Any pointers on rechambering? Did you do it by hand? Any advice would be appreciated.
I'd ask any more knowledgeable than myself to chime in if I misdirect or omit.
By hand. After having cleaned the barrel well and removed the ejector, I made several measurements, observations and an impact "cast" of the original chamber. The impact cast will provide a measurement to assure good pilot fit and for checking the walls afterward to make sure you didn't make the chamber wider or oval.
Measure the depth of the rim cut and compare to SAAMI specs. If on the low to mid point, you can use something like "white-out" to coat the rim cut so you can STOP cutting before you cut the rim cut any deeper. I used the reamer borrowed from GBO and took tips from Tim and at least one other person on GBO who had done some work on a handi barrel for me.
I set the clean barrel vertically in a bench vise, over a catch pan for the cutting oil and wrapped/tied a rag around the outside of the chamber area to catch chips and oil - because I use a LOT of oil, use a sharp tool. Inspect the reamer before using it whether new or borrowed and don't use it if it's buggered. I've seen some real experts do some amazing work with junk tool, but I am not an expert.
Get set up and have everything (lots of paper towels already torn off the roll) within arms' reach, get any extraneous crap out of the way and take your time.
When it's time, don't forget:
1) DO NOT turn the reamer backwards. It can damage the reamer and it can also wedge a chip under a cutting edge and instantly make the reamer that much bigger in diameter. I've seen a master "make" a reamer larger by inserting a small corner of a paper shop towel under one of the cutting edges. Not on a gun. It worked and the hole was enlarged by the amount he predicted.
2) Have and use lots of good cutting fluid.
3) Stop and clean ALL the chips out of the chamber and the tooling often. I'd say I did it at least four times, maybe more?
4) Steel yourself and approach the actual cutting as if you've done a hundred of them. You'll muck it up or you won't. You will be less likely to if you're not hesitant and indecisive.
5) Keep the reamer parallel to the bore/chamber, period. You may want the breech low enough to bend over the tool so you can apply a LITTLE of your weight to it instead of trying to turn the reamer, press down on it AND keep it straight with all the articulation available in your arm - shoulder, elbow, wrist, phalanges,....
6) Use a T-handle for the reamer so you don't "waller out" the chamber. A follow-up impact cast should come out the same as the first one in the original 357 Mag part of the chamber.
7) Make sure you hold your mouth the same way from start to finish. I don't think exactly HOW you hold your mouth matters as much as the consistency in how you hold your mouth.
8) STOP and check with a dummy cartridge when you get close. You'll have to clean the oil out and mark the bullet with a sharpie to see where the rifling is. If you start cuting again, don't forget to STOP before you get to the bottom of the rim cut. I made two dummies - one with the RCBS 35-200 and another with a RDO 359-190. Make sure your dummy cases are not too short. I like using one right at max length, if I can find one, or at least one of the longest ones I have which is not above max length.
As far as the "feel" RADIALLY, I didn't get as much feedback as when
tapping a hole and not at all the same on the Y-axis, because the reamer will not pull itself in. Again, DO NOT turn the reamer backwards. Steady downward pressure - just enough to CUT is required. You should be able to turn the reamer smoothly, if not easily, meaning that some torque is required - it's not like trimming a brass case in terms of "ease."
The feedback you get from the reamer is the big mystery until you've done it once and I can't explain it. Grasp the T-handle firmly and lock your wrist/elbow and turn at the shoulder with your muscles firmed up and rigid but not "charlie-horse" tight. Watch the reamer in the hole and keep it straight - don't want the hole bigger around, just deeper.
That may sound like a lot, but once you've cleaned the chips out for the last time, it doesn't seem like it.
Again, anyone with more experience or better ideas, please chime in.