Muzzle Velocity: 16" vs 20" in 223


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Tarvis
March 31, 2008, 10:59 PM
What kind of losses can I expect going from a 20" to a 16"? Im planning on loading 55gr vmax's pushed by win 748. The good book says 2900 fps from a 20" barrel at max load from whatever rifle they shot it out of, but I'm considering the shorter barrel for a lighter setup at the cost of MV.

Any ideas on how much MV I can expect would be great. FWIW, the rifle in question is a home built ar15.

Thanks

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rg1
April 1, 2008, 04:26 AM
Approx 90-125 fps depending on the gun would be my estimate.

moosehunt
April 2, 2008, 01:10 AM
Pretty well acepted that you will loose 100 to 150 FPS per inch. If you're lucky, maybeso only 75 FPS per inch. As the barrel gets shorter, the effect gets lesser, but you're likely looking at 100 FPS per inch.

Bullet
April 2, 2008, 01:37 AM
You might look here -

http://www.ar15.com/content/page.html?id=213


.

Tarvis
April 2, 2008, 01:42 AM
Pretty well acepted that you will loose 100 to 150 FPS per inch.
I have heard that before, but I posted the same question on the rifle country section and everybody seems to concur on 100 or so fps gong from 20" to 16" on an AR, including Bullet's link.

steve4102
April 2, 2008, 04:33 AM
According to this test you will lose about 175fps from a 20-16 inch barrel. That comes to roughly 44fps/inch.
http://www.accuratereloading.com/223sb.html

According to QL with a 50gr Hornady you will lose 178fps or 44.5fps/inch.

dagger dog
April 2, 2008, 07:43 PM
Standard guidelines on approximate velocity changes for each 1" change in barrel length. Based on 20" to 26" barrel.
muzzle velocity up to 2,000fps change expected, about 5fps
"" "" " " 2,001fps-2,500fps "" , about 10fps
"" "" "" 2,501fps-3,000fps "" "" , about 20fps
""" """ """ 3,001fps-3,500fps "" "" ,about 30fps
""" "" "" 3,501fps-4,000fps "" "" ,about 40fps

The word used above , APPROXIMATE , is important. This is a general guide based upon a veriety of firearms and calibers all averaged together.


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rcmodel
April 3, 2008, 01:00 PM
That's pretty close to exactly right.

I found a load test in the "Book of the AR-15" that tested 24 different 55 grain factory loads in different length AR's.

The average velocity loss between a 20" and 16" barrel was 92 FPS, or 23 FPS per inch.

Slower loads then the .223 use faster powder as a general rule.

The Big fast Magelums use much slower powder then the .223.

So, velocity loss is less with the slow ones then the very fast ones.

The .223 fits nicely right in the middle.

rcmodel

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