The DISPARITY in 5.56 barrels.

[RandomHero]

The AR-15 industry is saturated with AR-15's, parts, and manufactures. As some believe in longer barrels having more accuracy and penetration, the industry is curving towards many 10.5, 7.5, and 5.5 inch barreled AR-Pistols. If you have any of your own personal test data on this subject via, chronograph, ballistic gel, slow motion video, please share it here to help bring clarification to the debate.
I have attached some articles that bring perspective to the subject matter.

StackPath

Barrel Length Studies in 5.56mm NATO Weapons – Small Arms Defense Journal

www.sadefensejournal.com

 

[xdman]

Well I don't think most of the industry moves because of performance per say. They are quick to move sales on what is hot at the moment. Early 2000's you were into the M4 fad enough that just a couple years ago companies started selling 20 inch barreled A2/A3 type guns again because whats old is new again. Think of the whole Zombie theme, again just a fad to sell stuff when it is hot. Then you get into the brace era and you do get companies and users slowly adopt. You run into ATF opinions. The Fudds start pointing fingers and start yelling see I told you so. At that time braces turned into the latest FU ATF thing......sure I promise I won't shoulder it But it was like a dirty little secret. Then the winds change and the ATF issues another opinion. Well the Cat is now let out of the bag and instead of being essentially only an FU device gets more and more mainstream adoption. It is now almost a challenge to find a gun company who does not offer a brace gun. Well that means sales, accuracy or performance is on the back burner. A prime example a 5 inch 556 AR performance takes a back seat to the coolness factor.

 

[RandomHero]

Well I don't think most of the industry moves because of performance per say. They are quick to move sales on what is hot at the moment. Early 2000's you were into the M4 fad enough that just a couple years ago companies started selling 20 inch barreled A2/A3 type guns. Think of the whole Zombie theme again just a fad to sell stuff when it is hot. Then you get into the brace era and you do get companies and users slowly adopt. You run into ATF opinions. The Fudds start pointing fingers and start yelling see I told you so. At that time braces turned into the latest FU ATF thing......sure I promise I won't shoulder it. Then the winds change and the ATF issues another opinion. Well the Cat is now let out of the bag and instead of being essentially only an FU device gets more and more mainstream adoption. It is now almost a challenge to find a gun company who does not offer a brace gun. Well that means sales, accuracy or performance is on the back burner. A prime example a 5 inch 556 AR performance takes a back seat to the coolness factor.

So are you saying the Springfield PDW 5.5" barrel has low performance?

 

[10mmLife]

Well I don't think most of the industry moves because of performance per say. They are quick to move sales on what is hot at the moment. Early 2000's you were into the M4 fad enough that just a couple years ago companies started selling 20 inch barreled A2/A3 type guns. Think of the whole Zombie theme again just a fad to sell stuff when it is hot. Then you get into the brace era and you do get companies and users slowly adopt. You run into ATF opinions. The Fudds start pointing fingers and start yelling see I told you so. At that time braces turned into the latest FU ATF thing......sure I promise I won't shoulder it. Then the winds change and the ATF issues another opinion. Well the Cat is now let out of the bag and instead of being essentially only an FU device gets more and more mainstream adoption. It is now almost a challenge to find a gun company who does not offer a brace gun. Well that means sales, accuracy or performance is on the back burner. A prime example a 5 inch 556 AR performance takes a back seat to the coolness factor.

Great breakdown!

 

[xdman]

So are you saying the Springfield PDW 5.5" barrel has low performance?

Not necessarily low performance but a different performance curve, when compared to an AR with a longer barrel and built for different purposes.
Now within certain ranges it is still formidable, but half the powder is not burned before the bullet exits the barrel. Are you going to use these guns for elk hunting? No because of the limited performance in that application. As a platform for say something 100yrds and in and the platform is still viable and the pros outweigh the cons for self defense.

Agin remember the popularity trend. AT last years Shot Show Maxim defense released a sweet little kick ass PDW that was super sexy. Everyone lusted over it and since they sold a bunch. Look at this years Shot Show and a bunch of companies followed suit to make sales. I make a prediction that easily removable barrels will be a thing next year. Yes they have existed before, but SA's system is hella cool. And that is the one thing that I saw people with their eyes wide open and chubs in their pants looks at.

Hell I do not blame SA, remember as soon as I saw the pictures of the 2020 line up of SAINTS I was on board you can quote me "wow that as cool as ****", "I need one".

 

[RandomHero]

Not necessarily low performance but a different performance curve, when compared to an AR with a longer barrel and built for different purposes.
Now within certain ranges it is still formidable, but half the powder is not burned before the bullet exits the barrel. Are you going to use these guns for elk hunting? No because of the limited performance in that application. As a platform for say something 100yrds and in and the platform is still viable and the pros outweigh the cons for self defense.

Agin remember the popularity trend. AT last years Shot Show Maxim defense released a sweet little kick ass PDW that was super sexy. Everyone lusted over it and since they sold a bunch. Look at this years Shot Show and a bunch of companies followed suit to make sales. I make a prediction that easily removable barrels will be a thing next year. Yes they have existed before, but SA's system is hella cool. And that is the one thing that I saw people with their eyes wide open and chubs in their pants looks at.

Hell I do not blame SA, remember as soon as I saw the pictures of the 2020 line up of SAINTS I was on board you can quote me "wow that as cool as ****", "I need one".

I have been exposed to and used the 5.56 round for many years. In all of my travels, people I have encountered, and research I have done, I have never ever heard or known of anyone hunting "Elk" with a 5.56 round. No matter what barrel size. The 5.56 is not designed for "Elk". So poor analogy for performance there and can't see were hunting "Elk" would come into conversation based on 5.56 barrel lengths of 10.5" or less.

I included links to real tests that were conducted and submitted to the public. Looking to get responses from people that have hands on data through chronograph, ballistic gel, slow motion video that can articulate their test results to bring clarification to the debate for those that may not have any experience in this area.

 

[RandomHero]

Anyone in here have a 5.5" barrelled AR pistol?

 

[Ginge]

Short barrels will vary on their velocities, but they should all be relatively close. 5.56 loses its tumbling and yaw effect at around the 2200 fps mark, and then basically become a 22 hornet. The pdw from SA and the Evac will likely be good to around 70 ish yrds for the bullet to do its thing. Its a purpose built weapon. I believe the 10.5 and 11” Colt commando shorties offered the best balance of range and shortness. The last article I read on them they were good to about 200+ before velocity dropped off and it became a mobile ice pick.

Ammunition will play a roll in the fighting snubbies. Id limit it to 55 m193 or the 62 M855 to keep up the velocity.

To me, they fall into the just above smg category. Limited range and a loud boom and big flash. They fill a specific role.

 

[BET7]

Not necessarily low performance but a different performance curve, when compared to an AR with a longer barrel and built for different purposes.
Now within certain ranges it is still formidable, but half the powder is not burned before the bullet exits the barrel. Are you going to use these guns for elk hunting? No because of the limited performance in that application. As a platform for say something 100yrds and in and the platform is still viable and the pros outweigh the cons for self defense.

Agin remember the popularity trend. AT last years Shot Show Maxim defense released a sweet little kick ass PDW that was super sexy. Everyone lusted over it and since they sold a bunch. Look at this years Shot Show and a bunch of companies followed suit to make sales. I make a prediction that easily removable barrels will be a thing next year. Yes they have existed before, but SA's system is hella cool. And that is the one thing that I saw people with their eyes wide open and chubs in their pants looks at.

Hell I do not blame SA, remember as soon as I saw the pictures of the 2020 line up of SAINTS I was on board you can quote me "wow that as cool as ****", "I need one".

Yup, agreed xdman. The SA EVAC is cool & I concur that like type products will probably be the next big thing next year. I see it continuing with different calibers as well.

 

[RandomHero]

Yes I have shot a 7.5 and it was crazy accurate from 3-25 yards. Never had a chance to shoot it at further distances. I however have seen videos on YouTube where a 4" barrelled AR-pistol key holed rounds at 15 yards. Since I have no experience in a 5.56 round in a barrel shorter than the 7.5" it would be beneficial to hear from first hand experience. Thanks for the input.

 

[Ginge]

Keyholing can be caused by a few things. Twist rate vs bullet weight, bore size too large (seen this on a Polish tantal) and chambers not being cut properly causing the bullets to enter the barrel off center. Even bullets can be off by .001”, and can have a negative effect on how it stabilizes.

The one has more affects on accuracy than people realize, is the chamber, and throat erosion to a certain degree will determine if a barrel is indeed shot out.

 

[RandomHero]

Keyholing can be caused by a few things. Twist rate vs bullet weight, bore size too large (seen this on a Polish tantal) and chambers not being cut properly causing the bullets to enter the barrel off center. Even bullets can be off by .001”, and can have a negative effect on how it stabilizes.

The one has more affects on accuracy than people realize, is the chamber, and throat erosion to a certain degree will determine if a barrel is indeed shot out.

Thanks If the rifling does not reach a full rotation I know that can cause it as well. You have any video, or data you can share?

 

[Ginge]

Thanks If the rifling does not reach a full rotation I know that can cause it as well. You have any video, or data you can share?

Yes. If the chamber is to blame, erosion the throat and beginning of the leade will get larger, changing tolerances and allowing the bullet to do things it normally doesn’t.

This is a good quick read on chambers being improperly done.

Chamber Throats 101 - A basic on the importance of a firearms throat

From the pages of The IHMSA News, Shooting sports, hand gun, ammo, cartridges, xp 100, reloading, firearm, cast bullet, bullet casting and more information articles

www.lasc.us

This is too.

freebore, throats and bullet jump – Atlantic Shooting School

This is good for 5.56 velocity from 26”-6” barrels.

223 Remington/ 5.56mm NATO barrel length and velocity: 26 inches to 6 inches

Have you ever wondered how much barrel length effects muzzle velocity on your rifle? Well I did, so I cut up rifles chambered in 223 Remington, 308 Winchester, 7 mm Remington Magnum and 300 Winche…

rifleshooter.com

Finally, the twist rate test vs bullet weight in 5.56 and .223.

AR-15 Barrel Twist Rates - What You Need To Know

Tom explores the importance of AR-15 Barrel Twist Rates. What can go wrong & what can go good.

www.ammoland.com

Hope this help.

 

[RandomHero]

Yes. If the chamber is to blame, erosion the throat and beginning of the leade will get larger, changing tolerances and allowing the bullet to do things it normally doesn’t.


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This is a good quick read on chambers being improperly done.

Chamber Throats 101 - A basic on the importance of a firearms throat

From the pages of The IHMSA News, Shooting sports, hand gun, ammo, cartridges, xp 100, reloading, firearm, cast bullet, bullet casting and more information articles

www.lasc.us

This is too.

freebore, throats and bullet jump – Atlantic Shooting School

This is good for 5.56 velocity from 26”-6” barrels.

223 Remington/ 5.56mm NATO barrel length and velocity: 26 inches to 6 inches

Have you ever wondered how much barrel length effects muzzle velocity on your rifle? Well I did, so I cut up rifles chambered in 223 Remington, 308 Winchester, 7 mm Remington Magnum and 300 Winche…

rifleshooter.com

Finally, the twist rate test vs bullet weight in 5.56 and .223.

AR-15 Barrel Twist Rates - What You Need To Know

Tom explores the importance of AR-15 Barrel Twist Rates. What can go wrong & what can go good.

www.ammoland.com

Hope this help.

Absolutely great info.

 

[Ginge]

I would have responded sooner, but I had to find the links I had saved in my favorites on my iPhone. Theres over 800 so it took a minute. Lol. I hope you find this information as useful as I do!

 

[RandomHero]

I would have responded sooner, but I had to find the links I had saved in my favorites on my iPhone. Theres over 800 so it took a minute. Lol. I hope you find this information as useful as I do!

Yes it does help. It is well appreciated Ginge I was just trying to get clarification on how far a 5.5" barrelled AR-pistol will shot without key holing the round, and if at all.

 

[Ginge]

Sweet!

 

[TEXASforLIFE]

Thanks If the rifling does not reach a full rotation I know that can cause it as well. You have any video, or data you can share?

As in a 1/7 needs 7" and 1/8 needs 8" and so on for full rotation!

 

[RandomHero]

As in a 1/7 needs 7" and 1/8 needs 8" and so on for full rotation!

So basically what your saying is anything shorter than a 7 1/2" barrel AR pistol doesn't have the length to complete one full rotation to stabilize the round. Therefore it will not have point of aim point of impact. As well as key hole the round.

 

[TEXASforLIFE]

So basically what your saying is anything shorter than a 7 1/2" barrel AR pistol doesn't have the length to complete one full rotation to stabilize the round. Therefore it will not have point of aim point of impact. As well as key hole the round.

If the barrel length is shorter than the twist, then yes it will not make a complete rotation!