Rummer,
I shoot Lightfield Htbrid Expanders out of my 870 with a Hastings rifled barrel with great success. If both the copper solids and the lightfields are shhoting good for you I would choose the lightfields since they have a higher muzzle energy I beilive 2500 ftlbs versus 2000 for the copper solids. Also the lightfields expand alot more due to them being lead versus copper. As far as the pedals breaking off, I hunt with people that use them and they have not had that problem with them.
TH