Slide/Frame impact protection
I put this Sprinco unit in both my Kimber 1911, and a Para P-12-45, and I have never looked back. It is a buffer, in that a short spring is picked up very near the end of rearward slide travel by the spring cap.
It is also what designer Alan calls a "recoil reducer". I find that the gun feels tighter and much more damped, rather than a lot of slide inertia slinging itself back and forth. It helps me to get follow-up shots lined up faster.
He says they have a couple of test guns with 200,000+ rounds and no cracks in the frame. (I can't wait to see the new ultra-slo-mo videos I've heard about, showing frame flex during fire cycle, both polymer and steel frames).
The only down side is some extra effort and technique to manually lock the slide back. That was easy to master and should only be an issue for those with reduced hand/arm strength.
I know some don't like a long spring guide, but reliability has been flawless for several thousand rounds now in the Kimber. And mine is the +P version, which will sometimes cause a problem with light target loads, but at least for me, no problems there either. I sold the P-12 and last I heard the new owner kept it in too.
B.