FLYBOYJ
"THE GREAT GAZOO"
I don't know about later engines on the -106 but I do know that when we read about aircraft (especially high performance jet aircraft) having a top speed of XXXX or YYYY, many times those speeds (Vne) are attained at a point where either the aircraft isn't going any faster or if it's pushed will start to self destruct, the first thing to go is the nose cone which are usually fiberglass.That's a surprise: I remember hearing that the F-106B had a maximum mach number that was 0.1 higher than the F-106A owing to area ruling. With both aircraft having the same metallurgical construction, it seems the only thing that would have allowed one to go faster than the other was differences in drag.
Did later F-106 variants have different engines than earlier ones? That would change the balance...
My father in law spoke about the F-106, F-4, F-111 and B-1B having this characteristic.