The Effects of Accuracy Regarding Short Barrels

Factors affecting the accuracy of rifles are nearly always surrounded by controversy, debate and misinformation. The effect of barrel length on a rifle's accuracy is a factor that has been hotly debated. Conventional wisdom holds that longer rifle barrels are more accurate, but the truth of the matter is somewhat more nuanced.

  1. Conventional Wisdom

    • The assumption that a longer rifle barrel is more accurate is founded on a number of factors. The greater separation between the front and rear iron sights on a longer rifle can help increase accuracy by forcing a marksman to more exactly line the sights up and provide a straighter shot. However, most of today's shooters, especially those shooting at long ranges, use an optical scope, rendering the entire point moot. Longer barrels also allow for greater powder burn times, but only to a point.

    Burn Rate

    • A bullet is propelled down a rifle barrel by the expanding gasses released when gunpowder in the cartridge explodes. Broadly speaking, as long as the powder is still burning and those expanding gasses are being given off the bullet is increasing in velocity. As soon as that process ends, either because all the powder has been consumed or the bullet leaves the barrel, the bullet's acceleration ends and it immediately begins to slow down. The exact loss in velocity depends on the powder and bullet being used, and its effect of accuracy largely depends on the range to the target.

      Many smaller bullets that are coupled with fast-burning powders are well equipped to deal with a shorter barrel because it takes relatively less barrel length for the powder to burn completely. Larger bullets using slower-burning powder are more sensitive to barrel length because it takes a longer time for the powder to burn, and as the bullet is moving while the powder is burning, more barrel length is needed to reach maximum velocity.

    Barrel Harmonics

    • Stiffer barrels are better. This is a well-accepted truism, and is the reason for heavy or "bull" barrels. A thicker, stiffer barrel vibrates less, and that reduced vibration translates into a more predictable flight path for the bullet. A given barrel will be stiffer the shorter it is, thus giving shorter barrels an inherent advantage in efforts to reduce barrel vibration.

    Human Factors

    • One downside to a longer rifle barrel is its weight and unwieldiness. While a heavier rifle is inherently more accurate, if it is used in the field the increased exertion required to carry it around can decrease a shooter's accuracy. This kind of human factor is a serious consideration for a field marksman, especially when shooting in remote or mountainous terrain.

    Tests

    • Staff at the GPS Defense Sniper School cut the barrel of a Remington 700 rifle chambered in .308, a moderately-sized bullet, from 26 inches to 18 inches. At 100 yards there was no change to the point of impact; at 920 yards only two additional minutes of elevation were needed to compensate for the decreased barrel length.