.308 16.5" vs 18" barrel? (Velocity loss and practical differences)

[Winny94]

I've been told you lose 25-50 fps per inch of barrel, obviously that's quite a range. What is the velocity loss in a 16.5" barrel vs 18", and what kind of differences would I see at 600yds all else being equal between the two?

 

[Dallas4rceMarine]

most reloading manuals give a velocity difference of +/- 23fps per in for a .308

now every rifle is different, different chambers, bore, groove, twist, contour, etc… all factors that come into play.

best way to answer this is just search for what muzzle velocities people are posting they have for those lengths, plug that into a ballistic calculator and see the results for yourself. if its paper punching it doesn't matter much, if it is for hunting you might want more velocity.

that being said my 16" semi auto does just fine on steel out to 1,000 but I would not hunt with it past 500 out of personal preference.

i have a feeling within 50 comments this will turn to blondes vs brunettes...

 

[tipper]

There are only 2 Or 3 powders that would be all burnt in a 16" or 18" barrel.

 

[VJJPunisher]

The difference isn't gonna be enough to warrant the longer barrel if your intended purpose is a short package rifle, IMHO

 

[tipper]

I did this test today
American Eagle M1A 168gr, velocity on box 2650 dose not state barrel size

My results

Savage 10ba 24" Ave.: 2698.0

AR-10 18" Ave.: 2591.0

AR-10 24" Ave.: 2723.3

ar-10 16" Ave.: 2556.5

ar-10 20" Ave.: 2631.0

 

[tipper]

more that I did

ar10 20" Ave.: 2517.0 Blackhills 175 match

ar10 16" Ave.: 2423.6 Blackhills 175 match

ar10 20" Ave.: 2694.8 CFE223 46.5gr 175 BTHP

ar10 16" Ave.: 2621.8 CFE223 46.5gr 175 BTHP

AR10 24" Ave.: 2785.3 IMR 3031 42gr 168 BTHP

AR10 18" Ave.: 2663.7 IMR 3031 42gr 168 BTHP

 

[Vio515]

Along the same lines as one of the other comments, is the overall purpose of the rifle to be compact and easily maneuverable or do you want to scoot a bullet to 1000 yards with authority? If that is the goal the velocity gain from an 18 inch barrel will not be worth the length. My educated guess you is it would launch a 168 - 175 grain bullet around 2550 give or take 100 fps due to things like chamber size, barrel quality, moly coated or not, etc. Personally, would eat the velocity for an extremely handy rifle.

Matt

 

[D.ID]

I run a 16.5" 1in8 twist 308. Much to my surprise it shoves the 178 amax at 2650fps using lapua/210/43.0 varget. If your going short might as well go short.

 

[Niles Coyote]

[MENTION=99826]D.ID[/MENTION] I'd say you have a nice fast barrel. I get 2490-2500 with that same load combo (just with a 175 smk)on two remington factory barrels 20" in length and the same in a 1:8 AAC 18" and 2625ish in a rock creek @ 21.75", 26 remington factory varmint and 26" winchester stealth...

 

[BoilerUP]

I run a 16.5" 1in8 twist 308. Much to my surprise it shoves the 178 amax at 2650fps using lapua/210/43.0 varget. If your going short might as well go short.

Very fast barrel.

 

[308sniper147]

Very fast barrel.

My thoughts as well I haven't calculated my velocity up yet but I run 44.5gr varget in lapua brass behind a 155gr senar, out of a 26" barrel... With 10" extra barrel I guess I should have high hopes lol