Picatinny and Weaver rails
The slotted rails most mounts clamp onto. Picatinny (MIL-STD-1913) has evenly spaced slots of one width; Weaver slots are narrower and spaced irregularly. Weaver mounts fit Picatinny; the reverse not always.
What it means
Both are flat-topped rails with cross slots. A mount’s cross-bolt or recoil lug sits in a slot to stop the scope sliding under recoil.
- Picatinny (MIL-STD-1913): slots 0.206 in wide at a fixed spacing, so a mount can go in any slot.
- Weaver: narrower slots, spaced wherever the base maker put them.
What it changes in the field
A mount built for Weaver will usually sit on a Picatinny rail. A mount built for Picatinny may not fit a Weaver rail, because its lug can be too wide for the slot or the slot may not be where the lug is.
What to look for
- The maker’s wording. Mount pages say “Picatinny”, “Weaver” or both. Trust that over a photo.
- Slot fit. A lug that is loose in the slot lets the scope shift under recoil.
How we use it on this site
Mount pages list what the mount clamps onto in the maker’s own words.