Is your Crosman 1377 shooting high

The problem forever with the 1377 (not so much the 1322) is the rear sight block is too tall when compared to other handgun rear sight units which sit barely above the surface of the receiver in a dovetail. In fact, most hand gun units are actually let into the body of the receiver flush, with just the notch blade sat above the receiver. On the Crosman, this already tall unit (relatively speaking) is then fixed above the barrel on the rear bolt housing….Taken together, it might just be the tallest rear sight ever fitted to a hand gun.

This usually does not prove a problem with the 1322 at 20 yds due to shooting pellets of almost twice the weight, with a more curved trajectory.

Best idea is to go with a bolt on sighting aid, such as red dots which have limitless adjustment, or try some of these new ultra heavy hunting slugs.


 
You could try a metal breech. If that does not werq maybe a metal barrel clamp which the gun really needs anyway. Really not positive either of these will fix your problem but they are both great upgrades for the gun.

https://www.ebay.com/itm/164987830713

I made my own sights modified a Gamo rifle sight and made a special adjustment screw. This combination werqed out trick but did not get to use it long as it was stolen shortly after I finished it in late 2010.