I just checked my '86 (same receiver as '71) and it has a Lyman 66A. There is about 5/8" of windage adjustment thread, left of the aperture housing, probably 1/4" to the right. So the aperture is to the right of center in the windage adjustment slot.

The windage plate/bridge, including windage adjustment knob, is flush with the right side of the receiver, no overhang.

A 56 will probably have a longer windage plate to center the aperture in the windage slot. It will probably over hang the right side of the receiver by 1/4" or so. Would like to get that info from a 56 owner.

56 is probably the right one, 66 works very well and I would probably keep the 66, even if I had a 56. I like the way it fits the gun, flush on the right, without overhang.

DF

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Last edited by Dirtfarmer; 06/10/14.