View Full Version : Optimal 9mm AR barrel length?
Does anyone know what the optimal barrel length is for 9mm rounds for max velocity?
Say, standard 115gr FMJ rounds for start.
I know different loads could change optimal barrel length but anyone have a ballpark?
I was just wondering if it was in SBR range or if the 16" was getting close.
Thanks in advance.
I thought I read somewhere that 10.5" was optimum for 9mm ?
I may be wrong though.......
Hard to get a deffinitive answer on that. Many people base it on what companies do such as an MP-5 is in the 8" range I think.
I just searched and searched and can't find a good site with velocity specs to compare. Lots of charts out there but they're all different loads with different barrel lengths.
One site quoted a PMC test done on penetration not velocity. It said something to the effect that extremely short barrels that don't produce enough velocity will penetrate further because the bullet won't expand.
Another chart I saw was purely built off theoretical numbers. Velocity was graphed rising all the way to the end of the chart at 16". The criticism it brought on was that at some point the length of the barrel causes friction and it should drop off.
I guess until someone chrono's the same ammo from 16" and cuts/re-crowns an inch at a time, we'll never know.
JeepDriver
12-04-06, 16:31
I have a 9.25" TOS barrel on one of my SBR's and It's every bit as accurate out to 25yards as the 16" guns. I can shoot it out to 75 yards easily hitting a 12x12 steel plate.
I don't know about velocities in the 9.25" barrel, but the 16" barrels I chronoed a while back were only running 100 to 150 fps faster.
WWB VP was averaging 1269,
Ranger 127+P+ was 1401,
Golden Saber 124+p was 1277,
Speer 124 +P was 1418 (and the most consistiant),
Federal Hydra Shok 124gr was 1207,
Mag tech 115gr was 1237.
I keep a mag of Ranger 127+P+ loaded, not that I'd grab the 9mm AR for defence, But It's nice to have a mag ready ;)
I tested this a couple of years ago with a 5", 10.5", and 16" barrel.
Ammunition used was the same, though I can't remember if it WWB or Magtech.
I'll have to search my PC for the results, but if I remember correctly statistically there was little difference between the 10.5" or 16" barrel. While I did not measure accuracy to the fractional inch. Both barrels where equally accurate out to 100 yards from the bench with iron sights.
Will subsonic 147gr. stay subsonic out of a 10.5" 9mm barrel if it is out of a pistol barrel?
Sorry to dredge up an old thread, but my search didn't yield the results I was looking for...
Will subsonic 147gr. stay subsonic out of a 10.5" 9mm barrel if it is out of a pistol barrel?
I'm looking for an answer to this question as well.
To be more specific, what is the best length for a barrel while still keeping the bullet subsonic? I'm trying to decide on whether to get a 5" or 7" threaded barrel from Spikes and plan on shooting 147gr. Federal HST out of my SBR. My concern is that the 7" barrel may be enough for the round to go supersonic. Am I justified or is it a non-issue?
I'd like to have the extra two inches if it might eke out a couple hundred more fps, but won't if it'll mean losing out on the effectiveness of the Ti-RANT.
Try this site:
http://www.ballisticsbytheinch.com/9mmluger.html
Looks to me like 12 inches is where the curve flattens out for most types of 9mm ammo.
Sorry to dredge up an old thread, but my search didn't yield the results I was looking for...
I'm looking for an answer to this question as well.
To be more specific, what is the best length for a barrel while still keeping the bullet subsonic? I'm trying to decide on whether to get a 5" or 7" threaded barrel from Spikes and plan on shooting 147gr. Federal HST out of my SBR. My concern is that the 7" barrel may be enough for the round to go supersonic. Am I justified or is it a non-issue?
I'd like to have the extra two inches if it might eke out a couple hundred more fps, but won't if it'll mean losing out on the effectiveness of the Ti-RANT.
A 3 to 4 inch barrel is the sweet spot for real subsonic, not transonic where you still get an increase in sound signature. Our 4 inch barrel still keeps factory 147's subsonic. A 5 inch barrel is too long to keep a good subsonic sound signature.
http://www.ballisticsbytheinch.com/gifs/9federal147hs.gif
147gr HST stays subsonic out of my 5" TROS.
One of my favorite SD loads for my AR9mm is 147gr XTP over 6.5gr of 3N38 for 1,180fps from my 5" TROS!
147gr HST stays subsonic out of my 5" TROS.
One of my favorite SD loads for my AR9mm is 147gr XTP over 6.5gr of 3N38 for 1,180fps from my 5" TROS!
1,180fps is transonic. You will notice a significant drop in sound signature when you are around 950fps.
http://en.wikipedia.org/wiki/Transonic
"Transonic is an aeronautics term referring to the condition in which a range of velocities of airflow exist surrounding and flowing past an air vehicle or an airfoil. Air flow velocities are concurrently below, at, and above the speed of sound at the pressure and temperature of the airflow of the air vehicle's local environment (about mach 0.8–1.2). It is formally defined as the range of speeds between the critical mach number, when some parts of the airflow over an air vehicle or air foil are supersonic, and a higher speed, typically near Mach 1.2, when all of the airflow is supersonic. Between these speeds some of the airflow is supersonic, and some is not."
1,180fps is transonic. You will notice a significant drop in sound signature when you are around 950fps.
http://en.wikipedia.org/wiki/Transonic
"Transonic is an aeronautics term referring to the condition in which a range of velocities of airflow exist surrounding and flowing past an air vehicle or an airfoil. Air flow velocities are concurrently below, at, and above the speed of sound at the pressure and temperature of the airflow of the air vehicle's local environment (about mach 0.8–1.2). It is formally defined as the range of speeds between the critical mach number, when some parts of the airflow over an air vehicle or air foil are supersonic, and a higher speed, typically near Mach 1.2, when all of the airflow is supersonic. Between these speeds some of the airflow is supersonic, and some is not."
Yes I knew that, sorry I wasn't clear but I wasn't saying that particular load was subsonic or quiet cause it's far from it....it makes a nice SD load though :) I do try to keep my Subsonic loads around 950fps.
Gotcha, sorry about that.
Interesting chart DDLES. Looks like no real velocity benefit to barrels longer than about 5" with that particular load, and as you said after about 4" there may be louder sound.
You said you're doing 4" barrels? Is that a 4" threaded barrel? I have a YHM 9mm can that mounts to a flash hider.
Interesting chart DDLES. Looks like no real velocity benefit to barrels longer than about 5" with that particular load, and as you said after about 4" there may be louder sound.
You said you're doing 4" barrels? Is that a 4" threaded barrel? I have a YHM 9mm can that mounts to a flash hider.
Yep, threaded 1/2X28
I had no problem keeping reloads subsonic out of my colt 10.5" upper. ;)
Reloading is the way to go. 147gr. rainier bullets and iirc, 4.3 grains of red dot...
If you reload with a slow burning powder like HS-6 or Power Pistol, you can get a 115 grainer up in the 1500 + fps range for 75-100 yard shots.
With quality 115 or 124 grain ammo, you should get a 16" barrel.
Find some GECO or MFS South African 115 grain ammo - nice and hot and will shot long accurately.
If you use PMC or some other crappy ammo, you should still be getting another 75-100 fps with the longer barrel.
45ACP does not accelerate much after 10.5". That is why 45ACP is best suited for AR-15 pistols - 9-10" barrels. Having ADCO cut mine down soon:D
I fire a lot of suppressed 9mm - been making my own ammo for quite a while now - 147gr and 4.8gr Unique powder. More or less tailored for me to works well suppressed barrels up to 10.5"
LonghunterCO
03-25-10, 22:17
I had read that the Uzi was built around the 10" barrel because anything longer than that, the bullet actually started slowing down...looking at the cart that doesn't seem to be the case.
Gents,
Seeing as you have a 9mm barrel thread going, I've got a couple of questions maybe someone can answer. I want to build a retro looking 635 upper.
1. Were the original Colt 635's produced with a 10.5" barrel?
2. Most barrels I've found come 1-10" twist except model 1 sales which is 1-15", is there any real issue with the slower twist?
3. If someone has a close up pic of the flash hider/bayonet lug from original 635 upper I sure would love to see one.
My issue is that the barrels by Spikes and RRA look slightly longer than the original Colt barrel to me. The distance between the flash hider and bayonet lug looks longer. Model 1 sales cuts their barrel to 10.25". I like the look of the flash hider almost touching the bayonet lug. However, spending extra money to cut 1/4inch is not in the budget right now. Thanks for the help.
Necroposting this thread up from the deep. Some of the info is old and new manufacturers have started making 9mm AR barrels. And I don't think my questions warrant a new thread.
I have a AR-9 lower inbound for a SBR build. I'm trying to decide on barrel length and also which manufacturer to go with. My plan is a 3.5-5.5" barrel in a 7-9" rail with my Octane 9 inset into the rail atleast half of the can's length. My goal with the planned upper is suppression. I was first contemplating buying a Colt SMG barrel and having it cut down and threaded by ADCO. Then I noticed Ballistic Advantage makes 9mm barrels and they are on sale right now. Buying on of those would be cheaper than going with the Colt barrel and having it cut, and cheaper than most other makers also. They seem to have a good reputation but they only offer a 5.5" barrel. I have looked at ADCO's barrels but I think they are priced close to the price of the Colt. This will be my first 9mm AR and first full build so any info or tips or guidance is appreciated.
I would think gtg. They make aero precision barrels. If you do buy make sure to use headspace gages to be sure
Sent from my SM-G900P using Tapatalk
Try this site:
http://www.ballisticsbytheinch.com/9mmluger.html
Looks to me like 12 inches is where the curve flattens out for most types of 9mm ammo.
Link was old ... here is the latest to 9mm ballistics:
http://www.ballisticsbytheinch.com/9luger.html
Link was old ... here is the latest to 9mm ballistics:
http://www.ballisticsbytheinch.com/9luger.html
Thanks. From what I've read and heard 950 is the "magic number" for suppression. I wish more people made 4.5" barrels.
Anything under 1050fps and you should be good. All of your 147+gr is great and hand loaded 124gr and 135gr is good. I like 5.5" for 9mm.
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I am going with the Ballistic Advantage 5.5" with a 10" ALG rail. They were having a sale on those barrels last week so I grabbed one.
Anything under 1050fps and you should be good. All of your 147+gr is great and handle a dedicated 124gr and 135gr is good. I like 5.5" for 9mm.
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I have one 5.5 BA barrel and 8.3 one been good for me so far well over 2 k shoot from them. I shoot with 45 cal suppressor and with 158 gn subs no problems other than finding more of it.
moriartiarmaments
06-17-17, 09:30
16" 4150 CMV STEEL M4 CONTOUR BARREL FOR 9MM AR
Thanks. From what I've read and heard 950 is the "magic number" for suppression. I wish more people made 4.5" barrels.
Faxon makes a 4.5" now and they have a 9mm proprietary BCG as well.
FaxonNathan
06-21-17, 09:39
Faxon makes a 4.5" now and they have a 9mm proprietary BCG as well.
Just to clarify - its not proprietary to our barrel. It should work with any barrel and lower out there!
ffhounddog
06-22-17, 04:13
I have a 5.5 AR-9. I have thought about adding an 7.5 or a 8 inch.
Just to clarify - its not proprietary to our barrel. It should work with any barrel and lower out there!
Yea I said proprietary and the correct word would have been "dedicated" 9mm BCG. Hoping to build one using both of those products from you all soon!
samuelcruz
08-01-17, 08:42
5" is what I found to be the optimal length. I like the 5" barrel a lot.
I fire a lot of suppressed 9mm - been making my own ammo for quite a while now - 147gr and 4.8gr Unique powder. More or less tailored for me to works well suppressed barrels up to 10.5"
Gawd that must be a 'dirty' load in blowback operation!
I LOVE Unique for reloading reduced 44 Mag loads to 44 Special level - awesome at bowling pin (big pin) shoots - even awesome for reduced rifle loads using cast boolits - but ahhh so dirty!
5" is what I found to be the optimal length. I like the 5" barrel a lot.
Can you expand on this? Why 5"?
I like 5" as well. Most people with an AR9 want it because they want to suppress it. 5" gives solid ballistics and any longer just makes it longer
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TomMontana
08-09-17, 16:32
4.5" for suppressed. If not suppressed, then the 5.5" allows you to use a flash can with fore ends in the 7" range and have part of the can sticking out which is more aesthetically pleasing to me. The 8.5" allows you to add a brake with fore ends in the 9" range. Anything longer than 8.5" kinda defeats the SBR benefits on a 9mm. Also, the Faxon barrels are very nice. Most other 9mm barrels are of the gov't style thicker heavier barrels.
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