Scope Mount Finder
Scope Mount Finder / Every rail, tube and red-dot footprint

3/8 inch (9.5 mm) dovetail rail (rimfire tip-off)

The tip-off groove on US 22 rimfires, its base and top width, and why it usually shares rings with the 11 mm metric dovetail.

Rail cross-section, not to scale
DesignationUS rimfire tip-off
Rail standard
Base width
3/8 in (about 9.5 mm)
Top width
about 1/2 in (12.7 mm)
Type
clamped tip-off groove, no cross-slots
Found on
US 22 LR rimfire rifles
Accepts
3/8 inch dovetail ringsadjustable 11 to 13 mm dovetail ringsdovetail to Picatinny adapter

The US 3/8 inch tip-off is about 9.5 mm at the base and about 12.7 mm across the top, cut as a plain clamped groove with no recoil slots.

Because the 3/8 inch base and the European 11 mm top width overlap, many rings marketed for one will clamp the other. Measure the actual groove before buying, since a ring set for the wrong width will not tighten square.

A Picatinny optic reaches this rail through a dovetail-to-Picatinny adapter base, the same route used on 11 mm airgun dovetails.

Rings and adapters for a 3/8 inch dovetail
Search Amazon for 3/8 inch dovetail scope ringsaffiliate searchFind 3/8 inch dovetail scope rings on eBayaffiliateSearch Amazon for 3/8 inch dovetail to Picatinny adapteraffiliate searchFind 3/8 inch dovetail to Picatinny adapter on eBayaffiliate
Related rails and fitments

Sources: 11mm and 3/8in dovetail interchange, Pyramyd Air · How to measure 11mm, 3/8in and 13mm dovetails, RimfireCentral