Scope Mount Finder

Fit a Picatinny mount on a Weaver rail

Why a Picatinny mount often fails on a Weaver rail, and what to use instead.

Will not fitA Picatinny mount often will not fit a Weaver rail. The 5.23 mm recoil lug is too wide for the 4.57 mm Weaver slot, so use a Weaver mount or fit a Picatinny base.
Opticscope or ring on a Picatinny mountPicatinny recoil lug 5.23 mm
interface
Mountthe Picatinny lug is too wide for the Weaver slot
seats on
RailWeaver rail4.57 mm slot, narrower than Picatinny
Fit readoutBench figures
Fitment
Why it fails
Picatinny lug 5.23 mm will not enter a 4.57 mm Weaver slot
Fix
use a Weaver-compatible mount or add a Picatinny base
What to fit it with

This is the direction that fails. A Picatinny mount with a full-width 5.23 mm recoil lug will not drop into the narrower 4.57 mm Weaver slot. Forcing it either will not seat or damages the rail.

Use a mount cut for Weaver, or replace the Weaver base with a Picatinny rail so the mount fits properly.

Related fitments

Sources: Picatinny vs Weaver rails, Weaver Mounts · Scope mounting: Picatinny vs Weaver, NRA SSUSA · MIL-STD-1913 Picatinny rail dimensions, Wikipedia