I’ve had too many people tell me that longer barrels are more accurate and that short barrelled rifles are crap or that 26″ is the “most” ideal. A quick Google of the topic didn’t pull up any really decent articles either (Yahoo Answers does NOT count.) So, does barrel length affect accuracy?
Answer: Not really and it depends because there are a few factors at play. Especially for hunters, the differences between a 24″ and 20″ barrel are minimal.
Barrel stiffness helps reduce harmonics issues. Barrels whip when the rifle is fired and generally a thicker, stiffer barrel will be more forgiving and more accurate on a whole. Some thin barrels may have a particular brand or type of cartridge that they really like and will still be really accurate with. In general, shorter barrels with the same barrel profile will be stiffer than longer barrels just like how a long rope bridge will bounce a lot more than a short one. For short distance, you’re not hurt at all using a shorter barrel, which is why rifles like the Remington 700 SPS Tactical make do with stubby barrels. So score one for shorter barrels.
At longer distances, ballistics become important. Faster bullets drift less in wind, have less drop, and have shorter flight time. How can you get more velocity out of the same cartridge? Use a longer barrel and an appropriate powder charge to get more velocity. Optimal barrel length depends on the cartridge, which is why it’s common to see shorter barrelled 223 and 308 rifles but you’d be completely stupid to chop your 300 win mag rifle down to 18″. Still, score one for longer barrels, especially at longer ranges.
If you’re using iron sights, a longer barrel will give a longer sight radius and therefore, allow for more accurate use of those sights and fewer aiming errors. This also works on shotguns with keeping that bead way out there and is why many trap shooters use longer barrelled shotguns (along with the smooth swing of a longer barrel.) This effect is the most extreme on pistols, where the difference between a 4″ barrelled pistol and a 5″ is fairly significant (all other aspects the same.)
Does any of this matter for a hunter using a hunting rifle in a common hunting cartridge in a factory standard barrel length?
No! If you want a compact hunting rifle, use 308 or another short-barrel-length-loving cartridge in an 18″-ish rifle. If you want to hammer deer a couple of fields over, use your long barrel 300 win mag or 7mm rem mag. The truth of the matter is that other variables like ammunition quality, rifle setup, stock fit, trigger, etc are far more important for practical accuracy than barrel length.