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

 

[RTH1800]

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.

A lot of times people are willing to help on this site.
None of us can help those who refuse to help themselves.

 

[bostonbullit]

I have seen the anneal and punch method suggested around the interweb and it'll probaby get you somewhere close. Given that we're dealing with .001" here, depending on your goals somewhere close may or may not be good enough. I was troubleshooting headspace on a "pre-fit" bergara barrel and went through a few diff methods before just getting the Whidden gauge set. Since you already made a rim thickness gauge I suggest gauging the thickness of a case and then adding a layer of scotch tape to it. Keep doing that until you notice a diff in closing the bolt and then gauge it again. For me that was the best way of doing it before I got the Whiddens.

 

[hangunnr]

Would have tried the tape method first but don’t have any here.
Ran another 10 thru this morning and had 9/10 come back with the .047 measurement. I’d guess I didn’t get enough heat into the head of the 10th. After the shims get here and their actual measurement is verified I’ll run another 10 cases thru to verify their function.

This thread was put up in question form to get feedback to hopefully work the errors out of the process. The brass spring back was an issue and it was easily surpassed. If there are other problems with this system please feel free to address them. If passive aggressive insults are all that are left that’s ok too….

Measurement of the cartridge from the front of the rim to the ojive/driving band is something I’ve not heard of before. Can you elaborate on that. I’d like to see the tooling required.

 

[smelv]

G'day hangunnr,i have 3 benchrest guns.Two are set up for eley match/bolts will close on . 043 and will not close on .044 thou. Third is set up to shoot lapua centrex and will close on .044 and will not close on .045 thou as the rim thickness is .040. Eley is .038. I have made a set of guages by superglueing brass / copper /aluminium shim on the end of cases. I batch all my ammo by ogive length.I got a case of eley 1023-06214 last year and batched 17 boxes.13 boxes went .759 /.760 ogive length. 2 boxes were .751/52 and 2 were .753/54.The tool i use is just a case belled on the end to fit over the lead to just touch the ridge.I used the shank of a drill bit. The hole in the case is so i get it in the same place every time . Scott in Australia.

 

[hangunnr]

Nice, simple and effective.
Got to thinking about how to mount the fired case to the caliper and came up with this. The arthritis in my fingers make holding small objects challenging at times.

It uses the 24 cal bushing from the Hornady ogive measuring kit. The washer and spring is just to hold the case in place.

 

[EagleEyeShooting]

Two ways to get correct headspace on traditional interference fitment 22lr actions (Using extractors that grab around the case rim) from most accurate to least accurate and a method to see if your rifle is over headspaced to your ammo

Depth Micrometer:
1.) Direct measurement of bolt head to bolt face then compare to tennon length. Subtract Tennon Length of the barrel from the measurement from top of the action to bolt head

Precision Ground field gauges:
2.) Specific field (go gauges) with set measurements to find when your bolt closes with slight resistance. Many recommend the Whidden gauges, but I have had 4 sets of those and found them off +- 0.0015 -0.0025 off. I recommend ones precision ground from JGS Precision

Case Rim Thickness and Scotch tape as a No Go Gauge:
Using your comparator, measure a case rim of a cartridge for baseline measurement. Adding a piece of clear scotch tape will add an additional 0.006'' cut around the case rim with a razor. If your bolt locks down with 1 piece of tape, this will give you a general idea of your rifle setup is over headspaced to the ammo your shooting

 

[6.5SH]

G'day hangunnr,i have 3 benchrest guns.Two are set up for eley match/bolts will close on . 043 and will not close on .044 thou. Third is set up to shoot lapua centrex and will close on .044 and will not close on .045 thou as the rim thickness is .040. Eley is .038. I have made a set of guages by superglueing brass / copper /aluminium shim on the end of cases. I batch all my ammo by ogive length.I got a case of eley 1023-06214 last year and batched 17 boxes.13 boxes went .759 /.760 ogive length. 2 boxes were .751/52 and 2 were .753/54.The tool i use is just a case belled on the end to fit over the lead to just touch the ridge.I used the shank of a drill bit. The hole in the case is so i get it in the same place every time . Scott in Australia.View attachment 8786184View attachment 8786185

Nice, simple and effective.
Got to thinking about how to mount the fired case to the caliper and came up with this. The arthritis in my fingers make holding small objects challenging at times.

It uses the 24 cal bushing from the Hornady ogive measuring kit. The washer and spring is just to hold the case in place.

I applaud both of you for your creativity. Will be giving this a try.

I tried to get DI to make something similar to the old G3 Mk II tool:

https://bulletin.accurateshooter.com/2013/02/g3-rimfire-rim-thickness-tool-and-base-to-ogive-length-gauge/