Here is Trijicon's oficial response....
The difference will be in the height of the front sight. The GL104Y has a lower front to compensate for a heavier round. If you are shooting a lighter weight round like a 185gr you should be ok for the most part. Thank you for your patronage to Trijicon products. Have a good day.
Aaron Kyser | Order Processing Specialist
Phone (248)960-7700 Ext.202
Fax (248)960-7725 | P.O. Box 930059
49385 Shafer Ave. | Wixom, MI 48393
Trijicon® Brilliant Aiming Solutions™