5.56 Pistol-What's the best barrel length.?

[850guns]

So, I'm putting together a multi-caliber pistol. I have a factory 300 BO pistol. I have since purchased a CMMG Banshee 300 barrel in 9mm. Looking to get their 22 upper as well. I also want a 5.56 upper. But I don't know what length barrel to get. It will be suppressed. I want as short as possible, Without sacrificing reliability and velocity.

What length barrel do you recommend and why?

 

[SAWMAN]

Soooooo . . . . lemme see if I understand. You want the AR bbl "as short as possible" but do not want to sacrifice any velocity ?? Do I understand that right ??
Even with surpressor,go no shorter than 10.5" bbl. The velocity loss would be HUGE !! --- SAWMAN

 

[850guns]

Well, i know there's going to be a velocity drop. How much is too much? I have heard the shorter it is, the more wear and tear/ less reliability. This won't be a 500 yard pistol. More of a range toy. But I still want accuracy and reliability. Thanks for the recommendation. I know i don't want a 14.5" barrel. Just not sure how short to go.

 

[Dan1612]

Somewhere between 11 and 12 will give you the best short barrel reliability. A5 buffer would make it so you don’t have to use an adjustable gas block to go suppressed and unsuppressed if you don’t want to mess with adjustments so you’re not hugely overgassed when suppressed. Velocity should be around 2700 with factory 5.56 ammo. I’ve hit 700 with my 11.3, just gotta know your holds.

 

[Murfpcola]

I did some research a few years ago when I was looking for a pistol. Most of your big name entry level companies sell 10.5” barreled uppers with carbine length gas and they are generally reliable. I wanted an 11.5” but could not find one in my budget with the 11.5” barrel. I read that the 11.5” has 40% more dwell time than 10.5”. So in theory the 11.5 is more reliable. Dwell time is the time between the bullet passing the gas port and exiting the barrel. During this time the gases are going into the gas tube cycling the action.

As far as velocity, I read that .223 keeps gaining speed all the way up till about 22” barrel length.

I have no experience with suppressors. Maybe my rambling will help

 

[Daezee]

You said it will be suppressed. That being the case, instead of getting a short bbl first, look at the suppressor first. How short of bbl does the suppressor maker say the suppressor you want will safely handle? That will be a big part of your answer as to bbl length.

 

[Dan1612]

Most solid suppressors are rated for 10.5. However, I would not go that short. Reliability suffers unless you set it up with a heavy buffer so it’s not hugely overgassed when suppressed, and if so commercial 223 may not have enough power to reliably cycle depending on gas port size.

I reiterate, 11-12” is your ticket, preferably with an A5 buffer. I’ve been running mine harder than most for going on 5 years now and it’s still my favorite rifle for general use. Mine does have an adjustable gas block, but that’s not strictly necessary with this particular setup.

 

[850guns]

Oh, that reminds me: i am also hoping to only use 1 buffer system for the different calibers. I own 2 pistol lowers. The one i prefer to use in this build has a folding stock system. This should add weight to the Buffer system, and possibly increase reliability?

 

[850guns]

Oh, and no barrel restrictions on my suppressor. Dead Air Nomad 30

 

[Dan1612]

You can use a folding stock with A5 buffer, just swap one tungsten for steel compared to what you’d use since the spacer adds about the same difference in weight. A5 will also give you more reliability across the different calibers from having a longer, more forgiving spring. You can google-fu more as to why that is.

 

[Dan1612]

Even if you just start with the barrel, with a DI system, an 11-12 will give you the most reliability for the shorter length.
Just go with that and take it from there, tuning accordingly as you go. That length will set you up for success with less headaches.

 

[850guns]

I will be using an adjustable gassystem.
Thanks for all the replies.

 

[Daezee]

Oh, and no barrel restrictions on my suppressor. Dead Air Nomad 30

Well, I am impressed with the specs I just looked up. I still bet the blast baffle will be eaten by the effect of the muzzle blast of unburnt powder and pressure.

The 7.5" was reliable, once I figured one thing out. After not many rounds it would have failures to extract the fire case from the chamber. With the short bbl and thus the short distance of the action/chamber from the gas port, more unburnt/partially burnt powder was being blown back into the action getting on the top rounds in the magazine than a longer bbl would do. The dirty rounds would chamber, but fail to extract due to the unburnt powder getting in the chamber and building up. You could see the dents in the fired cases from the powder particles stuck in the chamber. Clean chamber, and all would be OK for 30-40 rounds. No, new extractor and extra power extractor springs didn't help, just ripping the rim off the case, only chamber cleaning with a brass brush would be the fix. Experimenting with powders, I found WW748 would run cleaner than 844 and 846 in the 7.5" bbl, letting it go a few hundred of rounds before cleaning. 2200 ran even cleaner, but I didn't get the accuracy I wanted. I've never fired it suppressed because my 2 suppressors are not rated for that short of a bbl, but suppressors are known to blow back more gunk back into the chamber/action....

The shortest .223 AR bbl I have is 7.5". Using "medium" (not low power; not "full" power) reloads with 55gr bullets, my 7.5" gives 1900fps. One 10.3" bbl gives 2345fps. One 16" bbl gives 2740fps.

On my Daniel Defense 10.3" bbl, adding a linear comp instead of their standard A2 flash hider caused failures to extract. Linear comp was increasing the gas port pressure, causing the BCG to go back faster before the chamber pressure was reduced enough to allow extraction. Midwest Industries told me their Blast Diverter linear comp did not increase port or back pressure. They were right, it functioned perfectly. I like to add some type of linear comp on shorter bbls to reduced the muzzle blast to make it easier on my fellow shooters and myself. I am confident my DD 10.3" bbl would not play well with a suppressor attached unless the gas port hole could be reduced in diameter.

Not the best pic, but you can see the inside of a steel linear comp being eaten away on a 7.5" bbl after 1709 rounds. I fire 5 shots and let cool, so it doesn't get as much heat as from rapid fire. I do not know the makeup of the comp other than it's steel. You should only see a smooth roundness. KAW Valley says:
Weight: 2.9 oz
Heat Treatment: Melonite QPQ
Surface Finish: QPQ Black

 

[850guns]

Great stuff. So will a suppressor increase dwell time?

 

[OldMan]

So, I'm putting together a multi-caliber pistol. I have a factory 300 BO pistol. I have since purchased a CMMG Banshee 300 barrel in 9mm. Looking to get their 22 upper as well. I also want a 5.56 upper. But I don't know what length barrel to get. It will be suppressed. I want as short as possible, Without sacrificing reliability and velocity.

What length barrel do you recommend and why?

I love mine... 11 in faxon gunner... very light ,one in 8 twist..

 

[Daezee]

Great stuff. So will a suppressor increase dwell time?

Yes, but you will have an adjustable gas block to moderate that via increasing or decreasing the amount of gas you let flow back to contact the bolt carrier. More important on a shorter bbl in my opinion. Yes I use two adjustable gas blocks. One on a 10.5” and one on an 8”...both are 300 Blackout though. 8” same gas setting for suppressed and non suppressed...go figure. 10.5” uses different settings for suppressed and unsuppressed, subsonic and supersonic.

 

[wildrider666]

Folks often say its for 5.56 but often shoot a lot of cheaper .223. There's a couple hundred FPS difference at various lengths: pic your poison. Shorter barrels are a economic waste of ballistic potential that your paying for with each cartridge fired. With similar cartridges the 5.56 produced more velocity for a given length BUT if we look at a 14 inch .223 providing 2808 FPS and a 11 inch 5.56 providing 2834 FPS: one is a cheaper cartridge to use while getting very close preformance. You can see this comparison on tables at the Link below. Either way, the shorter the barrel, the poorer the combustion/burn will be: the more fouling will be deposited in the direct impingement system, the Upper/Lower receiver and your Suppressor. Does the Nomad 30 have removable baffles for cleaning? Nothing in the Nomad 30 manual on cleaning other than threads.

How much velocity you want to give up?

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

I'm not a short barrel hater, I have a 10.5 and enjoy it. I'm just passing info/concerns for your consideration. I'm not a multiple uppers (1/2 guns) for one lower fan. I hope it/they turn out great.

 

[850guns]

The nomad is tubeless. But the end caps can be changed. Its the transformer of suppressors.

 

[850guns]

Well, I am impressed with the specs I just looked up. I still bet the blast baffle will be eaten by the effect of the muzzle blast of unburnt powder and pressure.

The 7.5" was reliable, once I figured one thing out. After not many rounds it would have failures to extract the fire case from the chamber. With the short bbl and thus the short distance of the action/chamber from the gas port, more unburnt/partially burnt powder was being blown back into the action getting on the top rounds in the magazine than a longer bbl would do. The dirty rounds would chamber, but fail to extract due to the unburnt powder getting in the chamber and building up. You could see the dents in the fired cases from the powder particles stuck in the chamber. Clean chamber, and all would be OK for 30-40 rounds. No, new extractor and extra power extractor springs didn't help, just ripping the rim off the case, only chamber cleaning with a brass brush would be the fix. Experimenting with powders, I found WW748 would run cleaner than 844 and 846 in the 7.5" bbl, letting it go a few hundred of rounds before cleaning. 2200 ran even cleaner, but I didn't get the accuracy I wanted. I've never fired it suppressed because my 2 suppressors are not rated for that short of a bbl, but suppressors are known to blow back more gunk back into the chamber/action....

The shortest .223 AR bbl I have is 7.5". Using "medium" (not low power; not "full" power) reloads with 55gr bullets, my 7.5" gives 1900fps. One 10.3" bbl gives 2345fps. One 16" bbl gives 2740fps.

On my Daniel Defense 10.3" bbl, adding a linear comp instead of their standard A2 flash hider caused failures to extract. Linear comp was increasing the gas port pressure, causing the BCG to go back faster before the chamber pressure was reduced enough to allow extraction. Midwest Industries told me their Blast Diverter linear comp did not increase port or back pressure. They were right, it functioned perfectly. I like to add some type of linear comp on shorter bbls to reduced the muzzle blast to make it easier on my fellow shooters and myself. I am confident my DD 10.3" bbl would not play well with a suppressor attached unless the gas port hole could be reduced in diameter.

Not the best pic, but you can see the inside of a steel linear comp being eaten away on a 7.5" bbl after 1709 rounds. I fire 5 shots and let cool, so it doesn't get as much heat as from rapid fire. I do not know the makeup of the comp other than it's steel. You should only see a smooth roundness. KAW Valley says:
Weight: 2.9 oz
Heat Treatment: Melonite QPQ
Surface Finish: QPQ Black

View attachment 91202 View attachment 91203

Lots of great info/feedback thanks!

 

[850guns]

My 7.5 300 blaclkout will not cycle subsonic with just a birdcage. (S&B)
My 16" 308 will not cycle subsonic with a can, i didn't try it without a can. (PPU)