roughing out chambers

[p17enfeild]

i have always chambered my rifles useing only a finish reamer in floating reaer holder as been an engineer by trade,machine tool fitter)i know that the head stock of any lathe is set to over come tool tip pushoff as is the tail stock in order for the lathe to trune true.,both centre line piont slightly to wards the apron of the lathe if at midl of the bed lengh and the circularity is only to 10 mirons avrage is 8mircon ish) so any boreing or drilling to rough out a chmber will result in a missalined chamber, if only by a few micros, i know that these shortern my reamer life. can any tell if they have tryed roughing a chamber out be for any ream work took place and what was the runout between the chamber and bore?

 

[p17enfeild]

the reamer life is not whats bothering me. chamber missalinrment is what iam try to asitain ?

 

[tightneck]

i have always chambered my rifles useing only a finish reamer in floating reaer holder as been an engineer by trade,machine tool fitter)i know that the head stock of any lathe is set to over come tool tip pushoff as is the tail stock in order for the lathe to trune true.,both centre line piont slightly to wards the apron of the lathe if at midl of the bed lengh and the circularity is only to 10 mirons avrage is 8mircon ish) so any boreing or drilling to rough out a chmber will result in a missalined chamber, if only by a few micros, i know that these shortern my reamer life. can any tell if they have tryed roughing a chamber out be for any ream work took place and what was the runout between the chamber and bore?

I do it every time.. I predrill the a hole just short of the shoulder,PPC,BR and other shortish cartridges), then re-indicate in the spot where the throat will be. Then I bore the hole to just under chamber dimension, and finally I run the finish reamer in to finish the chamber. I also use a floating holder and need the pilot to engage in the bore before the reamer starts cutting, therfore I can only bore out what the reamer will allow,the longer cartridges wont allow me to predrill/bore all the way to the shoulder). I indicate both ends of the barrel to have .0001" TIR or less before I finish the chamber, and rarley exceed .0002" TIR from the throat to the lands and grooves just in front of it after I am done. It works for me. We discussed this topic here not long ago and there are differing opinions on how to do it. I didn't come up with this method on my own either, I picked it up from other gunsmiths whose work speaks for itself. I feel that a tight,not too tight) fitting pilot is essential when using a floating holder as well.