9mm SBR: 5" v. 9.5" v. 10.5"

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[ARCHIVED THREAD] - 9mm SBR: 5" v. 9.5" v. 10.5"

Posted: 12/16/2005 4:21:39 AM EDT

Does anyone have stats on velocity of 9mm from 5", 9.5", and 10.5" AR barrels?

Posted: 12/16/2005 4:41:25 AM EDT

[#1]

Sorry that I don’t have exact info, but if memory serves me correctly a 9.5 to 10.5 barrel length is the optimal length for max velocity. Anything longer you lose velocity due to barrel friction, anything shorter you don’t get full potential out of the powder burn!
I am trying to save up so that I can get my 16 inch cut down to 10.5 and add a 5.5 brake to make it legal.

Hope that helps...

P.S. I once found a link on ARFCOM about a study done on this topic with velocity charts that supported this info, maybe some one still remembers where that info is?

Posted: 12/16/2005 9:16:58 PM EDT

[#2]

Humm.. I thought a 10.5" barrel would shoot most standard ammo at SUBSONIC speeds. I think optimal barrel length for full powder burn is a bit longer. ???

Posted: 12/17/2005 3:52:18 AM EDT

[#3]

Quoted:
Humm.. I thought a 10.5" barrel would shoot most standard ammo at SUBSONIC speeds. I think optimal barrel length for full powder burn is a bit longer. ???

I'm afraid not. Most (115 and 126 grain) 9mm is supersonic from even a 4 inch barrel.

Posted: 12/17/2005 4:20:07 AM EDT

[#4]

Quoted:
Humm.. I thought a 10.5" barrel would shoot most standard ammo at SUBSONIC speeds. I think optimal barrel length for full powder burn is a bit longer. ???

I don’t want to disagree with any one since I do not have the facts and figures on hand, but the article that was posted was very clear in what they found and had the velocity charts to back it up!
I will admit it sounded weird to me also, but when you crono the stuff repeatedly from the same test rigs with the same ammo it is hard to refute.

I wish I could find the link to the damn posting!
It was very informative and had a lot of charts with tons of pictures!
Any help finding that review would be great!

Posted: 12/17/2005 9:18:38 AM EDT

[#5]

Just another idea i cut my RRA 9mm barrel to 15" and installed a Bushmaster 5" slipover flashhider and pinned and welded it. It looks like a 11.5" barrel and you still get a 15" barrel. Email me for pics
Thanks MGP

Posted: 12/17/2005 4:20:01 PM EDT

[#6]

On occasion el-cheapo American Eagle 147gr will leave my 10.5" 9mm at supersonic velocities. Easy to tell the difference with the can on.

Here is a link to one of the 9mm velocity tests: Velocity Tests

Posted: 12/17/2005 6:48:05 PM EDT

[#7]

Quoted:
Just another idea i cut my RRA 9mm barrel to 15" and installed a Bushmaster 5" slipover flashhider and pinned and welded it. It looks like a 11.5" barrel and you still get a 15" barrel. Email me for pics
Thanks MGP

And it is now heavier. I am not sure what you gained here.

Bob

Posted: 12/17/2005 8:48:48 PM EDT

[#8]

Quoted:
Quoted:
Just another idea i cut my RRA 9mm barrel to 15" and installed a Bushmaster 5" slipover flashhider and pinned and welded it. It looks like a 11.5" barrel and you still get a 15" barrel. Email me for pics
Thanks MGP

And it is now heavier. I am not sure what you gained here.

Bob

You get the shorty look with higher velocity and its not that heavy Thanks MGP

Posted: 12/18/2005 4:42:46 AM EDT

[#9]

I remember an article where they took a 16" or longer (I am not sure) barrel and cut one inch off at a time to see what velocity changes were observed. Anyone ever read this or a similar article? While the one mentioned above compared the pistol vs. rifle barrel length fairly well, I would like to see the inch by inch comparison.

Bob

Posted: 12/18/2005 10:19:17 AM EDT

[#10]

Quoted:
I remember an article where they took a 16" or longer (I am not sure) barrel and cut one inch off at a time to see what velocity changes were observed. Anyone ever read this or a similar article? While the one mentioned above compared the pistol vs. rifle barrel length fairly well, I would like to see the inch by inch comparison.

Bob

I tested a 9mm AR15 with a 9" barrel with winchester white box and got 1268fps i have to test this one with a 15" barrel

Posted: 12/18/2005 10:23:48 AM EDT

[#11]

Quoted:
Quoted:
I remember an article where they took a 16" or longer (I am not sure) barrel and cut one inch off at a time to see what velocity changes were observed. Anyone ever read this or a similar article? While the one mentioned above compared the pistol vs. rifle barrel length fairly well, I would like to see the inch by inch comparison.

Bob

I tested a 9mm AR15 with a 9" barrel with Winchester white box and got 1268fps i have to test this one with a 15" barrel

I have an un-assembled 10.5" that is waiting for the Form 4 to clear that I will try later this month or next and will post results as well. Maybe we can start our own chart using WWB as the standard load for comparison purposes.

Bob

Posted: 12/18/2005 10:28:07 AM EDT

[#12]

Quoted:
Quoted:
Quoted:
I remember an article where they took a 16" or longer (I am not sure) barrel and cut one inch off at a time to see what velocity changes were observed. Anyone ever read this or a similar article? While the one mentioned above compared the pistol vs. rifle barrel length fairly well, I would like to see the inch by inch comparison.

Bob

I tested a 9mm AR15 with a 9" barrel with Winchester white box and got 1268fps i have to test this one with a 15" barrel

I have an un-assembled 10.5" that is waiting for the Form 4 to clear that I will try later this month or next and will post results as well. Maybe we can start our own chart using WWB as the standard load for comparison purposes.

Bob

Sounds Good

[ARCHIVED THREAD] - 9mm SBR: 5" v. 9.5" v. 10.5"

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