Well, I finished the rechamber to 454 on the gun I bought for my son and it was pretty easy. Removed the barrel, then drove out the pin retaining the extractor, which was the pin closest to the chamber end. I used plenty of FP10 oil and followed the instructions for the reamer which were very clear. Taking my time, the re-chamber was done in less than 10 minutes, stopping several times to brush shavings off the reamer and reapply cutting oil. I marked the underlug using the smallest set of harbor freight stamps, which as I recall cost me less than $5. Then I did it on the second 45bc I bought for my Dad.
One thing I noticed during the initial few turns of the reamer on both guns was a high spot that the reamer caught on. Once this was carefully removed the reamer progress was very smooth. Perhaps the improvement in accuracy reported by others is the result of removing this uneven transition in the throat?
I'm only moderately mechanical, and my gunsmithing experience is not broad, so if I can do this, anyone who is patient and can follow instructions will have no problem.
The reamer and donation will be back in the mail to Tim tomorrow