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Posted: 9/30/2005 1:53:36 PM EDT
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1) Would a 16" bull barrel be inherently less accurate than a 20" of the same make? 2) what would the effective range of a 20" BB be with say 75gr black hills or other match heavier grain ammo? |
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1) Would a 16" bull barrel be inherently less accurate than a 20" of the same make? - Nope 2) what would the effective range of a 20" BB be with say 75gr black hills or other match heavier grain ammo? -I guess it depends on if you are able to hit them in the head or, nick them in the left calf. |
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What is your definition of "effective range" - do you mean fragmentation, a certain velocity, or are you purely talking about accuracy. The accuracy from a 16" and 20" should be about the same, but the bullet drop and shorter sight radius might make the 16" a little more difficult to keep on target at extended ranges with iron sights. |
The distinction between accuracy and precision here is mistaken. Precision is the "spread" of a sample, determined statistically by measures of spread such as standard deviation. In shooters' parlance, precision is "group size". Accuracy, on the other hand, is how close to a hypothesized mean somehting comes. In shooters' parlance, it is how close your average shot is to the bulls-eye. These two terms are frequently mistaken Moreover, the correct (party line) answer to the original question is that barrel length affects neither accuracy nor precision, only velocity. |
I wish I could understand. I asked the same question under Competition shooting board at General. I saw lots of explanations but I am still not convinced... hy.gif Does barrel length affect accuracy in a smooth bore gun? I guess without rifling longer barrel would provide correct path for a longer time. Thus increasing accuracy? I just feel that there must some reason (even wrong) why so many people automatically think longer barrel means better accuracy. |
Those rounds may get blown over a bit more but they will all still impact in the same place. That is what the windage knob is for. At my last long range match(1K yds), I shot a 20" AR. I came off the line with 12 minutes of wind. The guy next to me was shooting a 26" barreled 6.5x284. He came off the line with 4 minutes. My bullets got blown out more, but I still managed to keep most all of them in the 10 ring. |
| It is still harder to be accurate when your errors in esitmation on distance and wind yeild worse results. I think the best term would be "practical accuracy" because if you got 2 guys one with a higher velocity rifle and one with lower the higher velocity rifle would be closer to the intended POA more often than the slower rifle all things being equal. |
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I would hope no one ever shoots at an "unknown distance", slapping off a shot without making an attempt to adjust for drop is damn poor form. barrel length doesn't have a thing to do with group size. velocity affects trajectory and TOF (windage comp) but if you could launch identical bullets at identical velocities from otherwise identical barrels the shorter barrel should have a smaller group. |
In the smooth-bore gun, this might be true, but it's not really relevant for most of us. I have seen results of a test in which a 24" barrel was cut down 2" at a time to 8". No change in accuracy or precision, but decreased volocity with each cut. Long range shooters generally use longer barrels to get more velocity, so that there is less deviation at long ranges. For example, using the Barnes Ballistics program, for a .223 with a ballistic coefficient of .271 at 3000 fps muzzle velocity, and general sea level atmospheric conditions, we see that at 800 yards, the drop is 30 MOA. with a velocity of 3200 fps, the drop is 25.5 MOA. So, you'll be 36 inches lower with the slower load. So what, you might say, I'll hold higher. That's true, with target knobs, you just dial higher to compensate. But suppose you measured your range at 800, and it's really 825, because your rangefinder registered on a nearby object, not the target, or some other changing condition such as wind, or temperature or elevatiion or up or down angle, that you have not accounted for. That extra 25 yards throws off the slow load by 2.06 MOA, which is 16.5 inches at 800 yards. It throws off the faster load by 1.78 MOA which is 14.2 inches at 800 yards. The greater the distance and the greeater the veolocity, the greater the effect will be. Those 2.25 inches might not seem like much, but could mean the differnece between a hit, or a miss at that yardage. And we haven't even begun talking about wind yet, which is much harder to estimate, and much, much more variable. Wind speed at the muzzle might be TOTALLY different than wind speed at the target, and it may change direction and speed multiple times at longer ranges. That's why long range shooters have longer barrels. Velocity. |
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