This is largely a means of grinding from the reinforcement materials that was added to strengthen the buffer tube/extension place, and reprofiling the region to make it resemble the first A1 spot. This will incorporate some welding or filling of some type. Use the images beneath as an example: AR15.COM https://claytonodqja.blogdal.com/31664976/rumored-buzz-on-colt-python-6-for-sale