Am I lookin at this correctly?

[hangunnr]

Been shooting the B14R heavy and just finally got around to measuring headspace.
Made up a simple tool to measure rim thickness. It’s just a piece of round aluminum stock with a .228” hole. It fits perfectly in the Stoney Point adapter.

After installing on my caliper and zeroing I used a fired case to produce the measurement shown. Am I correct in thinking this is showing a .046 headspace?

Here is a unfired SKRM.

That would indicate .004 “slop” in the headspace, correct?
I see quite a few reference .043 as a good headspace measurement so if I shim the bolt .003 it should put me in a sweet spot.

 

[RTH1800]

I am not a machinist but I do know that brass has a degree of "pull back" so the number you are seeing is not likely to be accurate.
Headspace is not measured by fired rim thickness. It is measured with hardened tool steel gauges. You can buy or make them. If you choose to make them I suggest you do it on a no go process. Make one .047 and cut it back .001 until the bolt closes on it.
Unless you have a lot of time or are short of cash I suggest you just buy a set.
I looked and Whidden gun works has a .039 to .045 set for 75.00. A set going from .039-.052 is 140.00. I am sure there are many other vendors as well.

 

[Magspring]

If you are wanting a very specific headspace the Whidden set works well.

 

[hangunnr]

The brass spring back / pull back is something I hadn’t considered. Good thought!
So not being one to give up and just throw money at it I tried this…..
Took 5 fired cases and annealed the head then a punch with rounded tip to ballon it out a bit.

All five were then run thru the chamber and I got a measurement of .047 on all five.

Is this as good as the “proper” tool……I don’t know.
It will however satiate a curiosity. I have a shim kit for the bolt inbound so we’ll see if that and sorting the ammo by rim thickness shows on the target.

 

[Hi-NV Shooter]

The brass spring back / pull back is something I hadn’t considered. Good thought!
So not being one to give up and just throw money at it I tried this…..
Took 5 fired cases and annealed the head then a punch with rounded tip to ballon it out a bit.

All five were then run thru the chamber and I got a measurement of .047 on all five.

Is this as good as the “proper” tool……I don’t know.
It will however satiate a curiosity. I have a shim kit for the bolt inbound so we’ll see if that and sorting the ammo by rim thickness shows on the target.

Only legible area to measure is the OAL from the front of the case rim to the Ogive or first driving band. like CF jam how much the bullet engages the leade will have an effect. the late Bill Calfee who built some of the most winningest RFBR rifles always believed that AOL of the lot was more important than the speed.

Lee