Building a 9mm AR w/16" barrel - Bullet Velocity Question

[garandman]

Not wanting to bother with an SBR but still wanting to take full advantage of the 9mm cartridge, led me to decide on a 10.5" pistol build.
This configuration has proven to be ideal for something appropriate for home defense, with a little more firepower than the typical handgun.

IMO... the 9mm even from a 16" bbl doesn't have enuf power for anything but a home self-defense round.

The advantage of your 10" pistol build or my SBR is not really in having more power than a handgun, but in the added stability and accuracy of a pistol w/ brace or a SBR. While less maneuverable than a handgun, it is more accurate than a handgun, esp. under stress, and more ammo capacity, and is more maneuverable than a 16" carbine.

To me, a 9mm 16" carbine really doesn't do anything particularly well, other than a range plinker toy. Which can be reason enuf to own / build one.

 

[Oso]

When I built one it was before it became the rage and everyone started offering/selling or cloning. Mine actually has a Hahn Mag Block and uses Uzi stick mags. It is everyone's favorite range toy...6.5" barrel and suppressor all inside the handguard. It is as quiet as a suppressed 22.... the sound of the buffer spring moving back and forth became deafening...replaced it with JPE Silent capture spring. It is purely a toy.

What made me decide on an AR9 is the availability of universal parts. Back then I was concerned about availability of parts and repairs for the one-off specialty models. If I did it today then I would look hard at the CZ Scorpion. Now if FN would just make a PS90 in 221Fireball.....

 

[ckaberna]

@RJTodd

May want to weigh in on this discussion, he’s an old pro. Lol

 

[miningshawn]

I'm thinking about building a 9mm AR for my fiancé, (and for me of course lol), and I' m thinking about the possibility of a loss in muzzle velocity when shooting a pistol round through a 16" barrel. Does anyone here have experience with a 16" barrel shooting 9mm ammo? If so, was there a loss in muzzle velocity compared to a pistol?

Thanks in advance.

Lou

I didn't really see a quantitative answer in this thread, so here goes.

I just ordered a PSA AR9 with a 16" barrel. I will pick it up in 2 weeks. I will take the AR9, a G26, a P320, and an M9 to the range and chrono some loads in all of them, (115, 124, and 147 grain ready to go). A 3", 4", 5" and 16" comparison.

I am also curious - does the 9mm with a 16" barrel have a slower or faster muzzle velocity? Does projectile weight matter in slowing down/speeding up?

 

[RJTodd]

Muzzle velocity will be higher. How much depends a lot on the type of load. Heavy defense loads with slow powder can pick up a lot. Will post a link that give lots of data. Standby

 

[RJTodd]

Here ya go. This will give enough reading for a headache. Good work by the author.

BBTI - Ballistics by the Inch :: 9mm Luger Results

(statement of intent)

www.ballisticsbytheinch.com

 

[Oso]

The take away from the report is the using factory +P/Defense ammo (hot loads) you can expect on average an 11% increase (137fps) in velocity when using a 16" barrel compared to a 5" barrel. I don't really call that significant improvement... only 137fps increase on average with an additional 11" of barrel (3.2x longer barrel). The velocity differential diminished as the bullet weight increases.

If you plan to shoot reloads then the results will be even less significant as most reloads are lighter charge weights than the +P factory ammo that was tested. With softer loads there is a good chance that the velocity out of 16" barrel will be lower than 5" barrel. To what degree will all depend upon how much lighter the powder charge and what weight bullet used in your reloads.

 

[skeeljc]

A 16" 9mm AR (PCC) will pick up about 200 fps over a 4" to 5" pistol.

 

[ckaberna]

The take away from the report is the using factory +P/Defense ammo (hot loads) you can expect on average an 11% increase (137fps) in velocity when using a 16" barrel compared to a 5" barrel. I don't really call that significant improvement... only 137fps increase on average with an additional 11" of barrel (3.2x longer barrel). The velocity differential diminished as the bullet weight increases.

If you plan to shoot reloads then the results will be even less significant as most reloads are lighter charge weights than the +P factory ammo that was tested. With softer loads there is a good chance that the velocity out of 16" barrel will be lower than 5" barrel. To what degree will all depend upon how much lighter the powder charge and what weight bullet used in your reloads.

Heck, test it and see! Then report back.
simple as that

 

[skeeljc]

My 16" PCC that I use for Steel Challenge runs well with 124 grain plated bullets loaded at 950 fps with HS-6.

 

[Oso]

No shit.

Totally not necessary...

The OP didn't give any indication of how he plans to feed the gun. There is a world of difference between factory ammo, especially +P ammo, and typical reloads. Also, there is a myriad of off-brand, small batch "factory" ammo (budget friendly plinking) in the market that are loaded at lower velocities, which may in turn slow down in a 16" barrel.

The definitive test results were based on a limited ammo group, consisting of the most powerful of 9mm loads. You and I may immediately recognize this, but a less experienced shooters or new reloader may not immediately draw the distinction and assume this velocity gain is a constant for all ammo.

Yes - ultimately the only way to know is to test a specific load.

 

[ckaberna]

Totally not necessary...

The OP didn't give any indication of how he plans to feed the gun. There is a world of difference between factory ammo, especially +P ammo, and typical reloads. Also, there is a myriad of off-brand, small batch "factory" ammo (budget friendly plinking) in the market that are loaded at lower velocities, which may in turn slow down in a 16" barrel.

The definitive test results were based on a limited ammo group, consisting of the most powerful of 9mm loads. You and I may immediately recognize this, but a less experienced shooters or new reloader may not immediately draw the distinction and assume this velocity gain is a constant for all ammo.

Yes - ultimately the only way to know is to test a specific load.

Your right.
post deleted. Sorry.