Lloyd, I had several .264's, and I really liked the caliber, BUT I had the same problems with mine you are having with yours..shot super one day and terrible the next...the only one I had that was excellent was a pre 64 model 70 westerner..It would drill them in there ... but I foolishly let my pals talk me into trading for a 7mm...
One of my shooting buddies here in town, has had excellent luck with H870, and 140's.. but I doubt it is available any more...