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You mean a Hatsan Escort ... Optimas are over and under.
It's not just the distance between the pins you need worry about, where I think they are are closer together anyway, but also their relevant position on the receiver which are in fact in a different place. The Hatsan pins are both the same size too, where the 870 pins are a different size.
But for whatever other reason you ask, the pins on the 870 are 2.020" apart centre to centre.