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What distance can you accurately shoot an AR-pistol with a 1:7 twist?

RandomHero

RandomHero

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It has been said that when you reduce barrel length, that you sacrifice accuracy. What is the farthest you have accurately shot a 7.5" AR-Pistol?
 
So first off, that old saw is an urban myth. By shortening the barrel you gain barrel rigidity and mechanical accuracy from reducing barrel whip and harmonics, assuming you have the right bullet and twist rate for the length. You do loose velocity, and how much depends on the cartridge, not on the barrel length. That changes the distance your bullet goes subsonic and environmental factors start to really push it around, but its not any less accurate.

Assuming you are talking about a 5.56, then its going to depend if you want lethality (and what you consider that to be in foot pounds per square inch) at range or just punching paper? I don't run 5.56 guns shorter than 10.5 because you loose so much velocity below that it gets into 5.7 fired from a subgun territory.

Having said that, at the range from a braced position I can get solid hits on a IDPA torso plate at 300 yards. My short AR's usually live with only a red dot and serve the role of a modern SMG. I have never felt the urge to try to drive it faster or further. You loose so much velocity in that caliber that I doubt most rounds have much lethality left at that range, even thought it will still ring steel and get someones attention.

On paper my setup will give me over 300 ft/lbs well past 500 yards. Thats a 69 grain bullet leaving my 10.5" barrel at 2540 FPS. By going with a 3" shorter barrel your lethality (which I define at about 300 ft/lbs or the kinetic energy of a 9mm, but a much smaller hole) tops out just before 400 yards. On paper. Barrel, wind, environmental conditions, etc. all play a part.
 
Epeeist said:
So first off, that old saw is an urban myth. By shortening the barrel you gain barrel rigidity and mechanical accuracy from reducing barrel whip and harmonics, assuming you have the right bullet and twist rate for the length. You do loose velocity, and how much depends on the cartridge, not on the barrel length. That changes the distance your bullet goes subsonic and environmental factors start to really push it around, but its not any less accurate.

Assuming you are talking about a 5.56, then its going to depend if you want lethality (and what you consider that to be in foot pounds per square inch) at range or just punching paper? I don't run 5.56 guns shorter than 10.5 because you loose so much velocity below that it gets into 5.7 fired from a subgun territory.

Having said that, at the range from a braced position I can get solid hits on a IDPA torso plate at 300 yards. My short AR's usually live with only a red dot and serve the role of a modern SMG. I have never felt the urge to try to drive it faster or further. You loose so much velocity in that caliber that I doubt most rounds have much lethality left at that range, even thought it will still ring steel and get someones attention.

On paper my setup will give me over 300 ft/lbs well past 500 yards. Thats a 69 grain bullet leaving my 10.5" barrel at 2540 FPS. By going with a 3" shorter barrel your lethality (which I define at about 300 ft/lbs or the kinetic energy of a 9mm, but a much smaller hole) tops out just before 400 yards. On paper. Barrel, wind, environmental conditions, etc. all play a part.
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Thank you for all the information. I appreciate it.
 
I don't have anything less than a 1/8 on a pistol platform. I have 2 300bo 1/8 @8 1/2" and 1 556 1/8 @ 11 1/2" and haven't shot passed 200 on either!
 
IMHO the 300bo wasn't made for accuracy, unless it's within 50 yards. The original is the whisper and made for that. Sub loads for cqb!
 
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