy in 1500 rounds or less. If your barrel loses accuracy at the 1500-round mark, then it only worked for three seconds! Of course, if you are shooting a “long-lived” .308 Win that goes 5000 rounds before losing accuracy, then you get a whopping TEN seconds of barrel life. Anyway you look at it, a rifle barrel has very little longevity, when you consider actual firing time.</p><p></p><p>People already lament the high cost of replacing barrels. Now that you know how short-lived barrels really are, you can complain even louder.</p></blockquote><p></p>
[QUOTE="jhb33rd, post: 3816061, member: 48450"] Well here is something to chew on. The 38 is anywhere from 700fps to the +p 1200 fps (High End) muzzle velocity. This article is for a rifle with a 24" barrel. You do the Math cause I ain't smart enough...... [B]Startling Facts About Barrel Life Barrels Lose Accuracy After a Few Seconds of Bullet-in-Barrel Time[/B] Here’s a little-known fact that may startle most readers, even experienced gunsmiths: your barrel wears out in a matter of seconds. The useful life of a typical match barrel, in terms of actual bullet-in-barrel time, is only a few seconds. How can that be, you ask? Well, you need to look at the actual time that bullets spend traveling through the bore during the barrel’s useful life. (Hint: it’s not very long). [B]Bullet-Time-in-Barrel Calculations[/B] If a bullet flies at 3000 fps, it will pass through a 24″ (two-foot) barrel in 1/1500th of a second. If you have a useful barrel life of 3000 rounds, that will translate to just two seconds of actual bullet-in-barrel operating time. Ah, but it’s not that simple. Your bullet starts at zero velocity and then accelerates as it passes through the bore, so the projectile’s average velocity is not the same as the 3000-fps muzzle velocity. So how long does a centerfire bullet (with 3000 fps MV) typically stay in the bore? The answer is about .002 seconds. This number was calculated by Varmint Al, who is a really smart engineer dude who worked at the [URL='http://www.llnl.gov/']Lawrence Livermore Laboratory[/URL], a government think tank that develops neutron bombs, fusion reactors and other simple stuff. On his [URL='http://varmintal.com/atune.htm']Barrel Tuner page[/URL], Varmint Al figured out that the amount of time a bullet spends in a barrel during firing is under .002 seconds. Al writes: “The approximate time that it takes a 3300-fps muzzle velocity bullet to exit the barrel, assuming a constant acceleration, is 0.0011 seconds. Actual exit times would be longer since the bullet is [I]not under constant acceleration[/I].” We’ll use the .002 number for our calculations here, knowing that the exact number depends on barrel length and muzzle velocity. But .002 is a good average that errs, if anything, on the side of more barrel operating life rather than less. [B]Gone in Six Seconds. Want to Cry Now?[/B] Six seconds. That’s how long your barrel actually functions (in terms of bullet-in-barrel shot time) before it “goes south.” Yes, we know some barrels last longer than 3000 rounds. On the other hand, plenty of .243 Win and 6.5-284 barrels lose accuracy in 1500 rounds or less. If your barrel loses accuracy at the 1500-round mark, then it only worked for three seconds! Of course, if you are shooting a “long-lived” .308 Win that goes 5000 rounds before losing accuracy, then you get a whopping TEN seconds of barrel life. Anyway you look at it, a rifle barrel has very little longevity, when you consider actual firing time. People already lament the high cost of replacing barrels. Now that you know how short-lived barrels really are, you can complain even louder. [/QUOTE]
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