Does this sound like the ignition switch?

74 Duster- It's been difficult to start lately. I noticed what I think is a little binding when turning off the key. But here is what is happening- I turn the key and she turns over, no problem, but wont start. I noticed when I go to turn the key off, it starts to fire up. It sounds like " Blup" and then shuts down. I did test power to the coil a while back and it was good. Sound like a key switch?