Measuring Headspace for 338 Win Mag
- Thread starter stevelsd
- Start date
I suffered a few case head seps as a young loader and quickly learned the false shoulder method to extent my brass life. It’s paid off in keep my fingers, eyes, etc and brass life and it takes but a few extra minutes.
RiverRider
Handloader
- Dec 9, 2008
- 1,463
- 123
I bought the RCBS headpace gauge many years ago when I was just getting into centerfire rifle reloading. I learned pressty quick that it did not give me an absolute measurement, but it was good for relative meaurement.
These days I just use my old Stoney Point bullet comparator using an insert that fits somewhere near the middle of the shoulder. I know that's not "the" datum line...I don't think there's a tool out there that will put you precisely on "the" datum line, and a relative measurement is just fine. I only use the measurement to keep track of how much I am changing shoulder bump as I adjust my sizing die (I leave them set once I get them where I want them). I DO NOT just go by the measurement to determine where I want the shoulder, I go by feel---at least on a bolt rifle. For my ARs I try to keep shoulder bump at a minimum for case life, but for reliable function you have to be willing to go an extra couple of thousandths.
If you do the arithmetic, turning the locking ring on a sizing die the equivalent of a one-second tick of an analog clock (which is 6 degrees) changes shoulder bump by about 1.2 thousandths of an inch.
These days I just use my old Stoney Point bullet comparator using an insert that fits somewhere near the middle of the shoulder. I know that's not "the" datum line...I don't think there's a tool out there that will put you precisely on "the" datum line, and a relative measurement is just fine. I only use the measurement to keep track of how much I am changing shoulder bump as I adjust my sizing die (I leave them set once I get them where I want them). I DO NOT just go by the measurement to determine where I want the shoulder, I go by feel---at least on a bolt rifle. For my ARs I try to keep shoulder bump at a minimum for case life, but for reliable function you have to be willing to go an extra couple of thousandths.
If you do the arithmetic, turning the locking ring on a sizing die the equivalent of a one-second tick of an analog clock (which is 6 degrees) changes shoulder bump by about 1.2 thousandths of an inch.
