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Posted: 3/4/2012 4:31:03 AM EDT
| Would there be a lot of difference in accuracy between a 16" and a 20" barrel on an AR 15 ? |
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Shorter barrels are more accurate.
Why? THEORY! Short = Stiffer with better harmonic resonance. I'd just do a 20 in. and be done with it. especially shooting heavier bullets 68 gr+ with slower powders. effeciant powder burn, better port pressure and dwell time with a 20 over a 16. |
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300 yards? 16" all day. kinda depends on the load. the slower powders with heavy bullets are going to give up more FPS. at or over 200 fps with some powders. RL15 with 75's being one of them. about 3 inches of drop diff. @ 300 yds. between 16-20 tube with a 100 yd. -0 @ .395 B.C. claimed by Hornady for there 75 BTHP. 16 @ 2550 fps 20@ 2750 same load |
I rekon they have some spiffy powder.
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It's not so much the accuracy but the velocity you get from the longer barrel. +1 Shorter barrels are more accurate. Longer barrels can get more velocity. That's not to say that a long barrel can't be accurate. shorter barrel has shorter sight radius and therefore less accurate than a longer barrel unless you use optics. Please explain why you think shorter barrel is more accurate |
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Quoted:
Quoted:
Shorter barrels are more accurate.
Why? THEORY! Short = Stiffer with better harmonic resonance. I'd just do a 20 in. and be done with it. especially shooting heavier bullets 68 gr+ with slower powders. effeciant powder burn, better port pressure and dwell time with a 20 over a 16. you can have a longer yet stiff bull barrel, as long as you tune your load/barrel so that the node of vibration remains at the muzzle, it can be accurate. Anschutz supermatch barrels are 27 inches long and won many Olympic Golds |
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Quoted:
Quoted:
Quoted:
Shorter barrels are more accurate.
Why? THEORY! Short = Stiffer with better harmonic resonance. I'd just do a 20 in. and be done with it. especially shooting heavier bullets 68 gr+ with slower powders. effeciant powder burn, better port pressure and dwell time with a 20 over a 16. you can have a longer yet stiff bull barrel, as long as you tune your load/barrel so that the node of vibration remains at the muzzle, it can be accurate. Anschutz supermatch barrels are 27 inches long and won many Olympic Golds NO Argument from me here!  as far as AR's are concerned I really do feel the IDEAL port pressure for function over various loads is with a rifle length gas system!
you'll notice very little gain in FPS for that spiffy Hornady factory Superformance load between the 20 and 24 inch tube? I'd bet dollars to doughnuts you'd see over 200 fps drop in that load in a 16 inch tube! by the way those are some SERIOUS! fps for a 75 gr. pill in a 20 in. tube! I've popped primers before 2850! with 75's in a 20" 5.56! I've played with 26" tubes in the AR in 5.56 with VLD's  spacegun shit in younger years! LOL
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Quoted:
Shorter barrels are more accurate.
Why? more consistent harmonics First things first...there has been no evidence to support this...in reality consistent harmonics is a function of a consistent forcing function (driven by internal ballistics of a cartridge) as well a the microstructure and residual stresses in the barrel. Either way all of this yields better precision not neccesarily accuracy. At 300 yards ballistic differences will not really play into the ability to hit a target (accuracy) but at longer ranges they will. The precision of these systems (which drives accuracy at these ranges) comes from well manufactured tight tolerances and fitted parts as well as consistent ammunition. Short barrels have an additional factor of higher muzzle pressure that can cause problems durIng launch. In reality the barrel length has little to do with close range accuracy, higher velocity will limit the error of a single aim point from 0-300m due to the flatter trajectory. |
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**Warning - Article contains math, science, applied engineering concepts and facts**
A Look at the Rigidity of Benchrest Barrels By Daniel Lilja It is written in the context of benchrest barrels but it's all relevant. What's the intended use of the rifle? That should drive the decision. |
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