Home Forums Hunting & Shooting Ask The Gunwriters 308 velocity in 16 1/2 inch and a 20 inch barrel

What kind of velocity can one expect in a 308 with a 16 1/2 inch or a 20 inch barrel using 130 grain bullets

Hodgdon shows a bunch of loads at 2800 or so out of a 15" test barrel.

In my experience, it depends on the barrel.

Don’t know about the velocity, but I have a fair notion of the report, more than I want…

Enuf to kill chit at most any reasonable range.

The first thing I killed with a 17" '06 , and 180 gr factory load bullets, was a ram at 330 yards. The two important things beyond bullet construction is knowing the range and the load's trajectory. Velocity is over-rated.... JMO. Still to be considered sometimes....

Others have need for a crony- I've never owned one.

I guess I don't know what I'm missing? I'm still happy.

https://matchgrademachine.com/velocity-testing-thompson-center-barrels/

maybe around 100+/-fps, muzzle velocity is different for every barrel.

It depends on the individual barrel. Some barrels are slow, some are fast, and some are "half-fast."

It also depends on the powder, primer, etc.

I would expect a 20" barrel to have 125fps additional velocity over a 16.5" barrel. tdoyka is probably the closest with right around 100 fps.

I usually experience a 200fps difference between a 16.25" and a 26" barrel 308 win. 21" would split the difference perfectly and so 20" would normally be a touch slower. Individual barrels will vary in actual performance.

18" barrel: https://www.barnesbullets.com/wp-content/uploads/2021/05/7.62x51-18.0in-Barrel.pdf

20" barrel: https://www.barnesbullets.com/wp-content/uploads/2021/05/7.62x51-20.0in-Barrel..pdf

I found that it varied with the load and can run from 25-100 fps going from a 22" barrel to a 20" barrel. In my rifle's well-worn 20" barrel, the 130-grain TTSX lost 82 fps but was still faster than anything else at 3,003 fps.


Okie John

I compared various .308 Winchester loads, including some with the 125 grain Nosler Ballistic Tip, from 16.25" and 24" barreled rifles. The short barreled 308 impressed me with both accuracy and velocity:



I think 2905 fps is worthwhile.

I've seen that little 125 grain Nosler Ballistic Tip in action on a fat whitetail buck, and it did real well at about 120 yards. The 130 gr Barnes TTSX would also be an interesting option...

Regards, Guy

16.5" barrel? Begs the question - why?

Maybe close to legal minimum to make room for the length of a can?

If you average this all out it coms to 27.375 fps per inch. This fits what I've seen with various bullets and powders across my herd of 308 chambered rifles.

My Savage hog hunter has an 18”, kills hell out of pigs at 275 yards with a 150 grain GameKing.

Yeah, I’d expect around 25-30fps per inch.

I sent off a magnum-contour 22” .308 bolt gun not long ago for a chop/thread at 17”. Makes for a very pleasant shooter with a 7” suppressor.

One of my favorite barrels is 42” long.

Is it on a 308?

One of the interesting things about this sort of conversation is that only rarely does anymore figure out how much velocity a typical 125-130 grain .30 caliber hunting bullet loses at 100 yards--or any other range.

Most hunters have been fixated on muzzle velocity ever since the appearance of smokeless powder, even thought it's made less and less difference as powders and bullets have improved....

The only way to know is to shoot the loads from a 20" barrel, cut it to 16.5" and measure the speed at 16.5". I'd expect 50-100 fps less. BUT... you can see 100 fps difference between 2 different 20" barrels. Both of them will lose 50-100 fps when cut, but since one of them may start 100 fps faster than the other it is entirely possible to find an individual 16.5" barrel that is a bit faster than another 20" barrel. OR.... an individual 16.5" barrel may well be 200 fps slower than another individual 20" barrel.

Out of an 18” BAR MK3 I’m shooting the 150 gr Lapua Mega SP at 2730’s. This has been great whitetail medicine. Not what you asked, but some info that may help. Powder selection may make a difference by going to something on the faster side. Pretty sure that one was with CFE223 or PP2000.

Not bad at all if you're wearing ear protection.

Actually, no, "something on the faster side" won't get more velocity in shorter rifle barrels--if that's what you're suggesting. The same powders that get the highest velocities in longer barrels also get the highest velocity in shorter barrels. This has been proven many times.

My 308 has an 8 twist 18" barrel. Strictly suppressed. My hunting load is 178 grains at 2595. Hope that helps

My 16" barrel 30/06 still gets 308Win velocities, just saying...

IMHO the only barrel length/velocity test worth the time to read is same barrel, starting at ~25, 26, 27" in length, same lot of ammo, same day.


Shoot & chrono. Chop off an inch, shoot & chrono. Repeat till you or the barrel has had enough. Like Mule Deer said, some barrels are fast, some are slow, etc.

Rifleshooter.com has done a bunch of these test with various calibers. Seems I have to dig around the sight to find the test sometimes, but they're there, & they are very informative. A 20 - 25 fps change per inch can still be a aproxx number, but some calibers at certain lengths may surprise.

I did something like that years ago with a 7x57 I built, though not by shortening it an inch. The barrel was a pre-chambered 24" Shilen I bought from Brownells, on a 98 Mauser action. I tried it at 24" and came up with two main loads, one for the 140-grain Nosler Solid Base (pre-Ballistic Tip) and IMR4350, and one for the 160-grain Partition and H4831--the military surplus version. I then shortened the barrel to 21" and tried the same loads.

At 24" the 140 load averaged 2892 fps, with the chronograph 15 feet from the muzzle. At 21" it chronographed 2828 fps. The 160 load averaged 2733 at 24", 2647 at 21".

The difference per inch with the 140s was 21.3 fps, with the 160s 28.6 fps.

No, it's a .45.



Best I can do at 50 offhand....


I like smoke.

I don't fiddle with short barrel CF rifles very much. EX: My .45-70 has a 30" pipe.

I remember a published experiment, years ago, where some "looney" DID cut a barrel down in small increments.
The results were quite interesting, and every inch was not the same. At one cut, the velocity actually increased!
Wish I remembered who did that.
Maybe the article was titled "All Inches are not the Same". Not sure.

If you will search , I posted about a dozen barrels I cut and measured velocity. I'll see if I can find those.

Phil Sharpe, one of the very first gun writers to own a chronograph, ran an experiment exactly like that, which if I recall correctly was published in his fine book, Complete Guide to Handloading. He mentioned some increases in velocity as the barrel was cut, attributing it to variations in bore/groove diameter.

I also had the same sort of thing happen when chronographing various factory and handloads in a pair of CZ 550 9.3x62s, a rifle with a 23.6" (60cm) barrel, and the full-length-stocked version with a 21" barrel. A few were a little faster in the shorter barrel, with all chronographed during the same range session....

I have no chronograph, but that 17" '06 bbl has killed the chit out of things for me over the years with mostly factory ammo. 1.25 MOA. First thing it did after I chopped the bulge (not mine!) out of the bbl muzzle was a Dall ram at @ 330 yards. Later took a caribou one shot at about 370... Best $85 I ever spent on a used rifle.... a Ruger 77 tanger.

It ain't the MV , it's knowing the range, and the trajectory.

I have a well broken in kimber mountain ascent. which i shot at factor 22" and cut down to 16" all measures with a 7" thunderbeast and magneto speed and 5 shot strings. Of the lot the federal terminal ascent has impressed the hell out of me for velocity retention and terminal performance at lower speeds.
Factory barnes ttsx 130gr 3170fps pre 2989 post
Factory federal terminal ascent 175gr 2640fps pre 2508fps post
48gr W760 w/ sierra gameking 180gr 2578 pre 2425 post

I found that data I was looking for.
https://www.24hourcampfire.com/ubbthreads/ubbthreads.php/topics/90491/1

Why I built mine.
155gr scenars are right around 2600fps with 47 gr RL 15 out of my 16” Douglas.

I have a Ruger Hawkeye Scout (16.5”). 165 NBTS over 46 of Varget was good for 2675 fps with suppressor. It was much better than I anticipated.

Have Christensen Arms Ridgline FFT 20" .308. 155 Scenar-L over 45.4 TAC and 210M suppressed getting 2880 fps.

I tested loads for accuracy in my 18" barreled Ruger Scout and ended up with that exact same recipe - 46gr. of Varget under the 165gr NBT. I really don't care a ton about velocity as long as it's reasonable, but I'll say your results are encouraging. I would have been happy with around 2,600-2,650 fps, but maybe I'll be closer to (if not break) 2,700? I hope to chrony that load over the next few weeks.

Some factory 308 win ammo chrono speeds recorded from a 20 inch Savage Model 10 scout rifle. Rem 150gr 2746, Rem 180gr 2506, Fed. GMM 168gr 2576, Win Fail safe 150gr. 2765, Win 150gr B. tip 2525.