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Avg velocity vs bbl lenght .308

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Avg velocity vs bbl lenght .308 was created by OleCowboy

Found this:

Industry standard barrel lengths and average velocities

Bullet weight 20” Tactical - 22” Sporter - 24” M24 Sniper - 26”
125-130...................3000 ........3050 ........3100 .......3150
144-150 .................2800 .........2850 .........2900 ........2950
155 ....................... .2750 ..........2800 ..........2850 ...........2900
165-168 ..................2650 ...........2700 ........2750 ..........2800
178-180 ..................2500 ...........2550 .........2600 .........2650
200 ........................2300 .............2350 ..........2400 ..........2450

Looking at the chart, every 2 in of bbl length costs/gives 50 fps in velocity (assuming a linear progression, which it certainly appears to be)
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Last edit: 10 years 10 months ago by OleCowboy.
10 years 10 months ago #25722

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Replied by magi on topic Avg velocity vs bbl lenght .308

It's is interesting..... I'm going to have to look up charts for my 16 in barrel.....
10 years 10 months ago #25727

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Replied by Lizardette on topic SOC's AR10-TU Magnum 300 RSAUM

Interesting.

I'm guessing that they used cartridges with the same powder for a given bullet weight regardless of barrel length. What I'd be even more interested in is velocity gains in a longer barrel using progressively slower burning propellents.

The way I always heard it, you can get more velocity with a given bullet weight out of a longer barrel by using slower burning propellents. I'm not sure if it's true or not (I'm leaning toward not) but I'd be interested in seeing some actual data on the subject.
10 years 10 months ago #25793

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Replied by OleCowboy on topic Avg velocity vs bbl lenght .308

What I found interesting was the linear differences, Always +/- 50 fps regardless of bullet weight or bbl length. This is a good span of length from 20" - 26".

This is good info for a couple of reasons:

1) No matter the bbl length the reality is that it makes little difference even if you begin to extrapolate. In order to see a 10% impact you need to increase/decrease bbl length by 10 in! That would be a 32 in bbl if you base it 22 in.

My guess is somewhere you hit diminishing returns, just not sure where.

2) Overall my impression is that bbl length is importance is more tied to the distance you are shooting at than anything else. In my 150 yd world build around pie plate accuracy whether I us a 18" or a 28" bbl is not really a big deal. As your needs out beyond 300 yds grow bbl length begins to become a key factor and if you are a sniper then it becomes all important.

3) If you are in a build then this could be very helpful. You can take the .308 and extend its effective range from about 800 yds to out to about 1000 yds but by giving your self more bbl length. KInda cool if you ask me...
10 years 10 months ago #25803

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Replied by magi on topic Avg velocity vs bbl lenght .308

This was interesting..... As I have a 16 and 20 incher....... And I believe this is one of the two rounds I'm using for now.......



I certainly believe that given the same bullet.... That using powders to tune performance would make some deference.......
Last edit: 10 years 10 months ago by magi.
10 years 10 months ago #25806

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Replied by OleCowboy on topic Avg velocity vs bbl lenght .308

No matter how you view the chart the different in fps is only about 300 fps
10 years 10 months ago #25810

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Replied by Lizardette on topic Avg velocity vs bbl lenght .308

The one thing that I've heard barrel length makes a big difference in is accuracy with iron sights. Even that might not be true at short ranges. Then again, I imagine that there's a reason International Palma shooters seem to favor 30 inch barrels.

Bullet weight and shape probably have a lot more impact at longer ranges versus starting velocity.
10 years 10 months ago #25814

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Replied by magi on topic Avg velocity vs bbl lenght .308

I thought this to be an interesting article dealing with this subject...

BARREL LENGTH AND THE PRECISION RIFLE
Why shorter barrels may often be better
by
Eugene Nielsen

www.tacticaloperations.com/SWATbarrel/
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10 years 10 months ago #25845

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Replied by 13fcolt on topic Avg velocity vs bbl lenght .308

I simplify it down to harmonics vs distance. Shorter barrels are stiffer and I would expect, all other things being equal, a shorter barrel to do measurably better than a longer one. Right up until you hit the transonic drop in velocity.
One thing that negates this improvement is that shorter barrels tend to have smaller profiles, reducing the rigidity.

Technology is improving, and barrels are getting shorter as things get better. Berger makes a bullet now, with a new base design, that they claim remains stable through transonic flight, potentially improving the long distance reach with less barrel. It's just so dang expensive.

I am hopeful that I will see the consistently 1000m capable carbine in my lifetime.
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10 years 10 months ago #25847

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Replied by magi on topic Avg velocity vs bbl lenght .308

This was a very interesting discussion on performance and barrel length for the 308...

thefiringline.com/forums/archive/index.php?t-388353.html
10 years 10 months ago #25880

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