Lt. Haines' bio also showed that he was an assistant instructor in engineering. With his educational background and involvement with testing, I think it would be safe to say that he left his thumbprint on the design/improvements for the Model of 1896 regarding both the magazine rifle and magazine carbine. He was likely sought out by the Springfield Armory for both his engineering education and his cavalry experience when it came to the carbine design improvements.
I could find no more information on him outside of being on a list for promotion to captain in February, 1901.