With just about every 7 Rem Mag I have worked with 64-67 grains of 22 with a LR Mag primer makes about 3050-3100. If you're up over 3100FPS it's hot and chances are you'd have locked up your gun if you were really getting 3200 with a 160 in a 7 Rem. Not sure about your ladder tests, as I don't do them myself, but I'd load 63-66 grains in 1/2 grain increments and see where your velocity settles and try that. If the gun isn't bent, it'll shoot well in that charge range. 22 is a weird powder and lot to lot variations have driven me nuts over the years, but it is really good once you get it dialed in.
