Experience w/ Hornady Headspace Comparator?

[Howland]

I'm just getting back into reloading but want to focus on autoloading. Most of my experience has been finding the best pistol rounds and cranking out volume, and fine tuning bolt action rounds, usually by neck sizing only. I don't have a whole lot of experience with bottleneck, autoloader cartridges and I'm hoping to tap into the knowledge of shooters/reloaders with more experience than myself in this area.

Now I have three .308s to load for, two of them autoloaders. I want to full length size but want to be able to measure, control and fine tune headspace.

I looked at the Hornady Headspace Comparator set and only see an extremely thin shelf to distinguish the headspace distance. Is this shelf measuring at the base of the neck or at the end of the case body? Is it suitable for measuring both fired and unfired cases? Is there a better/more accurate way to measure headspace?

 

[hogpatrol]

Wilson makes case gauges also.

 

[Texas10]

Here is another tool you might be interested in.

https://www.midwayusa.com/product/1012939524/rcbs-precision-mic

 

[retired]

you need to go look as SAAMI chamber/cartridge drawings.
the is a datum POINT on the shoulder of the case and a similar spot in the chamber.
you should probably shoot a bunch of the same lot of brass from all three guns and go from there.
mixed brass will give you mixed numbers.
i do not recommend your plan two if not all three guns will be shooting sub quality ammo.

 

[memilanuk]

There are a variety of ways to skin this particular cat.

I could spend a lot of time typing it all out, but instead, here are some links to more info on a few of them:

L.E. Wilson case gauge (same thing you already have)
Adjustable L.E. Wilson case gauge
L.E. Wilson adjustable depth micrometer (basically a purpose-built depth gauge just for this purpose)
Whidden case gauge (modern version of the old Mo's case gauge)
Hornady LnL Comparator kit (used to be Stoney Point; Whidden also makes a similar tool, as does Sinclair)

Originally I got started with RCBS Precision Mics... not really a fan. The dummy cartridge for seating depth is junk in my opinion; it bears no resemblance to the bullets I actually use so the information it provides is essentially useless (to me). At that point, it just becomes a headspace gauge... which it actually does fairly well. The Whidden case gauge is essentially the same thing, but *just* the case gauge, and arguably better made. Not too bad if you only load one or two cartridges, or ones from the same 'family' i.e. .243 Win / .260 Rem / 7-08 / .308, but if you load for a bunch of calibers and start buying them for each and ever cartridge (which RCBS will tell you is a 'must', because of their seating depth widget-thingy) the cost adds up FAST. At that point, the Hornady comparator kit becomes much more economical, because for the cost of basically one RCBS or Whidden case gauge, you get the ability to check headspace on *everything* you load from a .223 to a .308 to a .300WM, etc. The Sinclair set is supposed to be an improved version of the Hornady/Stoney Point design, in that instead of aluminum comparator inserts with a hole sized to match the headspace datum line for a cartridge group i.e. .400" for a .308, etc. they have a steel insert with a hole that is angled to match the shoulder angle of the particular cartridge you're using. Sounds 'better', but I ran into some problems where their idea of the correct angle for a cartridge apparently didn't match what was in my gun, and gave me some screwy readings - so I went back to the Hornady.

The thing to remember with some of these case gauges is that when you're measuring headspace, don't worry quite so much about some theoretical industry standard so much as what is in *your* gun. Bump back a few thousandths from fired dimensions to ensure your reloads will go back into *your* gun. How much varies a bit, whether you are shooting a match bolt gun (1-2 thou) or a off-the-rack semi-auto (3-4) thou. The directions that come with most F/L resizing dies are intended to make sure the ammo works in any and all guns in that caliber - i.e. make sure the biggest peg (cartridge) fits in the smallest possible hole (chamber). By necessity, that means you usually end up oversizing the cases if you follow the default setup instructions that come with your dies. Unfortunately, with your situation of multiple guns in one caliber, that might be where you end up. It's possible you can find a happy medium - bump the shoulder back enough to fit in *every* gun, but not quite as much as the factory die instructions say, and extend your brass life and increase accuracy a bit in the process.

 

[hrlincoln]

I looked at the Hornady Headspace Comparator set and only see an extremely thin shelf to distinguish the headspace distance. Is this shelf measuring at the base of the neck or at the end of the case body? Is it suitable for measuring both fired and unfired cases? Is there a better/more accurate way to measure headspace?

Not sure what you mean by 'shelf'...the comparator's inside edge measures to the corresponding OD on the case's shoulder. Its intended purpose is exactly that...to measure/compare 'base to shoulder' dimensions of unfired, fired, and re-sized brass. The Hornady has served me well for many years but there are alternatives.

 

[Howland]

you need to go look as SAAMI chamber/cartridge drawings.
the is a datum POINT on the shoulder of the case and a similar spot in the chamber.

Got it. After going straight to the source, SAAMI defines the headspace as the midpoint between the base of the neck and the shoulder, both of which are simply reference points. The Hornady #10 only showed the dimension of the base of the neck to the base of the case.

youshould probably shoot a bunch of the same lot of brass from all three guns and go from there.

That is exactly my plan and I'll consider your recommendation as a ringing endorsement.

ido not recommend your plan two if not all three guns will be shooting sub quality ammo.

I might have been a bit imprecise. I need to be able to measure the three different headspace dimensions so I know what the differences are. If any two of the three are identical, it would either be like winning the lottery or a testimonial to industry uniformity and the capability to adhere to tight manufacturing tolerances. As a famous American once said, "Trust but verify."

In total, your advice appears to be an affirmation of my instincts. I thank you for taking the time to steer me away from trouble. It's exactly why I joined this site.

 

[Howland]

The consensus appears to be that despite the Hornady gauge measuring to the shoulder instead of the SAAMI defined headspace, those using the Hornady find that it is indeed a useful and consistent tool to measure the "headspace" (sort of, more precisely the shoulder) of each chamber to the corresponding point of both fired and sized cases.

I'm going to check out some of the other tools suggested before pulling the trigger, but I thank all of you for your suggestions.

 

[Metal God]

I've used the Hornady headspace gauge with great success . I feel it's important to understand that it's a "comparator" and is not designed to give the actual measurement . Mine "measures" a 308 GO-gauge .010 short . How ever when "comparing" your fired cases to your sized cases it works great IMO .

I found the Sinclair inserts for comparing bullets to work better then the Hornady ones . They are truer to the ogive diameter and there contact point has a harper radius . On the other had the Sinclair headspace inserts work completely different then the Hornady inserts . I bought some and all they did was confuse me . They did not even come close to measuring the GO gauges correctly and when comparing the measurements each different insert gave ( Hornady or Sinclair ) the numbers were all over the map . The Sinclair's may work but I think I had been using the Hornady for so long my brain could not transition to the new method , what ever that is .

 

[jimbires]

I was helping a new reloader about a year ago with this hornady tool . he seemed to be having trouble grasping the fired case length compared to the resized length . after watching him for a short time, I measured a fired case , and set the caliper to zero . then when a sized case is measured it shows how far you bumped the shoulder . he had this method locked in right away .

 

[WEL]

I use the Hornady. It is a comparator not a true headspace measurement but that's ok. I would take some brass fired in each rifle keep them seperate and measure to see how close they are. If you get Lucky and they are within say .003,.004 of each other then you can size all your brass to set back the smallest measurement by 2-3 thou and be gtg. This is not likely to happen and you may need to keep brass segregated per chamber.

 

[jsn]

The only way to know the true headspace of your chambers is to find someone with a set of .308 Match Headspace Gauges. Those were $300+ the last time I checked into them.

The comparator is an acceptable way of measuring what comes out of your rifles. I use it. The radius on the comparator was measured to be a .009" offset from the actual gauge on my bushings. The semi-autos may need to have the gas systems disconnected in order to shoot them single shot like a bolt action, otherwise the brass may stretch too inconsistently to get useful measurements.

 

[ireload2]

The Hornady tool is a very good comparator.
The datum edge of the Hornady bushings have been broken or deburred. The edge break causes the gage to read a shorter dimension than what is real.
If you set the Hornady gage to match the size marked on a gunsmith headspace gage you will be able to measure your cases in real dimensions.
I have used this tool about 15 years and I am pretty happy with its use.
Using this tool I have developed a FL sizing process that will produce long runs of formed cases that are exactly the same length and are an exact fit for even 100 year old chambers.

 

[MSS]

I also use the Hornady Headspace Comp and it works well. Whidden also has a nice shoulder bump gauge that people like. It is caliber specific though whereas the Hornady has inserts that you can swap out for different calibers.

 

[Ron Blain]

The Hornady tool is a very good comparator.
The datum edge of the Hornady bushings have been broken or deburred. The edge break causes the gage to read a shorter dimension than what is real.
If you set the Hornady gage to match the size marked on a gunsmith headspace gage you will be able to measure your cases in real dimensions.
I have used this tool about 15 years and I am pretty happy with its use.
Using this tool I have developed a FL sizing process that will produce long runs of formed cases that are exactly the same length and are an exact fit for even 100 year old chambers.

I use the Hornady tool as well as the RCBS Precisioon Mic. Now that said and before half the forum membership comes down on me I agree that if we read the SAAMI Glossary it will state the following:

HEADSPACE: The distance from the face of the closed breech of a firearm to the surface in the chamber on which the cartridge case seats.
HEADSPACE GAGE: A device used in a firearm to determine the distance between the breech face and the chamber surface on which the cartridge seats. Also called Breeching Plug.

So the argument becomes that a cartridge does not have a headspace dimension. Using the .308 Winchester cartridge as just an example and referring to the actual SAAMI drawings here is what we get:

The above drawing reflects both the cartridge (top) and chamber (bottom) dimensions. Worth noting is that only the bottom chamber drawing reflects a headspace dimension. This is why many shooters and avid hand loaders will make the statement that cartridges don't have a headspace dimension. With that said and understood if we do a simple Google of we see The Hornady Lock-N-Load® Headspace Comparator & Anvil Base Kit. Along with a plethora of other countless gauges for use with a cartridge. Personally rather than swim against the currents or fly into a headwind I just refer to such gauges as cartridge headspace gauges and be done with it. The guys making and marketing the things choose to call it a headspace gauge so who am I to argue?

That said the gauge itself may best be viewed as a comparator. Take a before and after measurement and do the math noting the change. As mentioned the Hornady gauge Anvil Kit uses anvils which where they meet the case have a slight radius and not a sharp corner break. They are also made of aluminum alloy and not steel. Looking at the above chamber drawing the datum point on a .308 Winchester is where the shoulder diameter crosses the 0.400" point. Using the Hornady gauge set this would be the D 400 Anvil. Using an ID micrometer and measuring the ID it is in fact 0.400" however there is a radius and not a sharp corner break. So just to get to the truth of the matter we can measure. as was mentioned, an actual chamber headspace gauge.

The gauges on the right are actual chamber headspace gauges. Using a precision 1.630" headspace gauge here is what happens:

Now we measure a known true 1.630" .308 Winchester headspace gauge:

We see the gauge is measuring right at 0.006" low and this runs with exactly what ireload2 states when he mentions:

The Hornady tool is a very good comparator.
The datum edge of the Hornady bushings have been broken or deburred. The edge break causes the gage to read a shorter dimension than what is real.
If you set the Hornady gage to match the size marked on a gunsmith headspace gage you will be able to measure your cases in real dimensions.

The question is does it matter and I do not see where it matters. When cutting a chamber one uses a chamber headspace gauge but when measuring a fired case all one cares about is resizing the case and by how much. The below is brand new Federal Gold Medal Match ammunition.

Because I know the error of my gauge I can add 0.006"and know my pre fired case is 1.629" case head to datum. So now I fire my cartridge and measure again.

Using that 1.627" as my reference all I need to do is adjust my resizing die till I see a number around 1.625" and pretty much figure I have bumped my shoulder back 0.002" and be happy. We can reserve "bumping the shoulder back" arguments for another day.

Ron

 

[retired]

that is a DIGITAL caliper, NOT A VERNIER. a vernier would have marking on the length ..not a read out.

I use the Hornady tool as well as the RCBS Precisioon Mic. Now that said and before half the forum membership comes down on me I agree that if we read the SAAMI Glossary it will state the following:

HEADSPACE: The distance from the face of the closed breech of a firearm to the surface in the chamber on which the cartridge case seats.
HEADSPACE GAGE: A device used in a firearm to determine the distance between the breech face and the chamber surface on which the cartridge seats. Also called Breeching Plug.

So the argument becomes that a cartridge does not have a headspace dimension. Using the .308 Winchester cartridge as just an example and referring to the actual SAAMI drawings here is what we get:

The above drawing reflects both the cartridge (top) and chamber (bottom) dimensions. Worth noting is that only the bottom chamber drawing reflects a headspace dimension. This is why many shooters and avid hand loaders will make the statement that cartridges don't have a headspace dimension. With that said and understood if we do a simple Google of we see The Hornady Lock-N-Load® Headspace Comparator & Anvil Base Kit. Along with a plethora of other countless gauges for use with a cartridge. Personally rather than swim against the currents or fly into a headwind I just refer to such gauges as cartridge headspace gauges and be done with it. The guys making and marketing the things choose to call it a headspace gauge so who am I to argue?

That said the gauge itself may best be viewed as a comparator. Take a before and after measurement and do the math noting the change. As mentioned the Hornady gauge Anvil Kit uses anvils which where they meet the case have a slight radius and not a sharp corner break. They are also made of aluminum alloy and not steel. Looking at the above chamber drawing the datum point on a .308 Winchester is where the shoulder diameter crosses the 0.400" point. Using the Hornady gauge set this would be the D 400 Anvil. Using an ID micrometer and measuring the ID it is in fact 0.400" however there is a radius and not a sharp corner break. So just to get to the truth of the matter we can measure. as was mentioned, an actual chamber headspace gauge.

The gauges on the right are actual chamber headspace gauges. Using a precision 1.630" headspace gauge here is what happens:

Now we measure a known true 1.630" .308 Winchester headspace gauge:

We see the gauge is measuring right at 0.006" low and this runs with exactly what ireload2 states when he mentions:



The question is does it matter and I do not see where it matters. When cutting a chamber one uses a chamber headspace gauge but when measuring a fired case all one cares about is resizing the case and by how much. The below is brand new Federal Gold Medal Match ammunition.

Because I know the error of my gauge I can add 0.006"and know my pre fired case is 1.629" case head to datum. So now I fire my cartridge and measure again.

Using that 1.627" as my reference all I need to do is adjust my resizing die till I see a number around 1.625" and pretty much figure I have bumped my shoulder back 0.002" and be happy. We can reserve "bumping the shoulder back" arguments for another day.

Ron

 

[BoydAllen]

I have used the gauge that is now sold by Hornady for couple of decades. I got the identical unit when they first came out and were sold under the Stoney Point brand. As long as you keep in mind that this tool is not a headspace gauge but rather a comparator, designed to aid in the accurate setting of FL dies you should be fine. If you are curious you can purchase a GO gauge and compare your case measurements to that, but your actual die settings should be in relation to fired cases. I use mine all of the time and find it to be very handy, I use a dial caliper and never bother to set it to zero with the tool installed since I am only interested in the difference between two measurements. As long as the caliper is set the same for both the absolute numbers are irrelevant. Be sure to either remove the primer from your fired case or re seat it with a priming tool so that it is well below the case head before taking a measurement.

 

[Ron Blain]

that is a DIGITAL caliper, NOT A VERNIER. a vernier would have marking on the length ..not a read out.

My bad and absolutely it is a digital caliper.

Thank You
Ron

 

[Brer Rabbit]

Thank you Ron for an excellent explanation of the use of the comparator.

BR

 

[M-61]

comparator:
any of various instruments for making comparisons, as of lengths or distances, tints of colors, etc.
From the definition it is really what I am doing. COMPARING my resized brass to fired (in my chamber) brass. I don't look at or try to match SAAMI numbers as it's not my chamber their measuring nor my fired brass.