Greg Walley
Member
By removing the imperfections left behind from the reaming process. Brass flows into these imperfections (often seen as rings) and makes for difficult extraction with high pressure loads. I've never seen a chamber reamer from anyone cut a chamber with a finish that didn't require a little light honing/polishing.
With mid size reamers (PPC size) in predrilled and prebored 416 SS within 0.020" of finish ream size, I ream at 300-350 RPM - SFM 40 (about 0.0017 IPR). I use 10% Cimcool flooded through the bore with a high pressure pump. I drive the reamer with a dead-center and chamber between centers. I can easily get over 100 chambers with Pacific or JGS reamers before resharpening. I've never had a reamer grab, and I've never broken any fingers (knock on wood!).
Out of the 350-400 barrels a year that I chamber, I've only had chatter problems three or four times in ten years because the reamers were ground incorrectly. Those reamers did not come from JGS or Pacific. I'd like to know what super-duper metal and heat treating process Red Elliot used. I've got a 308 reamer that he made with well over 200 chambers and it still gives a good finish. That reamer almost feeds itself into the hole (special grind?). I was told by another reamer maker they were made from F-2...which is a steel used for rock chisels.
Usually the throat and the shoulder of the reamer wear out first. I inspect the chambers with a halogen flashlight, borescope, and check for dimensional tolerances with gage balls.
Greg Walley
Kelbly's Inc.