Again...Freebore and headspace are not even related and are not even measured from the same points. Freebore starts at the end of the (typically) 45° bevel at the end of the chamber case mouth area and ends where it starts to taper from nominal groove diameter to bore diameter. That area is called the throat. The freebore can be referred to as the lead and is a straight section that's equal to or slightly larger than the bbl groove diameter. But once more, the lead and throat (freebore) are not even related to headspace in any way and are not measured from the same places. On top of that, the freebore will be the same length no matter how far the chamber reamer is run into the chamber. So it's impossible to change the freebore by altering the hs. I'm not sure I can put this any clearer than that.
OP, check or have the headspace set using a go and a no go guages. It doesn't get any easier than that and you'll need a go gauge to set the hs properly if it needs a small adjustment. Forget anything to do with your brass until you verify the hs is within the go and no go gauges!
When setting up your dies, that's when you'll measure a fired case with your comparator vs a sized piece of brass. Set the dies where the sized piece is .002-.003 shorter than the fired case. It's that simple. Notice I did not mention using a comparator to measure the hs gauge. That's because a comparator is not the way to measure anything. Rather, it's a COMPARE-A-TOR. It's only use is to compare two pieces of brass see how much shorter your sized brass is than your fired brass. They're only good at showing a difference but not an actual accurate measurement of anything.
I don't care what you've read or heard anywhere else. It was either wrong or you simply misunderstood what you read. Read my post slowly and without any preconceived notions about anything. Your life will get easier and you'll answer all of your questions related to this. The only way your freebore got longer was if a different reamer was used, with a longer freebore area, or it was throated longer in a separate step using a throating reamer. Still. it has zero to do with headspace, either way.
OP, check or have the headspace set using a go and a no go guages. It doesn't get any easier than that and you'll need a go gauge to set the hs properly if it needs a small adjustment. Forget anything to do with your brass until you verify the hs is within the go and no go gauges!
When setting up your dies, that's when you'll measure a fired case with your comparator vs a sized piece of brass. Set the dies where the sized piece is .002-.003 shorter than the fired case. It's that simple. Notice I did not mention using a comparator to measure the hs gauge. That's because a comparator is not the way to measure anything. Rather, it's a COMPARE-A-TOR. It's only use is to compare two pieces of brass see how much shorter your sized brass is than your fired brass. They're only good at showing a difference but not an actual accurate measurement of anything.
I don't care what you've read or heard anywhere else. It was either wrong or you simply misunderstood what you read. Read my post slowly and without any preconceived notions about anything. Your life will get easier and you'll answer all of your questions related to this. The only way your freebore got longer was if a different reamer was used, with a longer freebore area, or it was throated longer in a separate step using a throating reamer. Still. it has zero to do with headspace, either way.
Last edited:
