Conch, I see at the end of your post you mentioned the '7.62x54 project' ... well, I wasn't in on that, but I did take one of my 7.62x39 Handi barrels (I bought three such rifles a few years back; one became my 303 British, another became my 7.62x54 and the third is still in 7.62x39 as a spare for years from now when I eventually wear out one of the other two.
Both the 303 and the 7.62x54 have proven to be excellent shooters and I'm glad I did it. The camber reaming was done by hand, by me, and it was very easy ... like most things worth doing, you just take your time and use loads of lube. For both of these I simply removed the ejector/extractor and tied off the barrel to a post, using the rciever lug as my 'stop' to prevent clockwise rotation as i cut, with the chamber facing upwards ... i.e., tied upside down to the post (becasue I don't have a lathe). I then pushed a tight 'plug' of cotton wool down the - barrel about 8" in. I then poured my cutting oil in the hole - used Brownell's 'Do-Drill'. I then gently inserted the reamer until it came to rest on the opening of the chanber and proceeded to turn the 'T' clockwise using only very light pressure (handly any - as the reamer is very sharp at this stage and cutter under the weight of the 'T'-handle and the reamer alone will start removing steel. After about 50 turn there was a noticable 'opening' to the chamber and the cutter was in about 1/2"-3/4" by them. I removed the cutter ... lifting vertically upwards and making sure to NOT reverse (go anti-clockwise), actually still keeping a little clockwise rotation going as I lifted. I took a toothbrush and lightly brushed away the cuttings and carefully went back in. As the reamer went deeper I found I had to increase both the force applied downward (inward) a little (not by much ... stay 'light') and in rotation (again, not much; stay light), and repeated the removal/cleaning about every 50 turns. After about 10-15 minutes .... Voila, as they say ... done! I poured out the cutting oil by pushing the cotton plug out the muzzle into a waiting cup covered with a cotton rag which caught the oil and filtered out all but the smallest metal fragments and poured that clean oil back into the 'Do-Drill' can for future use ... I guess I maybe 'lost' an ounce of oil in all this. I then cleaned-out the 'new' chamber with a chamber brush, wool mop and many passes with a piece of cotton until it was spotless under a hand-held mafnifier and light. The I dropped in many different new and full-length resized 303 case and checked that the rear of the cases were totally 'flush' with the rear face of the breech ... and they were ... got lucky the very first time ... woo hooo!
.
Then, within an hour, I was at the range and making 1"-1 1/2" groups with the 303
I am sure that those gunsmiths out there might be less impressed with the foregoing procedure, but it did produce very happy results. The 303 brass I get out of this chamber is perfectly fire-formed to the chamber, so I only have to neck side now, and there is none of that 'bulge' one so often sees in once-fired 303 brass from being fired in a 'war-standard' sloppy chamber as you so often find in milsurp-303s.
It is too bad that NEW didn't have the foresight to include the 303 in their line-up. Their arguement (as they stated in a letter back to me back in the 90s) about not wishing to make their rifles available for shooting milsurp (non-SAAMI Standard) ammo would mean (as I somewhat cheekily responded to that letter
) that they would be withdrawing production of the .223 Rem (5.56), the 308 Win (7.62), the 30-06 and the 45-70. I never heard back from them after that