Especially with the "approval" of silencers for hunters, the topic of barrel length has become more significant in recent years. In many hunting, weapon, and ballistics forums, there are now contributions where there is lively discussion about how barrel length interacts with the respective caliber to affect the effectiveness of the projectile, its speed, trajectory, and energy. Many who now want to retroactively add a threaded barrel to their weapon for the purpose of using a silencer are now confronted with this topic. In the context of such a post-processing of the barrel, it is usually shortened.

Many are therefore anxious about such an intervention in their weapon and fear, above all, that they will encounter problems regarding accuracy afterward. But how do barrel length and caliber really interact? And by how much does shortening a barrel reduce projectile speed and energy with the same load?

Unfortunately, this cannot be answered with a blanket formula, as there are simply too many parameters that are significant for projectile speed. In addition to caliber, parameters such as case volume, bullet shape, and the burn rate of the propellant powder are also relevant. Especially with the latter, there can be individual deviations for each cartridge.

Even with standard rifle calibers with case lengths in the range of 60 to 65 millimeters, such as 7 x 64 or .30-06 Spr., there are usually speed differences of 30 m/s to about 50 m/s due to these deviations with barrel lengths between 660 millimeters and 510 millimeters.

How much a barrel shortening further increases these differences almost always depends on the combination of the barrel used, caliber, bullet type, etc. However, a fundamental loss of performance can usually be documented after barrel shortening. It should be noted here that this usually occurs in ranges recommended by gunsmiths for barrel shortening, which do not lead to significant consequences for the hunting use of the weapon. Whether a projectile weighing more than 160 grains hits the target at 780 m/s or at 740 m/s is unlikely to make a relevant difference for hunting success, even in the case of a moving hunt, where it is known that shots are also fired at moving game.

It is therefore always important to first seek the expert opinion of a knowledgeable person, usually the trusted gunsmith, and to consult them about the planned barrel shortening concerning the caliber used and the load employed.

It is generally known that different loads of the same caliber fired from the same weapon can lead to different point of impact locations. Likewise, bullet speed and bullet energy can vary depending on the load. On the other hand, these mentioned properties can also vary when using the same load from two different weapons of the same caliber.

It remains to be noted that the shooting result depends on many parameters, of which barrel length and caliber are just two, and that the hunter should fundamentally ensure before hunting that the chosen combination of weapon, silencer, and ammunition leads to the desired result regarding point of impact and bullet effect. If a non-negative deviation is observed after the installation of the silencer or any other structural change to the weapon, one should try to find out with which other load the desired result can be restored.

*This refers to the amendment of the Weapons Act on 01.09.2020, after which hunters were to be allowed to use silencers during hunting nationwide