Shok buffs can help keep a standard dust-cover gun (SA, Colt, Kimber etc) from getting cracks around where the recoil spring guide rests. Back in the 80's and 90's, it was very common for guns to crack there with the heavy roundage we poured to them (I cracked at least three frames and one more than once). One of the things the S_I guns beefed up was the dust cover (for easier scope mounting and frame durability). In an S_I gun I would not worry about a shok buff. I've never had reliability issues with a shok buff and usually run the .90-.125" sizes. For a while, you could get .200" and even then I didn't have issues. There was a short period when it was "cool" to run a stack of buffs so that the gun cycled shorter and theoretically faster. That didn't last long.
I still run buffs in my 1911's for long range sessions, but take them out for carry and matches.