Do Heavy Bullets Cause Rifle Groups To Widen?

A reader submitted a question about heavier bullets in reloads possibly causing rifle groups to widen.

Q: When I’m not on the firing line, the rest of my spare time is spent at the reloading bench and I’ve run across an odd anomaly I hope you can help me with. When I go to heavier match-grade bullets with a slightly improved ballistic coefficient, my rifle’s groups seem to widen. Any idea why?

A: Bullet length could be the culprit. To vary weight in a particular brand and caliber of a bullet, manufacturers wind up shortening or lengthening the projectile’s overall length. If everything else remained constant, and only the bullet weight was altered, your rifle’s rate of rifling could be too slow to stabilize the longer and heavier projectile. Before you abandon the heavier bullet and its improved ballistic coefficient though, try a few different reloading recipes from different manuals. Bullet length is only one of the many possible causes.

Another possibility, although unlikely, is the barrel getting so hot it begins to warp. Or mirage is causing an aiming issue.

Since your goal is most likely maximum accuracy, it would be wise to try a wide variety of different loads. There isn’t much predictability when it comes to knowing which your particular rifle will prefer and thus, shoot better groups.

Finally, some guns just don’t agree with certain loads. With safety in mind, keep experimenting and do your research. Eventually you will find the recipe for what you are looking for.

Please submit your questions to shootingsportsusa@nrahq.org.

Lead photo: Berger 175-grain .308 OTM bullet.