I own 3 1100s all made in the 70's to the early 80's. None have even close to the low recoil of the New Competition 1100. I have a Jack West on one of mine.
I don't know how much the Rucker Auto Buster vs the Over Bore barrel effect the total, but in combination they make a very noticeable difference in the competition 1100.
I have an 1100 from the 1970's. Stan Baker overbored (.740") 30" bbl with his forcing cone AND PORTING work. Gun has been shot by a few friends that own 1100's, all felt my gun had a "softer felt recoil". I can not say the porting helps or hurts anything re recoil. I will say the gun has no problem cycling or functioning as intended. Marc