M42 mirror clearance

Hi all,

I've got a ludicrous idea for a camera 'hack' that uses an M42 body, but it sort of hinges on how deeply I'd be able to set a particular lens inside the mount. I'm wondering if someone with an M42 SLR would mind measuring the distance between the edge of the mirror and the front of the mount for me. I know there's likely some variance from model to model, but a ballpark is useful.

Thanks a bunch!

I just set a caliper depth measuring end at 0.4 inches and it cleared the mirror of an ES-II near the top.

Since it follows an arc, you should be able to go deeper if the edge of the rear element is closer to the center.

Thanks a bunch! Chances are I'll never end up doing anything, but it seems feasible.