Picatinny rail (MIL-STD-1913)
The military standard rail: its slot width, spacing and depth, and why a Weaver mount drops on but a Picatinny mount does not always drop onto a Weaver.
The recoil groove that a mount's cross-bolt or recoil lug locks into is 5.23 mm wide and the slots are spaced 10.01 mm centre to centre, so a mount cut to the standard indexes at the same points on any MIL-STD-1913 rail regardless of maker.
Because Picatinny slots are wider than Weaver slots, a Weaver-pattern mount with a thinner cross-bar usually drops onto a Picatinny rail, but a Picatinny mount with a 5.23 mm lug will not fit the narrower 4.57 mm Weaver slot.
An 11 mm or 3/8 inch dovetail is a clamped groove, not a slotted flat, so a dovetail scope ring cannot sit on a Picatinny rail without a dovetail-to-Picatinny adapter base.
- ›1 inch scope on a Picatinny raildirect fit
- ›30 mm scope on a Picatinny raildirect fit
- ›Aimpoint Micro on a Picatinny raildirect fit
- ›Weaver mount on a Picatinny railusually fits
- ›11 mm dovetail optic to a Picatinny railneeds adapter
- ›Weaver rail4.57 mm slot
Sources: MIL-STD-1913 Picatinny rail dimensions, Wikipedia · Picatinny rail measurements, Picatinny.de · Picatinny mounting standard, OpticFootprint · Picatinny vs Weaver rails, Weaver Mounts