chim came up with the idea to modify a late model BuckMark buffer for the Challenger. I modified it like he described and made another minor change. The material that they use can be easily ground or filed. I don't know what it is made of, but since they are cheap it doesn't pay to take a chance. Brownell's has very fast shipping. Since you have to pay for shipping anyway I would suggest that you make up a list of items that you may need and get them at the same time and save on shipping cost. By the way, the BuckMark has two different buffers, make sure you get the right one. Brownell's has a schematic that you can look at.
I purchased a couple of BuckMark recoil springs for my Challenger and a few buffers. You may want to ask chim what he recommends for spares.