Is a 20 inch barrel good enough for a 308 hunting rifle?

[denton]

One of my favorite long guns is a 600 in 308, with an 18" barrel.

It does not give me as much MV as a 22 or 24, but it is light, handy, and plenty potent. And when you touch it off, there isn't any question about whether it lit or not!

How much you lose by cutting off an inch of barrel depends on the bullet, the powder, and how long the barrel was before you cut the inch off. Cutting an inch off a 29" barrel probably costs you roughly 15 FPS. Cutting an inch off an 18" barrel probably costs you more like 35-50 FPS. The powder burns out long before the bullet reaches the muzzle, but the compressed gas continues to accelerate the bullet.

The muzzle flash you see is because the compressed gas is out of oxygen but hot enough to glow. When it hits the air, some components in the gas re-ignite. It would be really unusual for still burning powder to reach the muzzle.

With a short barrel, bullet selection becomes more important. Sierra hunting bullets tend to need to impact at about 2100 FPS to open reliably. Nosler Partitions open reliably at 1800 FPS. So with a Partition, your bullet will open at longer range. There are plenty of bullets that will do this.

IIRC, with 165 grain bullets a max load gives me around 2650 FPS but I load down to 2550 FPS for comfort. It's quite adequate for anything within 350 yards. If I need to reach beyond that, there had better be a darn good reason.

 

[heeler]

I have used my old 1972 built Remington 600 Mohawk in 308,equipped with the factory 18.5 inch barrel for several years walk hunting for deer and hogs with very lethal results.
I had a guy with an Ohler cronograph measure a three shot group of mine using Federal Premium 165 gr.BTSP coming out of that 18.5 barrel and the average was 2550 fps three feet in front of the muzzle.
I dropped a buck at a lazered 244 yards DRT with that rifle and ammo combination.
A .308 can handle a short barrel quite well and still retain efficient killing power down the distance line.

 

[browningguy]

They work fine, I have a Ruger 77 RSi with the 18.5" barrel in .308, and two 30-06's with 20.5" and 18" barrels.

 

[helotaxi]

Velocity should not be negatively affected by a 20" barrel length unless you are loading with a very slow burning or progressive powder. Generally speaking, with most conventional smokeless powders achieve full burn and, therefore, essentially peak velocity by the 16" - 18" range.

It doesn't work that way. Percent of burn is not usually even worth looking at. Most .308 loads don't completely burn the powder charge in a 26" barrel. 3031 is the notable exception to that. The .308 in particular has a very large expansion ratio for its case capacity. This means that it doesn't maintain pressure very well and also means that slower powders can't build pressure fast enough to reach peak allowable pressure before the volume behind the bullet has increased at a rate faster than the gases from the burning propellant expands. For this reason, .308s like medium-fast rifle powders. Also for this reason the .308 doesn't generate enough gases to see a lot of benefit from a long barrel. Compare this to a cartridge with a high case volume to bore ratio and a low expansion ratio. Cartridges such as the .243, .25-06 and 7mm Mag benefit greatly from a longer barrel because the smaller bore in relation to the powder charge means that a lot of gas volume is created and pressure is maintained at a higher level for a longer length of bore.

The other question that may be relevant is the barrel twist rate and intended bullet weight. 1 in 12 is pretty common for .308 so unless you are cutting down a barrel with a lesser rate of twist and/or intent on using very heavy for caliber bullets, anything in the 150 - 180 gr range should adequately stabilize in a 20" barrel. 20" is a good length.

The difference in velocity for the various barrel lengths in the .308 means that the barrel twist is either fast enough or not independent of the barrel length. Within the normal velocity range of the .308 the difference in the Miller Stability Index for a particular bullet isn't affected appreciably by the 250fps or so difference in velocity between a 16" and 26" barrel.

 

[Averageman]

18 inch barrels would seem to me to be about perfect for a .308.

 

[helotaxi]

Other than muzzle blast, I would not disagree if it was intended for hunting purposes. If legal, 16" with a suppressor would be about perfect IMO.

 

[uvausmc]

My Ruger Frontier killed two whitetails back to back a few seasons ago. They never noticed that I only had a 16" barrel. As long as you're not looking at shooting extreme ranges <20" is fine. Also remember the shorter the barrel the stiffer it is so it is theoretically more accurate.

 

[Redneck with a 40]

I've got a Remington 700 SPS tactical in .308 with a 20" barrel. I only punch paper with this thing out to 350 yards and its sweet! Short, handy, powerfull and fun!

 

[243winxb]

20" = less velocity + More noise.

 

[jerkface11]

If it were a .30-30 would you be asking if a 20" barrel was long enough?

 

[T.R.]

This dandy antelope buck was taken at well over 300 long strides. My 20 inch barrel .308 performed flawlessly at this long range. Plain FEDERAL Classic ammo was used.

TR

 

[helotaxi]

"Less" is only relevant in context. The argument could be made that 26" offers less velocity than 30" and more noise so the 30" is better. The argument could also be made that 20" offers more velocity and less noise than a 16".

"Less" and "more" are not the argument that relevant. "Adequate" and "acceptable" are the salient points. Velocity is certainly adequate from a 20" barrel for the .308 and whether the noise level is acceptable is up to the individual.

 

[ball3006]

Several deer that I shot with my 18 inch barreled carbine didn't notice the barrel was too short by some people's standards...........chris3

 

[denton]

Most .308 loads don't completely burn the powder charge in a 26" barrel.

Common misconception, I'm afraid.

People see muzzle flash, and assume that the powder is still burning. In almost every case, the powder is all burned in less than a foot. The muzzle flash is bright for two reasons: 1) The propellant gas is hot enough to glow, even though the fire is out, and 2) The propellant gas contains hydrogen and other flammable products. When these hit open air, they have oxygen again, and re-ignite.

 

[helotaxi]

Based on Quickload simulations, not muzzle flash. Muzzle flash indicates pressure, nothing else. Regardless, completeness of burn isn't a valid goal for either velocity or accuracy. Almost no rifle completely burns the powder charge in a barrel of reasonable length. If it did, then there would be significant wasted pressure potential and lost velocity.

 

[Fremmer]

hbeautiful rifle maxi. like that full stock.

 

[FMF Doc]

I would say no, as long as it is stiff enough, and has good harmonics. The USMC Sniper rifle the M40A5 has a 20" barrel, and they seem to do just fine with it. No complaints out to 1000m.

 

[Art Eatman]

Looks like the question is quite well-answered.