Lead and Throat?

[mao0720]

Can someone help me better understand the lead and throat length when looking at a chamber or reamer drawing. On my 308 the lead is 2.1315, and the throat is 2.3892. Which of these is where the rifling starts? It looks to me that the rifling starts and 2.3892, but then what is the lead? Thanks for the help.

 

[ar10ar15man]

first off..not all reamer makers use the same/correct terminolgy for the same attributes.

from my jgs print.( and from pacific tool and gage..dave kiff...my current reamer grinder)
lead is a cylinder forward of both the neck and any taper from neck to lead....
throat is the tapered section forward of lead where rifling will begin..the transition from cylinder to rifling..

some reamer makers use these terms in reverse....

gonna go check saami...

LEADE (LEAD)
That section of the bore of a rifled gun barrel located immediately ahead of the chamber in which the rifling is conically removed to provide clearance for the seated bullet. Also called Throat or Ball Seat.

THROAT
See Leade (Lead).


basically saami does not recognize the cylinder section forward of the "chamber" and the throat/leade..as a seperate attribute.....