.308 Winchester Ballistics

[Timradcliffe345]

What is the difference, ballistically, between a 308 Winchester out of a 20" versus a 24" barrel? I'm planning on shooting out to 500-600 yards. Is there alarge tradeoff going down to a 20" barrel. If not, the 20" is lighter and more compact. Please help me out. Thanks and God Bless the US.

 

[Slamfire]

This is not an exact comparison, but I have data that is close between 18”, 22” and 26” 308 barrels.

Basically my measurements show about a 25 fps loss/increase per inch of barrel.

At 600 yards, it all depends on what you want to do. The longer barrel gives extra velocity and I would think that is an advantage a long range.

PTR91 18" barrel


150 gr Australian Ball MF83 headstamp

30 April 2008 T = 75 °F

Ave Vel = 2599
Std Dev = 23
ES = 63
High = 2630
Low = 2567
N = 10

150 gr Hornady FMJBT 43.0 grs AA2520 wtd Lot 9595 Czech Mixed LC WLR
OAL 2.785

30 April 2008 T = 75 °F

Ave Vel = 2544
Std Dev = 32
ES = 84
High = 2574
Low = 2490
N = 5



Ruger M77 Tactical, 26” Barrel

150 gr Australian Ball MF83 headstamp

30 April 2008 T = 62 °F

Ave Vel = 2819
Std Dev = 19
ES = 64
High = 2859
Low = 2795
N = 10



150 gr Hornady FMJBT 43.5 grs AA2520 wtd Lot 9595 Czech Mixed LC WLR
OAL 2.785
30 April 2008 T = 65 °F

Ave Vel = 2756
Std Dev = 28
ES = 97
High = 2806
Low = 2709
N = 10



M1a 22” Douglas 1:10 barrel

150 gr Hornady FMJBT 43.5 grs AA2520 wtd Lot 9595 Czech Mixed LC WLR
OAL 2.785
18 May 2008 T = 70 °F

Ave Vel = 2700
Std Dev = 30
ES = 85
High = 2736
Low = 2651

 

[dagger dog]

I have a side note on the .308 Win. data page in my Speer #13 manual that as a rule of thumb(and I'll probably get shouted down) that you can figure roughly 20fps +-for every 1" of barrel and I think I remember the reference going down to an 18" bbl., but I don't remember the velocity gain for over 26". But I take it as the ammo and bbl has to be the same. In other words the article I read started out with a 26"bbl and actually cut 1" off and recrowned for every test down to 18"

 

[doctorxring]

.

Difference is around 100 fps.

This amounts to around 40 yards of ballistic effectiveness.

If you want to tinker with numbers, this is a good ballistic
calculator --

http://www.handloads.com/calc/


have fun ! dxr

.

 

[Shawnee]

Another important - but unmeasured - difference between a .308 from a 20" barrel and one from a 24" barrel is the noise. The .308 from a 20" barrel is LOUD, and that is not going to help your target shooting.

 

[zeke]

DSA 16 inch carbine with permanetly attached muzzle break. Makes for a 14 in rifled barrel. Hirtenberger, Port and SA all get very close to 2600 fps, above 60 degrees.