How to mount a Holosun 507K X2 on a Weaver base: it is a Holosun K (modified RMSc) open-emitter reflex, so it needs a Weaver-compatible Holosun K (modified RMSc) mount, not a Picatinny one.
Updated 05 September 2026.
Fit a Holosun 507K X2 on a Weaver base
The Holosun 507K X2 is a Holosun K (modified RMSc) optic. Here is the Weaver-compatible mount it needs and why a Picatinny footprint mount may not seat on a Weaver slot.
The Holosun 507K X2 is a Holosun K (modified RMSc) optic, so it needs a Holosun K (modified RMSc) mount. On a Weaver base that mount has to be a Weaver-compatible version: Weaver slots are narrower and spaced differently from Picatinny, so a full-width Picatinny recoil lug may not drop in.
If the only Holosun K (modified RMSc) mount you can find is Picatinny-cut, the cleaner fix is to replace the Weaver base with a Picatinny rail, then use the standard Holosun K (modified RMSc) Picatinny mount. Check the mount clamps square before locking it down.
- ›Holosun 507K X2 on a Picatinny railthe Picatinny case
- ›Holosun 507K X2 footprint and mountthe optic
- ›Weaver railthe base
- ›Picatinny mount on a Weaver railwhy the lug matters
Questions and answers
Fit a Holosun 507K X2 on a Weaver base?
The Holosun 507K X2 reaches a Weaver base through a Weaver-compatible RMSc-footprint Picatinny mount. A Picatinny version of the same footprint mount may not seat, because its 5.23 mm recoil lug can be too wide for the 4.57 mm Weaver slot. Buy the Weaver-cut mount, or fit a Picatinny base first.