If one were planning to buy/build a lightweight rifle in 308, what kind of barrel would be the best bet? Let's say we have a planned weight for the barrel, and that weight will not change (the volume of steel used in it is constant). Is it better to go with a longer, skinnier barrel, say a thin 22" or 24" one, OR is it better to go with a shorter, heavier 20" barrel?

I know that a shorter barrel will have an effect on velocity, but this is not important to me. Balance and accuracy are better. I have seen some really tiny groups shot by 16" barreled AR-15s, so I know that accuracy is definitely possible in a short barrel. In fact, I believe that a shorter, heavier barrel will be so much stiffer that accuracy can't help but be better than in a long thin barrel (assuming all other factors are equal).

Anyone done any testing to prove this out (or disprove it)? Any other opinions out there on how this might play out?

hmmm...I'd guess that the heavier 20" barrel will be marginally more accurate, but why not just reduce shank length on the 22" barrel and get a grade up from featherweight for same overall weight?

FWIW, I have seen 22" FWT. .308 barrelled rifles shoot sub-moa -- is that not accurate enough?

barrel length in and of itself does not affect accuracy, but it does affect harmonics by way of changing weight and the muzzle's relationship to nodes.

If you had two barrels with the same volume of steel, one short and one long, the shorter one will likely be more accurate because a fatter diameter means it will flex less. Less muzzle deflection results in consistency/accuracy. That accuracy difference may be too small to measure or huge, there's no good way to predict it.

I personally think a longer skinnier barrel feels better to point than a short fat one of the same weight.
Thats kind of a personal choice.

I've probably suggested this a million times...
If you want something light and handy look into the Tikka T3s. I have a T3 Lite in .308 and love the rifle. It has a 22" (it's actually some funny length like 22-5/8" or something like that) barrel and weighs in at 6lbs 3oz unscoped. With a Leupold VXI on mine I still have a rifle that weighs less than an unscoped Rem 700. It'll outshoot the vast majority of sporter weight rifles in its price class too.
It's not considered a featherweigh or ultralight rifle, but its at the lower end of the weight scale for sporter rifles.

I regularly get three shot half inch groups at 100 yards with 168gr Black Hills Match ammo and better than 0.75" groups with good hunting ammo.

Precision Shooting had some articles on research on this subject by benchrest shooters. It seems the "sweet spot" they found was around 21".

If you are looking solely for the influence of barrel diameter vs. length for a given weight, then the answer is "short and fat" is more accurate. Mind you, there are so many other factors involved (quality of parts, smithing etc), that you may or may not be able to spot the difference.

Dan Lilja has this article on his website about the influence of barrel diameter and length on accuracy.

- mike

Guys, I'm not a gunsmith or an engineer, so please don't laugh at my thought.

Why not use the longer, heavier barrel and flute it down to the desired weight?

I am interested in why this would not be an acceptable compromise.

quote:

If one were planning to buy/build a lightweight rifle in 308, what kind of barrel would be the best bet?

IMO a Douglas XX grade featherweight 22"

Shorter and heavier is always better. Keep in mind the barrel is like a tuning fork, the shorter it is the less vibration you will get.

Flutting is a very good answer to your problem. I personally don't like the looks, but from a physics standpoint it is proven better. If you had 2 barrels of the same weight, one was larger in diameter and fluted and the other one was smaller in diameter, but not flutted, the fluted barrel would theoreticaly be more accurate. This tends to be more true in light weight barrels than heavier barrels. The reason is that the barrel is almost as stiff as if it had never been fluted, its the same as cross bracing a building structure.
If velocity is not important, I would go with a 20" barrel in #3 or #4 contour flutted to achieve your desired weight

Since you're probably not an engineer, I'll try to explain it in layman's terms.

For barrels of equal stiffness [that means the exact same same cross section dimensions] the amount the barrel will vibrate (deflection from a neutral postion) at the end is a function of the cube of the length. This is why length is generally not condusive to accuracy.

Sure, you can go to a "premium" grade long barrel and compare it to a stock short barrel, but this is not an apples vs. apples comparison.

I've heard so much BS about fluting making barrel stiffer. If you start with a given o.d. and cut flutes in it, you will make it less stiff. Guaranteed. The only way a fluted barrel will be stiffer than a round one is when they are of equal cross section weight, then the fluted barrel will have a larger o.d.