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Posted: 3/14/2002 7:39:34 PM EDT
What's the muzzle velocity of a .308 fired from a 16" barrel such as that on the AR10 carbines?
Link Posted: 3/15/2002 9:26:58 AM EDT
btt
Link Posted: 3/15/2002 3:50:12 PM EDT
I find it hard to believe that no one here has fired a 16" AR10 through a chronograph.
Link Posted: 3/15/2002 4:55:33 PM EDT
[Last Edit: 3/15/2002 5:14:49 PM EDT by Arock]
Well read this www.tacticaloperations.com/SWATbarrel/ they say MV for a .308 is not much lower with a 16" barrel than with a longer barrel. Has to do with expansion ratios of the cartridge or the amount of powder versus the swept area of the barrel.





Link Posted: 3/15/2002 5:06:18 PM EDT

Originally Posted By Arock:

Has to do with expansion ratios of the cartridge or the amount of powder versus the swept area of the barrel.



Say WHAT ??
Link Posted: 3/15/2002 5:18:09 PM EDT

Originally Posted By 5subslr5:

Originally Posted By Arock:

Has to do with expansion ratios of the cartridge or the amount of powder versus the swept area of the barrel.



Say WHAT ??



It is the ratio of case volume to barrel volume. You stupid looser.
Link Posted: 3/15/2002 5:20:58 PM EDT

Originally Posted By 5subslr5:

Originally Posted By Arock:

Has to do with expansion ratios of the cartridge or the amount of powder versus the swept area of the barrel.



Say WHAT ??



Hi guy, how's Oklahoma today? What I've read about expansion ratio could fill a short paragraph. My understanding comes from the linked article and a couple more from the same publication. Basically I understand it as the amount of barrel volume required to burn a given amount of gunpowder. Don't know if a standard burn rate is applied. It may not give an absolute value but a relative one instead. Glance over that article and see what you think.
Link Posted: 3/15/2002 5:22:26 PM EDT
Hey nekkid, back off...5subslr5 is a friend engaged in a friendly question.
Link Posted: 3/15/2002 5:42:13 PM EDT

Originally Posted By Arock:
Hey nekkid, back off...5subslr5 is a friend engaged in a friendly question.



=me, tech weenie, dork, looser, moron, stupid. 10-4? Roger That? over.

This usually denotes a good natured conversation will take place.

Yes, I know that Loser is mispelled.

chill.
Link Posted: 3/15/2002 5:45:48 PM EDT

Originally Posted By Arock:

Originally Posted By 5subslr5:

Originally Posted By Arock:

Has to do with expansion ratios of the cartridge or the amount of powder versus the swept area of the barrel.



Say WHAT ??



Basically I understand it as the amount of barrel volume required to burn a given amount of gunpowder. Don't know if a standard burn rate is applied. It may not give an absolute value but a relative one instead. Glance over that article and see what you think.



Arock,
I believe you've posted this article once before as I have it bookmarked.

I've read it before and just read it again.

As an aside I've decided to get my ArmaLite AR-30 in .300 WinMag. This article even gives some information regarding that caliber and barrel length.

Your "barrel volume" makes sense. I didn't remember seeing the term "swept area" used before and didn't know the definition.

I like the approach the SWAT boys took. Shoot, measure, chop - shoot, measure, chop.
Link Posted: 3/15/2002 5:47:46 PM EDT

Originally Posted By Nekkid80:

Originally Posted By Arock:
Hey nekkid, back off...5subslr5 is a friend engaged in a friendly question.



=me, tech weenie, dork, looser, moron, stupid. 10-4? Roger That? over.

This usually denotes a good natured conversation will take place.

Yes, I know that Loser is mispelled.

chill.



Still, thanks very much for the clarification !
Link Posted: 3/15/2002 10:07:57 PM EDT
Thank you VERY much for the article!!!

That was a cool experiment.

20" allows for max velocity. 36 FPS loss when going from 20" to 18". I wonder how much loss for the next two inches? Too bad they didn't continue to chop down the barrel. I would think that the next two inches would be more than 36 FPS loss, but how much?

I would still appreciate it if anyone has chonographed 308 out of a 16" barrel.
Link Posted: 3/15/2002 11:47:23 PM EDT
Go to www.falfiles.com and do some research. 16" FAL carbines are very popular with the guys. They seem to think you need a 17" barrel to get a full powder burn and as a result, the shorter barrel produces a lot of muzzle flash. Anyway, no one seems to complain about the loss of muzzle velocity with the 16" barrel.
Link Posted: 3/16/2002 6:01:12 AM EDT
Q-Man,

www.shooterready.com/ar10.html

Go ask SW. He has a great load for his 16"ers that are 1/5 MOA @ 800yds.

Dave S

Link Posted: 3/16/2002 7:45:58 AM EDT

Originally Posted By DaveS:
Q-Man,

www.shooterready.com/ar10.html

Go ask SW. He has a great load for his 16"ers that are 1/5 MOA @ 800yds.

Dave S




Dave,
thanks for this link. Had not heard of this guy before.
Link Posted: 3/16/2002 7:49:07 AM EDT

Originally Posted By Q-Man:
I find it hard to believe that no one here has fired a 16" AR10 through a chronograph.



Q-Man, I know one person that will almost certainly have this information and have emailed today.

However, it is likely to be Monday before I have a response.
Link Posted: 3/16/2002 8:20:58 AM EDT

Originally Posted By 5subslr5:

Originally Posted By Q-Man:
I find it hard to believe that no one here has fired a 16" AR10 through a chronograph.



Q-Man, I know one person that will almost certainly have this information and have emailed today.

However, it is likely to be Monday before I have a response.



I did receive a reply to my email this AM but this person also does not have the information.

Back to square one.
Link Posted: 3/16/2002 12:23:53 PM EDT
The average velocity out of my 16" AR10 was 2609 fps with Hirtenburg surplus. That's 15 feet from the muzzle.
By contrast, my 21" FAL shoots the same ammo at 2694 fps.
Link Posted: 3/16/2002 1:32:07 PM EDT

Originally Posted By Garmentless:
The average velocity out of my 16" AR10 was 2609 fps with Hirtenburg surplus. That's 15 feet from the muzzle.
By contrast, my 21" FAL shoots the same ammo at 2694 fps.



Garmentless,
you shooting a '10A4 carbine or AR-10(TC). I know it shouldn't matter for mv but just curious.

THANKS for some good info !
Link Posted: 3/17/2002 7:47:37 PM EDT
Thanks for the good info.

It seems like such a little difference between the 16" and 20+", so why even bother having barrels beyond 16"?
Link Posted: 3/17/2002 8:36:08 PM EDT
In chronograph testing, I used a 21" and an 18" FAL. With RG and DAG surplus ammo, the velocity drop was approx. 50 fps (2772 vs. 2721). Others on the FAL forum reported a velocity loss of between 160 fps and 195 fps when shortening their barrels from 21" to 16.5". So while shortening the barrel by three inches yielded very little velocity loss, removing another 1.5" seems to have a much greater impact.

The only other short barrel I've personally seen tested was another shortened FAL kit gun. This was a friend's 14.5" (plus 2" muzzle brake) barrelled rifle. That really short barrel didn't quite break 2500 fps with various surplus 7.62 loads.
Link Posted: 3/18/2002 1:21:10 PM EDT
5sub,
That's an A4.
Q-Man, remember, that's only one make of ammo. As Wadman points out, some people are getting more than double that loss. I believe that as you get heavier bullets/slower powder, the velovity loss would probably be greater. The surplus I was using was 147gr.
Also, the muzzle blast with a 16" is mighty wicked especially with the Armalite Noise Enhancer on the end.
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