
To review what this project is about -- most factory 357 rifle barrels have a sucky "toilet bowl" throat instead of a proper rifle throat. I want to see what a 357 will do with a good throat. And if that works out, I'll put a strain gage on it and use it for pressure testing my pet 357 loads.
My previous attempts to cut the perfect 357 throat did not work out -- either there was a problem with my homemade reamer, or most recently with the 1/2 degree throat, it just didn't want to shoot.
Perhaps if I had tried lots of different bullets and lots of different loads I would have eventually found something that shot decent, but that's not what this project is about. We're looking for the perfect 357 cast bullet throat, or at least a pretty good one, anyway. And nobody is even sure what the perfect cast bullet throat looks like!

So I will set the 27" Green Mountain barrel back and start over with a fresh 357 mag chamber. This time we'll try a 1.5 degree per side throat, because that's a very popular design.
I'll reuse the 357 maxi reamer to cut the chamber. The throat gets a separate throating reamer -- I like doing it separately so I can control the throat independent of the chamber. Here's the homemade 1.5 degree reamer. The .347" pilot is a very snug fit in the Green Mountain barrel, and the 0.379" section will be supported by the 0.380" chamber. The idea is that the reamer can't help but cut concentric with the bore.

While some say that "D" reamers do not require relief, I've found that they cut much nicer if you grind relief.

That's as far as I got today, this project will take a week or two working in my so-called "spare time."
