system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Why are semi-auto marksman rifles not as accurate as bolt-actions?
gpt
There are a lot less variables with a bolt action. They are simple and strong, and that makes for less ‘play’ in the action. Semi autos use a gas system, rechamber based on recoil and basically have more moving parts, which is more that can throw off the ballistics of a given shot. They are also often constructed to be more portable, and light. Which results in shorter barrel length, which means reduced accuracy. (I seem to have been informed this is more to do with velocity than ballistics, fair enough)

Most modern sniper rifles also use more powerful rounds than ‘traditional’ rifle cartridges, such as 338 lapua magnum. These rounds offer superior ballistics, but are impractical for use in a marksman rifle, on the move with an infantry section.

That said, it’s not always true. A modern marksman rifle is produced to a higher standard of accuracy than a bolt action sniper rifle from 100 years ago.