Help settle a bet: Do AR15s produce a faster velocity than any given .223 rifle?

[BonnieB]

THIS THREAD IS POSTED IN THE WOMEN'S FORUM. GENTLEMEN ARE INVITED TO RESPOND IF THEY ARE CIVIL. IF NOT, PLEASE DON'T. THE WOMEN'S FORUM HAS RULES.


Folks, please help me settle an argument.

BFF and I were having dinner tonight, talking politics and what's-going-on. (She thinks she knows guns because she was raised in Merced and had a .22 and a 30-30 when she was a girl. No further experience that I know about.)

Marj says "The reason that AR15's are so scary is that they produce a much faster velocity bullet than other rifles".

I said "Nope. Velocity is a function of the ammunition. An AR15 and any other rifle using the same .223 ammunition will produce the same muzzle velocity, with some tiny variation from barrel length".

Marj says "Nope. There's something special about AR15's, the striker or whatever, that makes the bullet go faster."

I said "Nope, I don't think there's anything special in AR15's in the way they ignite the round. Being semi-automatic, they do pump out more bullets per minute, but that's not velocity".

So, I asked her to cite her sources, she can't, said maybe an article in the New York Times or on the internet news.

So, I think I'm right, and I'm gonna bet her $100 with a firm handshake deal on the answer. And I DO pay up or collect on my bets, so this has teeth.

The question is "Do AR15's produce faster muzzle velocity than any other type of rifle, assuming you use the same ammo?"

FFS, if I'm wrong, tell me! And regardless of who's right, can you please give me a reliable source of information, not just "Jimmy-joe's website" A manufacturer's opinion would be particularly good.

[Moemoe1]

[superdave50]

You could refer her to any reloading manual, where velocities are listed and cite a specific barrel length tested.

[BonnieB]

Moe, why does the barrel length affect velocity? More spin? Physics isn't my strong suit...

[M1NM]

The AR will be an unmeasureable amount slower given equal barrel length. Why? Because as the bullet gets past the gas port there will be a reduction in pressure since some of the energy is now being used to operate the action. And yes a .22 bullet can be loaded faster than a .30 cal but that's just physics.

[Foothills]

Ballistics

Moe, why does the barrel length affect velocity? More spin? Physics isn't my strong suit...

More time with the expanding gasses pushing on the bullet. Once the bullet leaves the barrel the expanding gases are no longer imparting kinetic energy to the bullet and it starts to slow down. The longer the barrel, the more time the expanding gasses from the gunpowder are pushing on the bullet, and the longer it increases velocity.

http://www.ballisticsbytheinch.com/

[Dvrjon]

Presuming only .223 ammunition is involved, then mv would be the same as other non-AR design firearms.

However, use of 5.56 ammunition (which is more often associated with military style rifles) used in an AR-15 will yield a higher MV than .223. If the AR is chambered for 5.56, the .223 will be slower.

https://gundigest.com/gear-ammo/reloading/ar-15-basics-223-vs-5-56x45-nato

https://www.americanrifleman.org/articles/2013/3/4/223-remington-vs-556-whats-in-a-name/

Here's a comparison of .223 v. 5.56 and barrel length https://rifleshooter.com/2015/12/223...s-to-6-inches/

Check the charts at the bottom and compare ammo/barrel/MV. Heavy bullets stay in the barrel longer, increasing pressure, resulting in higher MV.

So, it's pretty important to get the ground rules established before you make the bet.

[Snoopy47]

If liberals only knew a .308 will produce the same energy at 500 yards as a .223 will at 50 yards.

[russ69]

Probably less velocity than the average hunting rifle with a longer barrel than most AR15 carbines(the most popular AR15).

[mooner760HD]

Moe, why does the barrel length affect velocity? More spin? Physics isn't my strong suit...

Longer barrel provides more space for the expanding gases to drive the bullet velocity up before the bullet leaves the barrel

Edit: oops should have refreshed the thread

[Whiskey_Tango]

Where does the energy come from to cycle the bolt on an AR15? Where does that same energy go on a bolt gun?

[firefly416]

Where does the energy come from to cycle the bolt on an AR15? Where does that same energy go on a bolt gun?

Most AR15s work via Direct Gas Impingement system whereby when you fire off a round, the expanding gases in the barrel exit via a hole in the top of the barrel and are then directed back towards the bolt pushing it back and ejecting the spent brass. The spring then provides an opposite push to the bolt pushing it back to the barrel, picking up a new round, chambering it, and the bolt going into battery and ready to fire.

A bolt gun will have no hole in the barrel for escaping gases to be redirected back to the bolt to move it. Also, your run-of-the-mill bolt action won't allow the bolt to go out of battery until it is lifted up and pulled back.

[FresnoRob]

Lots of good info here OP. I’ll just add at some point a longer barrel begins to hurt the performance. It depends on the amount of gas the round produces.

[Blade Gunner]

THIS THREAD IS POSTED IN THE WOMEN'S FORUM. GENTLEMEN ARE INVITED TO RESPOND IF THEY ARE CIVIL. IF NOT, PLEASE DON'T. THE WOMEN'S FORUM HAS RULES.


Folks, please help me settle an argument.

BFF and I were having dinner tonight, talking politics and what's-going-on. (She thinks she knows guns because she was raised in Merced and had a .22 and a 30-30 when she was a girl. No further experience that I know about.)

Marj says "The reason that AR15's are so scary is that they produce a much faster velocity bullet than other rifles".

I said "Nope. Velocity is a function of the ammunition. An AR15 and any other rifle using the same .223 ammunition will produce the same muzzle velocity, with some tiny variation from barrel length".

Marj says "Nope. There's something special about AR15's, the striker or whatever, that makes the bullet go faster."

I said "Nope, I don't think there's anything special in AR15's in the way they ignite the round. Being semi-automatic, they do pump out more bullets per minute, but that's not velocity".

So, I asked her to cite her sources, she can't, said maybe an article in the New York Times or on the internet news.

So, I think I'm right, and I'm gonna bet her $100 with a firm handshake deal on the answer. And I DO pay up or collect on my bets, so this has teeth.

The question is "Do AR15's produce faster muzzle velocity than any other type of rifle, assuming you use the same ammo?"

FFS, if I'm wrong, tell me! And regardless of who's right, can you please give me a reliable source of information, not just "Jimmy-joe's website" A manufacturer's opinion would be particularly good.

[larkja]

The AR will be an unmeasureable amount slower given equal barrel length. Why? Because as the bullet gets past the gas port there will be a reduction in pressure since some of the energy is now being used to operate the action. And yes a .22 bullet can be loaded faster than a .30 cal but that's just physics.

So to sum it up for you:

1. Velocity will depend on the barrel length, weight of bullet, grains of powder, etc. But all things being equal, a 20" bolt and a 20" AR will effectively have the same velocity leaving the barrel.
2. As M1NM stated above, because a small % of the gas is redirected to the gas port to operate the action, there will be an infinitesimal reduction in velocity, probably only measurable to a percentage of a percentage of a percentage.
3. At some point, barrel length will negatively affect velocity, but I don't know what that would be, and nobody is going around with a 50" barrel.
4. When the cartridge is struck by the pin, it doesn't matter how hard it's struck, only that the primer ignites. So just because an AR might strike harder (no guarantees here) doesn't mean the bullet will have a greater velocity as it leaves the barrel. The pin doesn't push the bullet out of the cartridge, the explosion and expanding gasses do.

Here's the process for your friend:
Pull the trigger --> pin hits the primer --> primer ignites the powder and gasses push the bullet out the barrel --> the longer the barrel (reasonable length here), the longer the gasses are pushing on the bullet and the higher the velocity as it leaves the barrel --> once the bullet leaves the barrel, it is no longer being pushed and will start to slow down.

But, if you really wanted to nitpick her you could say the above points and then add on an AR, a very small % of the gasses are used to cycle the bolt, which doesn't really affect velocity, but statistically, it would actually be a little slower leaving an AR barrel.

So your friend loses either way