16 vs 18 in barrel..

[Boris B]

So, I am wondering what everyone thinks are the pros/cons of one over the other... or simply if anyone has a personal preference for whatever reason...

Be interested to hear what you think... And I am only asking so I can learn from you're input...

If you were buying a new AR, and had that choice, which would it be...

A 16 or 18 inch barrel.. and why...

and before you ask the obvious....it depends what you are using it for question.. stop... we can cross that bridge later..

Lets hear pros/cons if there are any to hear..

[Boris B]

OK so so far in my research I am seeing that maybe one of the largest aspects is a 18 inch barrel CAN use a Rifle length gas system which can affect the operating of the rifle...

Differences in velocity, accuracy, range are not so much a big deal...

[cyphertext]

I'm no expert, but I wouldn't expect a drastic difference between 16" and 18". Now, if you widened your scale from say 14.5" all the way out to 20"+ you would see some differences along the way.

[Boris B]

Originally Posted by cyphertext

I'm no expert, but I wouldn't expect a drastic difference between 16" and 18". Now, if you widened your scale from say 14.5" all the way out to 20"+ you would see some differences along the way.

Yeah I think you are right, that's pretty much what I'm reading in other places...

There is some really good info out there on the subject...

A thread titled , "18 inch or 16 inch barrel" , at M4Carbine has some good stuff.. worth a read...

[rojodiablo]

Originally Posted by Boris B

So, I am wondering what everyone thinks are the pros/cons of one over the other... or simply if anyone has a personal preference for whatever reason...

Be interested to hear what you think... And I am only asking so I can learn from you're input...

If you were buying a new AR, and had that choice, which would it be...

A 16 or 18 inch barrel.. and why...

and before you ask the obvious....it depends what you are using it for question.. stop... we can cross that bridge later..

Lets hear pros/cons if there are any to hear..

1. For sight picture with open sights and not a scope? 18" bbl with a midlength or rifle length gas system will give a better sight picture.
2. For absolute performance? The extra 2" of barrel give a few more FPS because of the increased pressure developed/ less gas pressure vented out the barrel unburned.
3. For those looking for maximum muzzle flash reduction; the longer the barrel, the more complete the combustion, and the less muzzle flash. (It means a lot if you hunt at night. First pull, the blast blinds you.) A true flash hider works better on the 18".
4. Overall maximum accuracy. Nobody........ and I mean NOBODY is competing in the Presidents' Challenge with an AR with a 16" barrel. No one. There is a reason for that. No one..... NO ONE is competing at 1,000 match shooting with a 16" barrel. There is a reason for that. (At 1K, they are pretty much 100% using optics, so sight picture is a non issue.)
5. Carry ability; The 16 IS better than the 18. Especially if you would expect to swing the rifle a lot, or climb in and out of a vehicle with said rifle in a hurry.
I wish I had the option for a Sport barrel from the factory in 18"- I would have paid extra for that.

[Drag]

Barrel Length Studies in 5.56mm NATO Weapons

The M855 ammunition is optimized for a 20-inch barrel with a 1:7 twist barrel.  It was not surprising that the greatest velocity of 2,979 ft/sec was obtained in the 20-inch barrel, and the lower velocity on barrels greater than 20 inches is explained by decreased pressure driving the bullet no longer exceeding the slowing from friction.  After all, Eugene Stoner designed the cartridge for the 20 inch barrel.

To answer your specific question, "If you were buying a new AR, and had that choice, which would it be...A 16 or 18 inch barrel.. and why"... I would get an 18" barrel because my next build will be SPResque, and I already have two 16 inch uppers. Though, ideally I would get a 20 inch barrel because that length has been proven to extract the most energy out of the M855 round.

[oneyeopn]

The one thing I have found in my studying over barrel length was that 100% powder burn happens at around 18". If I had the option of picking up a Sporting rifle and my choices were 16" and 18" I would take the 18 just because of that fact and the extra 100fps with no additional powder. In fact I could reduce the charge and stay at my present velocities.