Scope Mount Finder

Fit a Weaver mount on a Picatinny rail

Why a Weaver mount usually seats on a Picatinny rail, and the one thing to check.

Direct fitA Weaver mount usually fits a Picatinny rail: its 4.57 mm cross-bar drops into the wider 5.23 mm Picatinny slot. Confirm it clamps square.
Opticscope or ring on a Weaver mountWeaver cross-bar 4.57 mm
interface
Mountthe Weaver mount clamps the Picatinny rail directly
seats on
RailPicatinny rail (MIL-STD-1913)5.23 mm slot, wider than Weaver
Fit readoutBench figures
Fitment
Why it fits
Weaver cross-bar is thinner than the Picatinny slot
Check
Weaver spacing may not index a slotted Picatinny recoil lug
What to fit it with

A Weaver mount has a 4.57 mm cross-bar, which drops into the 5.23 mm Picatinny slot, so it usually seats. This is the easy direction of the Weaver-to-Picatinny relationship.

The catch is spacing. Weaver slots are not on the Picatinny pitch, so a mount that needs to index a recoil lug at a set spacing may not line up. Check it clamps square and locks before use.

Related fitments

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