Okay, I laid hands on some FEDERAL generic M193 and shot the thing again today. Three 5 shot groups, all of them in the 1.24" neighborhood, all of them with 4 of the 5 shots well under an inch--4 in .671 in one case. THAT's more like what I expect this gun to do.
But dunno if last week's 2+ inch "patterns" were the fault of Rem ammo or not. Someone suggested I check my scope mounts so I did. Found that what I thought was finger-"tight" MIGHT have been allowing a little movement so I laid some pliers upon the carry handle nut. Whether it was the ammo or strapping down that nut, I can't say but the gun seems to be running fine again. Oh, BTW, when it was shooting good BEFORE the Remington ammo, I only had the scope nut down "finger tight" so draw your own conclusion.
Thanks to all who responded with ideas and words of encouragement in the original thread.