Converted military rifles often experience issues with which component?

The correct response highlights that the eyepiece bolt, which is part of the sighting system, can pose issues when military rifles are converted for different uses or calibers. This is particularly relevant because the original designs often catered to specific requirements, and modifications can lead to misalignment or malfunction of the optics, impacting the overall accuracy and usability of the rifle.

In contrast, while the trigger mechanism, magazine feed, and barrel twist are also integral components of a rifle, they do not typically experience the same level of frequent complications when a rifle is converted. The trigger mechanism might be adjusted but is less likely to malfunction directly due to conversion. The magazine feed may also require some adaptation but generally maintains functionality unless there are major design changes. Barrel twist does play a role in accuracy related to the type of ammunition used, but it is less commonly affected during the conversion process compared to the potential issues with the eyepiece bolt which directly links to the sighting efficacy.