I have been reading a lot about guns in Wikipedia. I know much of the terminology of firearms. However, I was wondering why some firearms such as shotguns and rifles have very long barrels opposed to small handguns such as revolvers and pistols, that normally have shorter barrels.

I know, there are functional differences between the types of weapons I described: Shotguns normally shot shogun shells with pellets, Rifles have "rifling" inside their barrel, pistols are made to be held with the hand without shoulder support, revolvers have a cilynder of cartridges that rotates. (This descriptions is rough and doesn't intend to be a very accurate defintion of every gun type).

Nevertheless, shotguns rifles and snipers normally have longer barrels than pistols and revolvers (althought there are handguns with long barrels).

Here there is an article about the subject

The question is: What advantages and disadvantages come with differences in length of the barrel? And does a longer barrel improve accuracy?

I have made up some hypotheses. I list them here. :

-Longer barrels are used for higher explosive ammo because the barrel can contain the expanded gases and made them push the bullet over a longer barrel, giving the bullet more energy.

-Longer barrel means the sight is further and thus one can make more precise shots because the two aligning marks are further, and thus in order to seem aligned to the eye they have to be in "more aligned" than with a shorter barrel.

  • $\begingroup$ "But the question is, shotguns rifles and snipers normally have longer barrels than pistols and revolvers". That's not a question. In fact, this entire "question" is just a bunch of lecturing that never actually asks anything. Closing this mess. $\endgroup$ – Olin Lathrop Oct 22 '16 at 17:01
  • 3
    $\begingroup$ @OlinLathrop: While it is considered best to have the question in the body, the title is quite a clear question. $\endgroup$ – Wasabi Oct 22 '16 at 17:34
  • $\begingroup$ @OlinLathrop The question is what advantages and disavantages come with diffeerences in lenght of the barrel, and if they improve accuracy. $\endgroup$ – Santropedro Oct 22 '16 at 17:34
  • $\begingroup$ Longer barrel and longer [iron] sight base are not exactly the same thing. You can extend the site base while keeping the barrel length the same. For an example, look at Rk 62 which has got a longer sight base than the AK-47 on which Rk 62 is based. $\endgroup$ – Nick Alexeev Oct 22 '16 at 22:49
  • $\begingroup$ @NickAlexeev Your comment says "sight base" and "site base", also, what means "sight base"? It seems to me that the ak 47 has got the most far away sight. But I think I got what you are saying, you can control where the "sights" are independently of the barrel lenght, and yes, that's a very good observation, I forgot to say that in the post. $\endgroup$ – Santropedro Oct 22 '16 at 23:17

The short answer: Yes, a longer gun barrel improves accuracy. Theoretical accuracy of handguns and rifles is driven by rifling, barrel length, and bullet mass.

  • Rifling: When the bullet travels through the barrel, the rifling (helical grooves in the barrel) forces the bullet to spin by converting some of its forward kinetic energy to angular momentum. This gives the bullet gyroscopic stability. Remember, a gun without rifling is a musket - without spin, the bullet trajectory is unstable, like a 'knuckle ball'.

  • Barrel length: A longer barrel extends the time time interval where chamber pressure acts on the bullet's mass. Therefore, a longer barrel increases the exit velocity of the bullet and the effective range of the bullet. Friction limits the allowable barrel length.

  • Bullet mass: Increased bullet mass increases the bullets inertia (resistance to external forces). Therefore, the bullets trajectory is less effected by external forces such as cross-winds or contact with obstacles (like brush, etc.).

Note that these factors are interrelated. Rifling is a function of barrel length (Twist per Length). So a longer barrel (rifle) imparts more spin to the bullet than a short barrel (handgun). But exit velocity also depends on bullet mass and barrel length. The bullets exit velocity and stability (its effective accuracy) depends on rifling, barrel length, and bullet mass. (Common calibers and their respective rates of twist are listed here).

Standard shotguns do not have rifling. Their accuracy is more relative because they shoot multiple projectiles. Longer barrels create a more focused scatter shot than shorter barrels. The focus of the scatter is commonly modified with chokes. enter image description here

A few practical considerations:

  • Sight base: For a gun without an optical scope, a longer sight base increases accuracy. Misalignment errors by the shooter are reduced from trigonometry between the front and rear sights. However, long distance accuracy demands minute angle corrections only possible with optical scopes - the length of sight base is irrelevant.

  • Heat strain: Gun barrels often get very hot from high energy rounds and high rates of fire. As a result of temperature differences, the barrel deforms/bends - therefore, the accuracy changes from the first shot to the last. To minimize heat strain and deflections, free floating barrels, and/or larger diameter (or fluted) barrels are used to maintain accuracy.

Ultimately, there are advantages to each type. Hand guns excel at close ranges where maneuverability and rate of fire is critical. Shotguns dont require absolute accuracy to hit the target (an advantage when shooting at moving targets like birds) but have a very limited range. Rifles offer the best accuracy and range but reduced manueverability and often reduced rates of fire (depending on the action: Bolt vs Semi-Auto vs Full-Auto).


Also, for accuracy, the quality of the bullet or projectile - if it is "out of balance" ie the centre of gravity does not coincide with the axis of rotation then it will "fly off" or miss its intended target. And if you want a reference try "The bullet's flight by F. W. Mann" long out of print though.


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