There have been a number of complaints regarding this issue, and calls to "fix the Survivalist's rifle bug", however J.E. Sawyer had this to say on the matter:

It's not a bug. The Survivalist's Rifle was used by the Survivalist for decades and shows signs of improvised repair (the clamps on the foregrip wood, the mismatched wood furniture, etc.). The bent front sight is damage that the Survivalist couldn't or didn't repair and just adapted to using as-is. If you aim at the right front post, that's where the bullets are going.

Personally I think it is a lot more realistic this way considering how old the weapon is, and doesn't break immersion as much as a centuries old weapon being in pristine condition.