I have finally decided to succumb to putting a side mount scope base on my pre angle eject Winchester ‘94 30-30.

I can get a Weaver #3A side mount for a ‘94 .375 Big bore locally but the Weaver chart says the correct mount is the #3D.

What is the difference? Will the #3A fit or not?

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We need more information about your gun, because “pre angle eject Winchester 94” covers a lot of ground.

Winchester didn’t drill and tap for a receiver sight until after WWII. The Weaver 3B, 3C and 3D mounts attach to the factory receiver sight holes and the lever pin stop screw hole. Winchester had to move the receiver sight mounting holes forward on the Big Bore because of the reinforcement at the back of the receiver, so I’m pretty sure the hole spacing is different. I sold my .375 Big Bore several years ago, so I don’t have one to measure.

I looked at the Weaver fit chart online and there seems to be some discrepancies. You might want to double check your information.

Here’s what I found:
Pre-64 94 - 3D (48415) I’ll add that this will only work for a factory drill 94, after about serial number 1,900,000
Post-64 94 & Trapper - 3B (48412) I believe the difference between the 3B and 3D is the size of the lever pin stop screw hole
Big Bore .375 94 - 3C (48413)

The Weaver 3A (48403) is a generic side mount that requires drilling and tapping of the frame. I would not recommend you have that done.

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