To Rail Or Not To Rail

Twilight:2000 happens as some long held paradigms in infantry weapons changed.

The Austrians and British had changed over to bullpup rifles which used magnified optics instead of iron sights.  The Germans were working on a caseless bullpup rifle that used a scope instead of irons.

The US and Canada were slicing the carry handles off their M16 derivatives and replacing them with a rail which wasn't specific to a particular optic.  The US with the, now, ubiquitous Picatinny rail, Canada going with a modification of the ancient Weaver system.  Picatinny is also a modification of the Weaver system, but different from the Canadian version.

It's the slots.  Weaver and Canada use narrower slots (0.180" vs 0.206").  Weaver doesn't specify spacing of the slots, Canada and Picatinny do.

Canada and Picatinny use different spacing (0.394" center to center for Picatinny) with the Canadian system getting 14 slots in the same space as Picatinny getting 13.

This creates some incompatibilities.  Don't get too down on Canada here, they simply licensed an existing Weaver modification from A.R.M.S. mere months before the Picatinny rail was developed and NATO adopted it.

Anything designed for a Weaver base will fit both.

Anything designed for a Canadian rail will fit a Picatinny rail.

Some things designed for a Picatinny rail will fit on a Weaver or Canadian rail.  Trial and error here.

And then there's the Soviets and Warsaw Pact...

Nominally there are two standard side-rails for their weapons.  The AK pattern and the SVD pattern.

The same scope can be found with either mounting style.  Except for the mounting, they are identical.

Later scopes, outside the scope (pun) of T2K have a mounting system that can used with both style of rails.