Avg velocity vs bbl lenght .308

More
11 years 5 months ago - 11 years 5 months ago #25722 by OleCowboy
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)
Last edit: 11 years 5 months ago by OleCowboy.
The following user(s) said Thank You: Lizardette

Please Log in or Create an account to join the conversation.

More
11 years 5 months ago #25727 by magi
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.....

Please Log in or Create an account to join the conversation.

More
11 years 5 months ago #25793 by Lizardette
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.

Please Log in or Create an account to join the conversation.

More
11 years 5 months ago #25803 by OleCowboy
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...

Please Log in or Create an account to join the conversation.

More
11 years 5 months ago - 11 years 5 months ago #25806 by magi
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.......

This image is hidden for guests.
Please log in or register to see it.


I certainly believe that given the same bullet.... That using powders to tune performance would make some deference.......
Last edit: 11 years 5 months ago by magi.

Please Log in or Create an account to join the conversation.

More
11 years 5 months ago #25810 by OleCowboy
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

Please Log in or Create an account to join the conversation.

More
11 years 5 months ago #25814 by Lizardette
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.

Please Log in or Create an account to join the conversation.

More
11 years 5 months ago #25845 by magi
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/
The following user(s) said Thank You: jtallen83

Please Log in or Create an account to join the conversation.

More
11 years 5 months ago #25847 by 13fcolt
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.

Please Log in or Create an account to join the conversation.

More
11 years 5 months ago #25880 by magi
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

Please Log in or Create an account to join the conversation.