Looking for the Title of a story

If this is meant to be elsewhere, please let me know. I once read a story about a soldier who was in a horrific assault, who was then grafted into a large battle mech. As the story goes on, more flesh is taken until eventually only a spinal column and brain are left inside a gel-sack, and the machine has been upgraded to the point that it now has a super-punch that is powered by artillery shells in the shoulder. Some search engines showed alot of similar stories, but I can't find the right one. Anyone know this tale by title?