6mm arc, headspace gauge issues, oversized chamber?

It's a comparator, so measurements are relative, such as when comparing fired cases to resized ones. In that situation, the before and after numbers on the caliper are just subtracted to learn their differences, which is how far the shoulder has been extruded down toward the head.

Other kinds of spacers can be used, but that flanged bearing journal is easy to keep in place with your fingers. Ideally, the hole through the bushing would be identical to the shoulder datum diameter in the SAAMI drawing, but because you are comparing rather than making absolute measurements, it doesn't have to be that exact. If you want to know how it compares to true minimum headspace, put a headspace GO gauge in.
 
Unclenick said:
It's a comparator, so measurements are relative, such as when comparing fired cases to resized ones. In that situation, the before and after numbers on the caliper are just subtracted to learn their differences, which is how far the shoulder has been extruded down toward the head.

Other kinds of spacers can be used, but that flanged bearing journal is easy to keep in place with your fingers. Ideally, the hole through the bushing would be identical to the shoulder datum diameter in the SAAMI drawing, but because you are comparing rather than making absolute measurements, it doesn't have to be that exact. If you want to know how it compares to true minimum headspace, put a headspace GO gauge in.
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Thats an excellent idea! I will test with my go/no-go gauge!
 
Phew, this is making my head hurt and having two teeth pulled is bad enough!

TMI can confuse things.

I am pretty basic. I measure my fired brass for where the shoulder is (and what you use to get that is not important, its what happens in the die and how much the shoulder moves back)

So, if it measure 2.155 I aim for 2.150. I know that is more than most but be it me or what, I find an occasional case that is a tight close if I do less. I don't care to measure each and every case either before or after.

But the reality is you fire form to the chamber you have, not some ideal. And yes Chamber gauges are important if you build your own guns (aka Savage pre made barrels as well a Remage and some others now)

If you really want to know, take your brand new brass (be it already loaded or the non loaded) and see if it goes into the chamber easily (any gun but also a great check for a barrel you have put on)

If new brass or a new loaded case goes in, lovely. It should of course.

Then you put something in the case or fire the factory ammo and you have fire formed to your chamber and can measure where that put the shoulder.

Move it back .003 (or in my case .005) and see if that round fits the chamber nicely. If it does, you don't need to look further.

If it does not fit then you have a small chamber that the die can't resize as it should more than slide in easily after a .005 shoulder push back.

I try to keep my end simple. Its all my brain can handle. With my built rifles I can shoot 1/2 MOA (assuming its a good barrel, some are great, some are good and some suck)

For the sort of serious target shooter that is not into competition that is good enough and the occasional 1/4 MOA group is fun.
 
Ok, got fired rounds. Headspace comparator gage measures on 3rnds were identical.

Fired 1.192
Factory new 1.184
Resized, hornady die 1.183

So it seems growth is about 0.008 to .009 not terrible really.

Im going to try and adjust my die to get about 0.003 to 0.004 bump since its a semi auto.

Spec on the shoulder to body junction is 0.430, im coming in at 0.432

Think the chamber might be a touch wide.

Will be sending some fired brass, and the gage back to l.e. wilson to get looked at later this week.
 
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Head clearance of 0.008” to 0.009” is quite a bit for a high power rifle. It is weird. The factory round must meet saami specs. The chamber passes no-go. Something among these three must be wrong; the factoy round, the rifle chamber, or the gauge.

Well it doesn't matter if you plan to fire handload only, rounds that are sized to fit this chamber.

-TL

Sent from my SM-N960U using Tapatalk
 
I'm leaning towards the chamber.

1 L.E. wilson is a reputable tool and gage maker, and their gage is intended, per their instructions, to accept fired brass. And it will not accept fired brass from my rifle.

2 I used hornady dies to resize my brass and with a full resize (light cam over against the shell plate) they were within 0.001 of the loaded factory ammo making me think both are within spec as the dies match the factory ammo.

I am hoping L.E. Wilson will answer this riddle. Sending the Gage and some fired brass to them. If they verify the gage is in spec, and the brass is over size that will answer it.
 
I reread some of the older posts. The headspace spec max is 1.190”. Your fired brass is 1.192”. That's after the brass has sprung back after firing, mind you. The actual chamber headspace is more than that. Sounds like your chamber was indeed cut long. But didn't you say it didn't close on no-go? That part is suspicious. Something not right about that no-go gauge.

I guess the chamber was cut about 0.004" over spec. If it is an option, I'd have the barrel set back by 0.007", which is about double of a printer paper thickness. If not, I just keep shooting handloads that are sized to fit this chamber, till I need to set back to shorten the eroded throat.

-TL



Sent from my SM-N960U using Tapatalk
 
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