.308 barrel length for Max Velocity?

Raider556

Raider556

CGN Regular
Rating - 100%
94   0   0
Location
Regina, SK
Ok, so .308 velocity is talked about a lot.:redface: But I can't seem to find much velocity data on people going past 30" barrels.

While I know the gains going crazy long on a barrel do not gather huge returns... I am very curious what the barrel length would be to achieve the greatest velocity possible?:confused:

At some point in barrel length you start to lose velocity. Is that 40"? 50"? 70"?

Of course bullet and load will vary with any test. But some insight into this would be much appreciated!;)
 
Out to 28" velocity still increases with more barrel length. Where the peak occurs isn't clear and I think would vary considerably depending on your bullet weight and powder burn rate (heavier, slower benefiting from more barrel length). This seems to be reflected in the data in the link (see data for 168 and 180 grain ammo) even though the powder isn't specified (commercial ammo).

See the link below and note that 147 and 150 grain ammo shows diminishing returns after about 26".

http://rifleshooter.com/2014/12/308...ato-barrel-length-versus-velocity-28-to-16-5/
 
Good stuff.

As we can see, there is still gains to be had at 28". Diminishing return aside... ;)

How long till you actually start losing velocity?:confused:
 
This one of mine is 28" plus the brake.

0oy46o5h.jpg


I've never crono'd it, but speeds are pretty stout according to backwards application of data with iSnipe.
 
Well a 22lr doesn't start to lose velocity until somewhere around 16 inches... considering how little powder that has, I doubt you could really get a barrel long enough. Sure, there must be a certain length that would lead to decreased velocity but it is probably longer than anyone would ever bother with...
 
Raider556 said:
Ok, so .308 velocity is talked about a lot.:redface: But I can't seem to find much velocity data on people going past 30" barrels.

While I know the gains going crazy long on a barrel do not gather huge returns... I am very curious what the barrel length would be to achieve the greatest velocity possible?:confused:

At some point in barrel length you start to lose velocity. Is that 40"? 50"? 70"?

Of course bullet and load will vary with any test. But some insight into this would be much appreciated!;)
Click to expand...

You will need pressure trace equipment to answer you question.

Different powders and operating parameters ie bullet, will change the result.

I use a 30" barrel. I know of those going out to 34"... did it help????

No clue.

Jerry
 
Suther said:
Well a 22lr doesn't start to lose velocity until somewhere around 16 inches... considering how little powder that has, I doubt you could really get a barrel long enough. Sure, there must be a certain length that would lead to decreased velocity but it is probably longer than anyone would ever bother with...
Click to expand...

But inquiring minds have to know!!!:slap::d
 
Raider556 said:
Good stuff.

As we can see, there is still gains to be had at 28". Diminishing return aside... ;)

How long till you actually start losing velocity?:confused:
Click to expand...

If you are trying to optimize for long range accuracy, trying to maximize velocity may actually be counterproductive since you lose barrel stiffness with length (for a given barrel diameter and weight). Once the bullet is still stable at the max. distance at which you are shooting I'd think that other factors would be more important.

If you look at the data in the link, the SD of the velocity measurements is greater than the measured change per inch of barrel length. This could mean that the for a specific type of ammo, powder load, bullet weight, etc. could be having as much or more influence on velocity than the barrel length.

Think about getting a long barrel...say 36" which you are convinced is at or past the optimal length, and then found that the load that shot best with your chosen bullet was at near-minimum load.
 
Pr589 said:
If you are trying to optimize for long range accuracy, trying to maximize velocity may actually be counterproductive since you lose barrel stiffness with length (for a given barrel diameter and weight). Once the bullet is still stable at the max. distance at which you are shooting I'd think that other factors would be more important.

If you look at the data in the link, the SD of the velocity measurements is greater than the measured change per inch of barrel length. This could mean that the for a specific type of ammo, powder load, bullet weight, etc. could be having as much or more influence on velocity than the barrel length.

Think about getting a long barrel...say 36" which you are convinced is at or past the optimal length, and then found that the load that shot best with your chosen bullet was at near-minimum load.
Click to expand...


This. If you only want to look at velocity, Each in beyond 24-26 depending on the cartridge starts getting diminishing returns for each added inch and no one was testing beyond 34" or so.
If you want to look at accuracy and precision & velocity, each added inch reduces barrel stiffness thus making barrel harmonics and tuning more difficult as the sweet spot gets smaller. So to counteract your added barrel length you need a thicker barrel. SO when you ask how long can/should a barrel be, the answer depends on how thick a barrel can your action take and how heavy do you want your rifle to be. Longer = fatter = heavier

The barrel makers sites do a good job of discussing these topics but here is one I especially liked.

http://rifleshooter.com/2014/12/308...ato-barrel-length-versus-velocity-28-to-16-5/
 
308 Winchester Barrel length in inches versus Muzzle velocity in feet-per-second (ft/sec) credit to : Rifleshooter.com
Barrel length InchesWinchester 147gr. FMJIMI Samson 7.62 150gr. FMJFederal 168gr. Gold MedalWinchester 180gr. PP
282965282327062632
272962280026972607
262955280126732597
252917276926592585
242909276626352553
232877274426182553
222837271825972527
212807268325802507
202804267925652478
192757263425322441
182739259525232411
172707257724812401
16.52682256124662373
AVG velocity loss fps/inch24.622.820.922.5
 
here is some more data

http://www.6mmbr.com/308win.html

Emil Praslick says: December 16, 2015 at 12:14 pm

I had a 34″ Border on my Palma rifle for a time. Velocity was about 10 FPS below that of my 30″ Border. SD’s and ES were superior from the longer barrel, as was the sight picture. This was with Varget powder.

And if you want to see what 40"+ does 338 bullets

http://riflebarrels.com/long-barrel-velocities/

All the best
Trevor
 
My experience is limited to 154 Scenars, and 155 Sierras, Hornadys and Noslers. DCRA style target shooting. "Palma" style long barrels, 29-30 inches.
Without any pressure issues (including hot weather shooting), the 154/155s have a sweet spot @2950, AMAXs would make 3050.
Run the 154 Scenar through a ballistic program with a mv of 2950. Strong performance for a .308.
 
You must log in or register to reply here.
Back
Top Bottom