What muzzle velocity can I expect from 150gr and 168gr from a 308 20" rifle?

[adrenaline681]

I dont own a chronograph and im trying to aproximate how much muzzle velocity 2 rounds will give me with a 20" barrel:

a) 150gr Hornady FMJ with 44gr of IMR 4895 (my guess is 2650 fps)
b) 168gr Hornady A-Max with 44.5gr of Varget (my guess is 2600 fps)

If anyone has any experience with these loads or a rough approximation of what muzzle velocity could I be getting, please let me know!

Thanks!

 

[big cal]

depende on the twist you have
150g 2660-2665
168g 2600 for 44g 44.5 look for high pre.back off .5 to be safe
have fun

 

[rick357]

There is no way to tell accurately by looking or talking about it. You can get a bunch of reloading handbooks and look at the values they got with their equipment to get a rough idea.

Get 20 rifle makes with the same barrel length and a bunch of extremely well made match ammo and muzzle velocity will vary a lot - at least 100fps if not more. You can either chronograph them, or shoot at various ranges (I suggest 100, 250, 500, 750) without touching your sights/scope until you get an average POI drop at each range then work it out with a ballistics program.

 

[scourge18a]

I have an 18.5" Savage 10 PSR
168 grain AMAX seated 0.015" off the lands
Lapua brass
BR-2 CCI primers
46 grains of Varget.
2733 ft/sec

And 168 Berger VLDs with same Lapua Brass, 46 grains of Varget seated 0.015" off the lands at 2760.


2 groups at 300 yards with the AMAX

 

[bigedp51]

Very good test of .308 barrel length and velocity below with charts and lots of data. I have a .308 Savage Hog Hunter with a 20 inch barrel. And you will loose less than 100 fps vs a 24 inch barrel but a increase in muzzle blast and kick.

308 Winchester / 7.62x51mm NATO: Barrel Length versus Velocity (28″ to 16.5″)
https://rifleshooter.com/2014/12/308-winchester-7-62x51mm-nato-barrel-length-versus-velocity-28-to-16-5/

 

[Ganderite]

I would guess about 100 fps less than a 24" barrel, but as has been stated, velocities vary a lot from barrel to barrel. I have a pair of 308s with consecutive serial numbers. Velocities with the same ammo are about 150 fps apart.