To answer your questions:
1. I didn't let the barrel to cool down within 3-4 shots. I thought it looks heavy barrel (win model 70) and it won't heat up so quickly.
2. The barrel is not free floated as pre 64 model 70 the barrel is fixed on the stock
Not all pre 64 Mdl 70s have the barrel boss and configured with the associated forearm action screw (think featherweights). Might be worthwhile to try messing with the forearm screw torque level on your Mdl 70 or remove it to see what happens.
