What is the best AR-15 barrel length—and are ultra-short 5.56 rifles actually useless?
James visits the FBI’s Ballistic Research Facility to speak with veteran FBI ballistician Robert about AR-15 barrel length, projectile weight, velocity, twist rate, fragmentation, expansion, and terminal performance.
Robert explains why muzzle energy alone tells you very little, why the FBI prefers expanding projectiles over traditional fragmenting ammunition, and how every bullet has an optimal performance window. Depending on the ammunition and intended distance, a longer barrel can even drive a projectile too fast and produce worse terminal performance at close range.
We also get direct answers on the practical differences between 7.5-, 11.5-, 14.5-, 16-, 18-, and 20-inch AR-15 barrels. For law enforcement and home defense, Robert identifies an 11.5-inch barrel with a 1:7 twist and a properly selected 64- to 75-grain bonded projectile as the practical sweet spot. He also explains why 7.5-inch 5.56 rifles are not necessarily worthless—provided their ammunition and engagement distance are properly matched.
This is not internet theory. It is a detailed discussion of actual projectile testing, terminal-ballistics standards, and the variables that determine whether a 5.56 round performs as designed.
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Bonded soft points will always perform better through barriers which is something that wasn't mentioned as being important for law enforcement purposes.
Oh, come on do an honesty check.. Ask him CK was shot by a 3006
The things that appeal to me about the 20" is not just about velocity and effective range. It's the rifle length gas system running smooth and being easy on internals offering the best longevity to an AR. It's having the most proven long term reliability you can have for a D.I. AR. You have a super low recoil impulse as is and don't have as much concussion since it's not a shorter barrel. Choosing ammo is important, but also doesn't matter as much with a longer barrel. And when ammo matters most, I trust the extra velocities gained to give me the best chance against barriers and armor.
But for room clearing teams, an 11.5" AR makes a lot of sense and especially when adding on silencers to the muzzle.
Or you could use an AUG. 👌
Great. 24 inch barrel with a 1/14 twist and 100 grain bullet. Im all set. Thanks James
This is stupid every answer is it depends most people run a 16 inch 1:7 run a soft point Speer move the fuck on fucking yap
16 inch guys hate this video😂
Good thing I just bought a 10.3 upper!
No two chambers,barrel,barrel ends are never the same
I could listen to this man preach his craft as my sole source of entertainment. His knowledge of the topic is palpable. Thank you for this video.
I've reloaded my own ammo for 45 years and I found the work up load is indispensable
So is 55 grain fmj just useless spitballs?
Everyone knows the magic length is 12.5 inches. It keeps the velocity above 2,600 fps, and it has a good dwell time, and fragmentation.
5:30 you have to shoot a bag of oranges
Pretty sure I'm going to trust the actual designer of the weapons system over this guy or any fool on the Internet.
Stoner didn't design the AR-15;
Jim Sullivan did.
Hence not going past 2 minutes in this video.
20" .
That's what the rifle and cartridge was designed to work with.
Beating a dead horse ! If I shoot you with a 7.5 or a 10.5 or a 14.5 it will still kill you period ! Not one person in a suburban neighborhood you will not shoot out to 50 to maybe 100 yards !
The fbi says a lot of things, is this what they're supposed to be "investigating?" 😂
I bought a 12.5 before Colorado’s rifle ban.
I really don't think anyone should take recommendations from that Alphabet agency, They think a 30-6 Was what took out Our Brother Charlie. JUST SAYIN..
One thing I may have missed but I think wasn’t mentioned, is that while yes 11.5 is all most people need, if you aren’t going to suppress the gun, 14.5 or 16 really isn’t that long, it’s plenty maneuverable for an officer or home defense, you gain 300-400 yard performance, which you may not need, but why not. It also gets the muzzle blast further from your ear which does make a difference in hearing damage, although suppressor is obviously miles better on that, but maybe your department isn’t going to issue or allow them, or maybe your state bans it or you simply just don’t want to do the tax stamp. If so I say just go 14.5 pinned or 16 personally. That’s gonna be the same length as an 11.5 suppressed anyway.
Are you interview the FBi or MI6. Dudes accent is throwing me off
10.5 inches is the shit. I wouldn't use it if it didn't perform well . I literally love pissing off fuds at the range when I'm tagging center of mass at 200-300 yards with a red dot .
Don't let brassfacts see this video that dmr conversation is gonna make him happy
Great episode, thank you for sharing.
This guy should really just commit to being bald at this point.
A minute into this I just knew he was gonna say 11.5" with a bonded soft point 64gr with true 5.56, not .223, power. I have a hard time believing that barrel length is going to hurt my performance in anything other than weight and maneuverability. Hitting a hog or deer inside 100 yards with the LE 64gr bonded soft points that I have always seem to perform better with 18 and 20". Its hard for me to imagine that even with that expanding perjectile that performance suffers. I understand that the more it expands the less penetration it MIGHT have but I think energy and temporary stretch cavity matter as well. As long as it penetrats enough to reach heart, liver, lungs ect energy on target are a thing. Otherwise I might as well use my 5.7x28mm AR with projectiles that will penetrate and call it a day.
12.5 master race.