AR Pistol... what length barrel? Pros and cons.

[Hawk]

IMHO:
1. The AR "pistol" is supposed to fulfill a role as PDW which means a compact high capacity weapon.
2. A "PDW" should have more firepower than a handgun and not as much as a full size Assault Rifle.
3. 7.5 inch 5.56 pistols will achieve between 2200-2500 FPS. That's plenty of velocity and punch for the purpose of a PDW
4. Accuracy suffers on a (cheek weld only) AR pistol. I usually practice at 25-35 yards and occasionally out to 50 yards. Based on what it will do at those ranges, I imagine with practice hits on a man size target at 75-100 yards is doable.

If you want a little more velocity than the 7.5" go with a 10.5- 11.5" barrel (2600-2800 FPS) and increased accuracy (200-300 yards) then add a stock and pay the $200 tax to SBR it.

If you want more info on ballistics based on barrel length check out this site: http://ballisticsbytheinch.com/index.html

[Hawk]

for an AR pistol.. IMO anything longer than 8.5 .... is too long.
someone on here said a 10.5" barrel is not really much of a pistol...more like a rifle without a stock

Ha! That was me in another thread.

[Sgt.K]

PS: Here are two AR 15s that I built for two of my sons.

At my level of zoom I see a happy switch on each of those. You're my kinda dad...

[MD66948]

At my level of zoom I see a happy switch on each of those. You're my kinda dad...

Here is the Happy Switch with that POF 7.25" Upper on my Colt M16. https://www.youtube.com/watch?v=L0EnKyS4F70

Dane

[arjohnson]

For 5.56 the shortest I went was 10" on my SCAR, 10.5" and 11.5" on my AR's. If I go any shorter it would be a 300 BO in 8.5".

On a 9mm 4.5"-5.5" is the perfect barrel length, you gain very little ballisticly going any longer that the gains are not worth the added barrel length.

[Emptymag]

I chose a 7.5" because I wanted the shortest possible length. (yeah, I know I could have gotten a 7" barrel)

Once I started factoring in muzzle devices, anything more than an 8" barrel made what I wanted to do pointless - I would end up being not much shorter than my carbine.

A 16" carbine isn't any more compact than an 18" shotgun - neither of which are ideal for maneuvering in a home in my opinion.
Since I HAVE a 16" carbine that won't lose all effectiveness at longer ranges, I don't need to worry about reduced velocities in a pistol - I'm not taking it into combat or shooting zombies in the head at 300 yards - I just want something compact for a specific purpose.

I was told to SBR it. I don't want to. Fuck all that government paperwork.
I was told to go 300 BLK for better performance. I don't want to. Double the price to shoot and I don't want another caliber.

Anyone who wants to challenge the effectiveness within the distance of my living room is welcome to be a test subject - after signing a waiver.

I do like reading these threads though because there's always something I can learn.


EDIT: If 7 inch AR15s are such a BAD idea, why are there thirty thousand pages of pictures of them on arfcom?

[USMC3531]

go 3" for the win

[arjohnson]

I chose a 7.5" because I wanted the shortest possible length. (yeah, I know I could have gotten a 7" barrel)

Once I started factoring in muzzle devices, anything more than an 8" barrel made what I wanted to do pointless - I would end up being not much shorter than my carbine.

A 16" carbine isn't any more compact than an 18" shotgun - neither of which are ideal for maneuvering in a home in my opinion.
Since I HAVE a 16" carbine that won't lose all effectiveness at longer ranges, I don't need to worry about reduced velocities in a pistol - I'm not taking it into combat or shooting zombies in the head at 300 yards - I just want something compact for a specific purpose.

I was told to SBR it. I don't want to. Fuck all that government paperwork.
I was told to go 300 BLK for better performance. I don't want to. Double the price to shoot and I don't want another caliber.

Anyone who wants to challenge the effectiveness within the distance of my living room is welcome to be a test subject - after signing a waiver.

I do like reading these threads though because there's always something I can learn.


EDIT: If 7 inch AR15s are such a BAD idea, why are there thirty thousand pages of pictures of them on arfcom?

It's not that a short barrel 5.56 won't work, anything below a certain length starts to loose it's effectiveness that a different caliber in the shorter length would be better suited by design.

Velocity and energy drastically decrease and chamber pressure drastically increases once you start going below a certain length. This may or may not concern you.

I prefer to get the max for the minimum when it comes to short barrels. I'm building a 8.5" 300 BO for this purpose, I'm not concerned about ammo prices because it's not a gun that will get a lot of use.

I went this direction through research and from advice of people that shoot way more than I do.

[Delkal]

I guess the decision depends if you want to bark more......or bite more.

I can see arguments either way and its really up to the individual. There is no correct answer so the choice is yours.

[Emptymag]

It's not that a short barrel 5.56 won't work, anything below a certain length starts to loose it's effectiveness that a different caliber in the shorter length would be better suited by design.

Velocity and energy drastically decrease and chamber pressure drastically increases once you start going below a certain length. This may or may not concern you.

I prefer to get the max for the minimum when it comes to short barrels. I'm building a 8.5" 300 BO for this purpose, I'm not concerned about ammo prices because it's not a gun that will get a lot of use.

I went this direction through research and from advice of people that shoot way more than I do.

Sure. I'm understanding it all more clearly as I read more.

I'm just of the mind that I understand that the velocity is greatly diminished - it just isn't a factor for what I want the pistol for.

If I had it in my head that I was going to build a 7" 5.56 for killing commies at 500 yards I'd certainly be happy if someone pointed out that I may want to rethink that due to the massive loss of velocity.

I think I'll be OK though if the commies are coming through my back window.