Holosun HE510C
An open-reflex rifle dot with a big window, solar backup, and multi-reticle versatility.
The Rundown
The Holosun 510C is a popular open-emitter rifle red dot known for its large, square viewing window and excellent value. Like its pistol siblings it offers a selectable circle-dot reticle, Shake Awake, and — a signature Holosun feature — a solar panel that can run the optic in bright light even if the battery dies. The wide window makes target acquisition fast with both eyes open.
As an open design it's lighter and cheaper than enclosed tube optics, with the usual tradeoff that the exposed lens can collect rain or debris. For a budget-conscious AR build, a truck gun, or anyone who wants a big-window dot without Aimpoint money, the 510C is a community favorite that punches well above its price.