My Favorite "New Gadget" - Hornady Headspace Gauge

[EDG]

The name of this Hornady tool often starts arguments and snide comments from linguistic purists because it measures only cases and the purists always argue that cases don't have headspace- only the rifle chamber has headspace. That is fine but for me this is a very useful tool. With it I can measure the head to shoulder dimension of many bottle neck rounds. Indirectly the head to shoulder dimension of the chamber is transferred to the case when the round is fired. This allows you to set your FL sizing die. This is an outline of my use of the tool to date.

Hornady Headspace Gauge
http://www.hornady.com/store/Lock-N-...h-Body-1-Each/


A. Uses
You can check head to shoulder dimension to the nearest .001” of
Fired cases
Resized cases
Factory ammo - Some is very consistent, some is not so consistent
New brass - Same as factory ammo
Fired cases can give you the head to shoulder length of your bottle neck chamber

B. Use of the data
Check head to datum length of your bottle neck rifle chamber. Compare it to the SAAMI dimensions for maximum and minimum chambers. You will know your chamber headspace.
Check the head to datum length of factory ammo to compare it to your chamber.
Check the set up of your FL sizing die. Set the sizer to exactly match the length of your chamber down to the nearest .001 .
Understand and prevent case stretching and case head separation problems.
Greatly extend case life
Improve accuracy due to more consistent resizing
Understand the variations you produce in your sized cases that you did not know exist.

C. Understanding head to datum variations caused by the resizing process. Measure all cases that you size as you size them to understand the variables that affect the location of the shoulder. You will feel more or less effort on the handle of the press and the differences will show up when the case is measured.
The amount of lube on each case changes the friction and the location of the shoulder
Speed of the sizing stroke – eg how fast you stroke the press handle.
Dwell time at the top of the stroke - 3 to 4 second dwell at top of sizing stroke vs no dwell. Dwell gives the brass time to move and take a set.
Number of sizing cycles - Retract case 1/2”, spin case 180 degrees resize second time. Use dwell at top of both strokes. Or size 3 times with 3 dwells.

D. Other applications
Use as a substitute headspace gauge
Identify needed modifications to resizing dies – determine how much to face off of bottom of FL sizer
Modification of shell holders

One of my first uses of this tool was the forming of .303 British brass into 6.5X53R.
The 6.5X54 case is shorter than the .303 so it cannot be fit checked in the chamber until it is trimmed. Instead of trimming and checking I set up the file trim die using old once fired brass that had been trimmed. Once the trim die was set to give a light drag on the case I used the Hornady Headspace Gauge (HHG) to measure the head to shoulder lenght. That number was used as the acceptance number for sizing the rest of the new brass. With the cost of brass today I did not want to lose a single case. I got a 100% yield of good brass from that lot. After all the cases were sized, they were all trimmed about .100" and check in the rifle chamber. Each and every case provided very light drag when the bolt was closed. This will minimize the stretching of the cases when fired. These cases, when fired, maintained the same head to shoulder length.

[texassako]

Interesting little tool. It can even work with 7.62x39 Brit according to the chart.

[gpidaho]

Great little tool, have used them for years originally Stoney Point tool picked up by Hornady inserts for either work in Hornady or Stoney Point. GP

[JSnover]

Yeah, Stoney Point called theirs a bullet comparator. You used it to determine COAL for each boolit type.

[Doc Highwall]

Stoney Point had both the overall length and the headspace gage, I own both. Sinclair makes a version that has different shoulder angles for even more precise measurements as it contacts the whole shoulder angle not just a small diameter.

[EDG]

The SAAMI drawing specifications call for locating the shoulder datum with a basic ring diameter not a cone.
If as cone is used variations in the shoulder angle affect the actual measurement. If the edge of the guage diameter is deburred or broken you will get errors when you compare your brass measurements to the SAAMI chamber and cartridge drawings.

I just had an interesting experience. With .358 Win brass so expensive and hard to find I thought I would make some up for plinking. I scrounged some .308 brass.
I measured my fired .358 brass at 1.589 using the Hornady/Stoney Point tool.
I sized a case using my new old stock Pacific die and measured it at 1.595. With my RCBS FL die I got 1.587.
Brass fired in a longer chamber cannot be resized to fit my rifle using the Pacific die unless I cut about .006 to .007 off the base. It looks like the RCBS die is about perfect for my use. With a .002 deeper shell holder it would be right on the button.
Next task is to size a case right at 1.590 and see if it will chamber. If not then size it again at 1.589 and then 1.588. Then determine which is the best fit while permitting the low camming force bolt to open and close. Naturally this begs for another gadget - a set of the Redding shell holders with varying depths.

[Doc Highwall]

EDG, you are right about the gage point being a set diameter and also mentioned the edge break that could throw the measurement off.

For the people that are not familiar with head space, it is where a specified diameter at X.XXX dimension from the bolt face, the angle of the chamber +/- seconds of arc will touch, this angle is also on the cartridge case. What ever the actual head space of your chamber the case must be smaller/shorter.


Using the headspace gage lets you set your sizing dies up to your rifle chamber to push the shoulder back just enough to chamber without oversizing the brass not including the neck.

Reloading dies have a 7/8-14 thread pitch, 7/8ths diameter and 14 turns to a inch. This is .0714" per turn, let us round this to .072" to keep the math simple.

1 turn = .072"
1/2 turn = .018"
1/4 turn = .009"
1/8 turn= .0045"

as you can see it only takes a small amount of adjustment to change the headspace beyond optimum for long case life or accuracy.

[EDG]

7/8" = .875

.875 X PI (3.14) = 2.7475" around the OD of the thread

1 turn = .072 travel

To get the length of the arc for .001 adjustment

2.7475 / 72 = .038" Put a sharpy mark on top of your press next to the die body.
>>>>> = <<<<< The space between the bars of the equal sign are about .038
So rotate your die about that far for .001 adjustment.

[Doc Highwall]

EDG, I just divide 1 by the number of threads per inch to get the amount of travel per inch.

1" / 14 = .0714285" travel in one complete turn.
1" / 32 = .03125" travel in one complete turn..
1" / 40 = .025" travel in one complete turn.

Close enough for government work, not like I am sending a rocket into space and back.

[EDG]

Doc
I just added the .001 adjustment to give someone an idea of how small an increment it is on 14 threads per inch. It is about the same as the spacing of the .001 graduations for common inch mike.

[fguffey]

The name of this Hornady tool often starts arguments and snide comments from linguistic purists because it measures only cases and the purists always argue that cases don't have headspace- only the rifle chamber has headspace. That is fine but for me this is a very useful tool. With it I can measure the head to shoulder dimension of many bottle neck rounds. Indirectly the head to shoulder dimension of the chamber is transferred to the case when the round is fired. This allows you to set your FL sizing die. This is an outline of my use of the tool to date.

Linguistic. purest? I can not find a mention of case head space listed anywhere as it relates to SAAMI. Comparators and head space gages, twice I was asked to agree with manufacturers of comparators that were listed on the Internet as head space gages, rationale? I was advised the reloading world would be better served if I agreed with them. If I have to lend to a friend, friendship comes to high. A comparator is a comparator.

I make comparators, from the beginning I have insisted the tools are nice but not necessary. That was back when reloaders were under the impression the datum was a line, I insisted the line was one dimensional, the round hole circle/datum had three dimensions. Some reloading forums continue the drawing with the line on the shoulder and the arrow pointing to it. The arrow identifies the line as datum line, back to the start, the line is a round circle/hole.

It is good you have discovered the tool, for years all I have ever used is the circle/round hole drilled in a plate. The plate could be a wire gage, bolt diameter gage or drill index. All I have ever needed to understand is the datum, the datum is a round hole, SAAMI designators diameters. .375" and .400" are the common ones. My drills, my plates, my cases, I make up datums because I make comparators. I am not checking head space I am comparing an unfired minimum length case with a fired case then a sized case.

F. Guffey

[fguffey]

[INDENT]

[INDENT] The name of this Hornady tool often starts arguments and snide comments from linguistic purists because it measures only cases and the purists always argue that cases don't have headspace- only the rifle chamber has headspace. That is fine but for me this is a very useful tool. With it I can measure the head to shoulder dimension of many bottle neck rounds. Indirectly the head to shoulder dimension of the chamber is transferred to the case when the round is fired. This allows you to set your FL sizing die. This is an outline of my use of the tool to date.

Or: As an option the reloader can become a verifier, that being someone that verifies measurements. I could use 1/14th of an inch, I could use a height gage, I could use a depth gage or I could a use a dial caliper, instead I use the feeler gage, the verifying tool to verify measurements. Logic, if I am going to verify a measurement why not start with the verifying tool instead of the wild 'geuestimates'. Then there are shell holders from Redding, a 5 shell holder set in increments of .002" from +.002" to +.010", at $40.00 a set I have an option, I use the companion tool to the press, the feeler gage. Then there is the case that will not chamber after sizing, for me? Not a problem, I use the feeler gage to raise the case off the deck of the shell holder when forming short cases for short chamber or when the case is tougher to size that the press can overcome.

F. Guffey

[EDG]

>>>I am not checking head space I am comparing an unfired minimum length case with a fired case then a sized case.<<<

That is incorrect in the same way that I am not checking headspace.
You are not checking the case length, you are checking the case head to datum length (not called headspace on the SAAMI drawings) that corresponds with the functional dimension of the firearm chamber. That dimension on a bottle necked case is the functional dimension that is located by the bolt face datum and headspace datum in the firearm. The bolt face is the primary datum. The chamber shoulder is located relative to the bolt face.

If you do not want to call the head to shoulder length of a case a headspace dimension you are splitting hairs over language. That dimension is the functional dimension of the case controlled by the functional surfaces of the bolt face and the chamber shoulder.

The advantage of the caliper is its portability and ease of use.

Your simplistic explanation of measuring the case using a hole in a plate etc does not address verification that the hole is the basic diameter specified on the drawing. If the hole is not accurate in diameter then all you are doing is comparing one item with another. Your measurement is of no value if you try to compare it to the design drawing for the case.

[fguffey]

Your simplistic explanation of measuring the case using a hole in a plate etc does not address verification that the hole is the basic diameter specified on the drawing. If the hole is not accurate in diameter then all you are doing is comparing one item with another. Your measurement is of no value if you try to compare it to the design drawing for the case.

Then there are those that saw the dial caliper with attachments and could not match SAAMI specifications to there cases, chambers and new ammo. Then there were the ones that had an epiphany about the round hole. They went to the local hardware and purchased bushings with hole, the holes were rather limited to 3/4" without the .400" etc. They start with 'All I did was go to a hardware store and purchased bushing' without understanding the radius/bevel of the hole in the bushing. I have drills and reamers. Drill a hole then ream to specifications. I know, the sharp edge of the hole is not case friendly, but when I measure from the deck of the plate to the head of the case I know the length of the case from the datum to the head of the case.

Once a reloader in Canada contacted me to inform me he drilled the hole and said 'it works' but? I informed him there were improvements he could make after he understood the concept.

Then there is the L. E. Wilson case gage, for years reloaders used their thumb and vision, they were never able to appreciate the precision, not much has changed. In the beginning Wilson suggested using a straight edge, in those days who did not have a pocket rule? I use the straight edge and a feeler gage, I measured the gap between the straight edge and the gage to measure the length of the case, in thousandths, from the datum to the case head. I also stood the case on flat surface then placed the Wilson case gage over the case. After placing the gage over the case I measured the gap between the flat surface and gage to determine the length of the case in thousandths from the shoulder of the case to the head of the case. Then as now I thought Wilson was brilliant, other reloaders labeled the Wilson gage as a drop in gage, Wilson never labeled their case gage as a head space gage.

Measured from and datum, a reloader should not have difficult finding the bolt face, explaining to them how to find a datum just makes them mad and seems to make them wish they never learned to read. I am going to stick with the round hole in a flat surface/measure from as 'THE DATUM'. Everything is not a datum no more than everything has and is head space. I have no infatuation with head space.

F. Guffey

[EDG]

Actually the primary datum is the bolt face. The headspace datum is a secondary datum that is located from the bolt face.
If you wear our or change barrels the original datum, the bolt face, remains to locate the new datum in the new barrel.

I have a good number of the Wilson gauges and they have some utility but measuring is not one of them unless you have additional tools to go with them. They can be used as is for pass fail but they do not tell you the exact measurement. There is no dimension recorded on the Wilson tool allowing you to use them as a basis for recording an exact dimension. However if you have an indicator and stand, height micrometer and surface plate or a caliper and depth micrometer you can measure the guage. The functional guage length can then used to determine the length of the case.

Then there are those that saw the dial caliper with attachments and could not match SAAMI specifications to there cases, chambers and new ammo. Then there were the ones that had an epiphany about the round hole. They went to the local hardware and purchased bushings with hole, the holes were rather limited to 3/4" without the .400" etc. They start with 'All I did was go to a hardware store and purchased bushing' without understanding the radius/bevel of the hole in the bushing. I have drills and reamers. Drill a hole then ream to specifications. I know, the sharp edge of the hole is not case friendly, but when I measure from the deck of the plate to the head of the case I know the length of the case from the datum to the head of the case.

Once a reloader in Canada contacted me to inform me he drilled the hole and said 'it works' but? I informed him there were improvements he could make after he understood the concept.

Then there is the L. E. Wilson case gage, for years reloaders used their thumb and vision, they were never able to appreciate the precision, not much has changed. In the beginning Wilson suggested using a straight edge, in those days who did not have a pocket rule? I use the straight edge and a feeler gage, I measured the gap between the straight edge and the gage to measure the length of the case, in thousandths, from the datum to the case head. I also stood the case on flat surface then placed the Wilson case gage over the case. After placing the gage over the case I measured the gap between the flat surface and gage to determine the length of the case in thousandths from the shoulder of the case to the head of the case. Then as now I thought Wilson was brilliant, other reloaders labeled the Wilson gage as a drop in gage, Wilson never labeled their case gage as a head space gage.

Measured from and datum, a reloader should not have difficult finding the bolt face, explaining to them how to find a datum just makes them mad and seems to make them wish they never learned to read. I am going to stick with the round hole in a flat surface/measure from as 'THE DATUM'. Everything is not a datum no more than everything has and is head space. I have no infatuation with head space.

F. Guffey

[EDG]

If you measure the headspace with a caliper tool that is working correctly your numbers will match the SAAMI numbers unless your rifle chamber is out of tolerance. If you want to zero you caliper set up you can use an actual head space guage and zero the caliper assy based on the number on the headspace gauge. But instead of having a go, no go, or field pass-fail type gauge you can measure the exact dimension.

I got a new batch of 6MM Rem cases in a trade a few weeks ago. Some of the cases are new and some are once fired.
Out of curiosity I thought I would measure the cases and compare them to cases fired in my rifle. I found the fired cases were exactly the same head to shoulder length as cases fired in my rifle. The unfired cases were .002 shorter.
However I also decided to measure the shoulder diameter of my brass. The new unfired brass measured .425 in diameter at the shoulder. The fired cases in the new batch measured .436. Fired brass from my rifle measured .434. Based on this data it appeared the fired cases from the new batch would not chamber in my rifle. They didn't. The next task is to pull out some old cases and set up my FL sizer to resize the cases. I have 2 RCBS, 1 Forster, 1 Eagle FL sizers. I am going to measure the shoulder diameter produced by each of these dies and pick the one with the largest shoulder diameter smaller than .434.
There is another zig zag to make. I have another 6mm varmit weight rifle and brass. I need to measure brass fired in that rifle and compare it to the Hornady data. That is measure the actual head to datum length and measure the shoulder diameter. This data will be compared to the data for the hunting weight rifle. If the two chambers are significantly different I will have to set up a separate die for each rifle. If the two chambers are the same length I should be able to use a single die for both rifles.
This will be even more valuable data for 8X57 since I have several rifles for this cartridge. It will be interesting how much variation there is among rifles from 3 different factories.

[fguffey]

I have a good number of the Wilson gauges and they have some utility but measuring is not one of them unless you have additional tools to go with them.

I have additional tools, I have feeler gages and a straight edge. I also have a flat layout table, stand the case on the table, place the Wilson case gage over the case then measure the gap between the bottom of the gage and flat surface. The Wilson case gage is a datum based tool. My straight edge does not have a datum, my table does not have a datum.

F. Guffey