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

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.