336 mount/rem 870 for red dot

[jmitc4]

I recently bought the vortex venom to swap out my true glo sight that came with the gun (870 sops turkey/pred). The venom shares the same footprint as the FFIII. For Remington's that have been drilled and tapped at the factory, will the 336 base bolt into these factory holes? I have looked and can't find actual dimensions on the 336 base bolt holes. I would rather have the sight as close to the receiver as possible without a picatinny rail, but don't necessarily want to put additional holes in my receiver. Thanks.

[turkey_slayer]

The holes on the 336 are 1/2" apart tapped 8-40. I don't think that the remmys come from the factory like that but could be wrong