Scope base spacing

[Incitatus]

I was just about to buy a base for a new barrel when I read a comment about it.  The comment said that Weaver and Thompson bases do not have the same spacing between grooves.

Terrific.

I have one base that came with a barrel that I bought and I'd like to be consistant.  Anybody know how to tell different bases apart?  Or what the spacing is for Weaver's vs. Thompson's etc??

[Keith L]

I have never heard that before.  Weaver spacing has been the standard for that style of base for a long time.

[JustaShooter]

Weaver groove spacing has never been standardized like Picatinny has, so it is quite possible for two Weaver bases to be different.  If you are planning on moving a scope w/rings from one Weaver base to another without moving/removing the rings, you'd better make sure you get bases with the same spacing, which generally means from the same manufacturer.

Just a Shooter

[Lone Star]

I recently purchased a new 92A base for a new barrel.  All my scoped Contenders use the Weaver bases, and my scopes have always been 100% interchangeable.....until this last base.   The groove spacing is different, and to use one of my scopes I have to move one ring about 1/16".  A real pain, I plan to replace that base.




.

[Incitatus]

This is where I got my info from.

http://www.midwayusa.com/viewProduct/?productNumber=851268

A guy in a review said (about a THOMPSON base):

Jim Oneil of Cleveland, OH
Date posted: 1/6/2007
If you have a scope already set up on another barrel using a Weaver 92A base, this mount does NOT use the same spacing as the Weaver (mine came up around .030 short.). Bottom line, you can't swap scopes between different mounts. If you use a Weaver, stick with Weaver. If you already have the T/C mounts, stick with those.

Since I already have a base on one barrel, I was hoping to be able to maintain consistency. 

[Keith L]

I misunderstood the question.  The dovetail on the Weaver base is what I think is standard.  The cross groves to locate the mounts may not be.

[Incitatus]

I misunderstood the question.  The dovetail on the Weaver base is what I think is standard.  The cross groves to locate the mounts may not be.

Right, particularly compared to other manufacturers.  Thats why Im trying to figure out what I have already so that I can get the same thing.  Probably isn't worth all of the dead electrons that the question has caused already.

[Hopalong7]

   If it is a Weaver brand(not style) it will have 92A stamped on it.