Just saying, I used a Ronsin Tech Torch, here, and it worked perfectly to knock out my rear assembly..
They're about $25 at Ace Hardware. Originally bought it to use last 4th of July to light fireworks, lights fires quickly, its over all a pretty neat little lighter to have around the house. In fact, we have two of them. But I only had to use one on my Mosin. Three minutes of heating back and forth on one side of the rear sight, and it popped off really quick.