@j17wang, First Gun in Chinese would be more like the first weapon created by development (for PLAAF) rather than meaning the first firing of gun in anger. This is afte rall a Test Flight Bureau.
Me again with what appears to be an as yet - at least to me - unknown unit patch? From what I understand, it is said to be the "second J-16 brigade within the NTC", which would fit to the 15th Air Brigade if I'm not mistaken.