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Case Gauge FYI

Discussion in 'Handloading and Reloading' started by tcoz, May 30, 2017.

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  1. tcoz

    tcoz Member

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    Case gauges are often talked about and recommended on the various reloading forums so I want to make sure that everybody, especially new reloaders understand something about them.
    The majority of well known gauges (Wilson, Lyman etc) are not made with a chamber reamer and they don't gauge cartridge diameter so just because your finished cartridge passes the gauge test doesn't mean it will chamber in your rifle. These gauges are used only to check case headspace against SAAMI minimum & maximum to help you adjust/set up your sizing die and to check case length for trimming purposes.

    On the other hand there are a few gauges such as JP Enterprises, Sheridan and a few others that I can't remember right now which are cut with a chamber reamer to minimum SAAMI dimensions. In addition to verifying headspace and checking case length they can be used as a final check for your finished rounds. If the round passes the gauge test, its guaranteed to chamber in your rifle. The converse is not necessarily true however. If a round fails the gauge, it may still chamber in your rifle depending on the size of your rifle's chamber.

    Before buying a case gauge, decide which one will best fit your needs. Also, the Sheridan gauge comes in a slotted version that lets you see the case/cartridge in the gauge and will help to diagnose chambering and die setup problems.
     
  2. Jesse Heywood

    Jesse Heywood Member

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    The slotted Sheridan gauges are nice. Made so you can see where the round doesn't pass. They are still a mom & pop store so you get great service. We are trying to get enough people to request 22TCM gauges for a run.
    www.zepprecisionmachines.com
     
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  3. Toprudder

    Toprudder Member

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    Also, most straight-walled case gauges for pistol rounds only check the dimensions of the brass case. They do NOT perform the equivalent of a plunk test, in other words they do not simulate the leade or freebore of the barrel in front of the case mouth.

    There is at least one manufacturer of pistol case gauges that advertises they use a Clymer chamber reamer, which would simulate a gun barrel, but it won't necessarily match any particular gun.
     
  4. jmorris

    jmorris Member

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    FWIW the round in a slotted gauge can have an imperfection in the cut away portion and pass, even if it were clocked differently and fail.

    If you want a perfect case gauge, when you (or your gunsmith) cut your barrel to length take the drop and use the same reamer you chambered the barrel with. It will be as perfect as you can get, including lead.

    A "plunk" test checks little if any of the base of the case, where extractor/ejector dents and dings can cause issues entering a breech face for example.
     
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  5. Nature Boy

    Nature Boy Member

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    Case gage > nothing

    I use them as a reference but rely more on my Hornady headspace comparator for setting up dies to get the desired shoulder bump for my bolt actions.

    Having recently made my first baby steps into pistol reloading I found the 9mm Dillon case gauge to be very handy. Had a couple of cases that were a bit "sticky" and did a plunk test with my pistol. They were sticky in the chamber as well. Again, I find them to be a handy reference.
     
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  6. tcoz

    tcoz Member

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    Like you, I also use the Hornady Headspace Comparator which has the added benefit of using relatively inexpensive bullet bushings to measure base to ogive measurements for more accurate seating depths.

    Another tool which I use and I find is faster and more accurate for headspace measurements is the RCBS Precision Mic. It's more expensive and you need a different one for each caliber but it's easier to manipulate and get an accurate reading. It also has the advantage of giving you a headspace reading that is a direct comparison to the SAAMI minimum headspace dimension. As I mentioned in another post, the aluminum bushings in the Hornady comparator can get out of spec pretty easily and you also have the inherent error in setting the case into the tool just right as well as the error in your calipers so you don't ever want to use it to arrive at a hard number, only for a comparison to another cartridge that you can measure in the same tool.

    For example, if you know your rifle is headspaced at 1.632", don't use the Hornady gauge to set your sizing die to get a shoulder setback to 1.630". In my case, it was measuring .007" short which could lead to a dangerous situation. If, on the other hand, you can compare the measurement against a fired case it'll be accurate but in the M14/M1A for example, the case continues to expand slightly after extraction so a fired case isn't an exact measurement of your chamber dimensions. If you want to test the accuracy of the Hornady tool and you have a go-gauge, measure it in the comparator. I can almost guarantee you won't get an accurate measurement of the gauge. I've tested each Precision Mic that I own against a go-gauge and found every one to be spot on.

    Both tools have their place but you should assess your needs before buying or if you're a reloading tool geek like me, buy them both.
     
  7. RussellC

    RussellC Member

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    Correct, I have several for the rifle calibers I load for, Sheridan and Wilson included. As you say, Wilson isn't a true chamber, but I like it in combination with their depth gauge micrometer. I have never had a round that passed the Wilson that did not chamber, however. Not yet.

    Russellc
     
  8. Reloadron
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    Reloadron Contributing Member

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    These threads always make for some good and helpful information getting out. The Wilson Case Gauge Instructions are pretty clear on what their gauge will and will not do. The following holds true for Wilson and similar case gauges, Forster comes to mind. From our friends at L.E. Wilson:
    These gauges do not check case diameter but the new guys out there are making gauges cut using a chamber reamer, Sheridan which has been mentioned comes to mind.

    As a matter of importance I believe the new hand loader or the old hand loader should look carefully at what each gauge does and more importantly does not do. This is the only way to make a well informed decision on which gauge to buy for their specific needs. I saw some mention of the Hornady Lock-N-Load Headspace Gauge 5 Bushing Set with Comparator. I also saw what others using this gauge set have noticed. The gauge can be used as a comparator but as to measuring a case headspace (or what we call case headspace) the gauge won't do it. Here is an example of what I am getting at and what was mentioned.
    [​IMG]

    The gauge was correctly zeroed and a known 1.630 actual headspace gauge is being measured. Note the 1.624 reading. The gauge is reading 0.006" below what it should. The actual headspace gauge is a .308 Winchester gauge also suitable for 243 Winchester. The problem is the radius where the case sits on the shoulder. Can't help but think stainless steel would have been a better choice but would have added cost and machining. The gauge will serve as a comparator which is what they advertise. Measure a fired case size till you get the desired number moving the shoulder back.

    Finally while the term "headspace gauge" is used for cartridges and become commonly used and accepted a headspace gauge is actually the gauge inserted into the Hornady Comparator above. The term cartridge headspace has become so commonly used it is pretty much understood what is being communicated. All of that aside when buying a gauge know what you are buying and what features it will measure. While more expensive I like the RCBS Precision Mic sets and have found the ones I used to always be within +/- 0.002 worst case with most nominal or close enough.

    Ron
     
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  9. RussellC

    RussellC Member

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    Yep, I have the Sheridan and Hornady Comparator as well. Also the RCBS precision micrometer as well. Sort of a tool junkie.


    Russellc
     
  10. RussellC

    RussellC Member

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    Using the headspace gauge as a starting point for measurement has this problem: This method assumes the chamber is the same as the gauge, which is not always the case. I use the comparator to measure my fired brass after shooting, and then it will show how much I am bumping the shoulder back on resize. If your chamber is slightly larger than SAMI, the measurement now isn't accurate as to how much shoulder is bumped when compared to just a go gauge...The RCBS precision device you mention has a tool with it that is adjustable length, sort of looks like a bullet. This item can be used to determine your particular chamber's peculiarities.

    Russellc
     
    Last edited: Jun 1, 2017
  11. RussellC

    RussellC Member

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    I have not succesfully used the device included with the RCBS unit, in the AR15 I first tried to use it with, it kept varying length and I gave up on it. I will try it again and report back, but I think it was more intended for a bolt action. Maybe if I close the bolt slowly?

    Russellc
     
    Last edited: Jun 1, 2017
  12. Reloadron
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    Reloadron Contributing Member

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    The key word is slowly and combine that with gentle. I have only used the tool in bolt guns and then with stripped bolts but slowly and setting the tool friction tight helps. If I were to use the tool in any of my AR rifles I would likely strip the bolt and then try the tool.

    Ron
     
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  13. tcoz

    tcoz Member

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  14. tcoz

    tcoz Member

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    No matter what I did I couldnt get a consistently accurate reading with it so i finally went with the Hornady OAL gauge which works extremely well for me.
     
  15. Reloadron
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    Reloadron Contributing Member

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    You're not alone on that. I generally start a bullet and let the bolt seat it and then use the gauge to measure that case with that particular bullet and label it. Never had the best of luck with their plastic nylon bullet affair (tool). :) I do very much like the case gauge though. That works very well.

    Ron
     
  16. tcoz

    tcoz Member

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    I dont know why the precision mic isnt more well known than it is. Its really a great tool and doesnt suffer from the same wear, soft metal and user error issues that the Hornady tool does. But that nylon bullet thingie really does have to go.
     
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  17. Reloadron
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    Reloadron Contributing Member

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    I figure it is cost. The RCBS Precision Mic isn't cheap and you buy by caliber where other tools are one size fits all and people seem to want the inexpensive stuff. Anyway, I like the precision mic sets but yeah, the tool for working out bullet jump leaves a lot to be desired. :)

    Ron
     
  18. RussellC

    RussellC Member

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    By stripped, do you mean no gas rings, firing pin, cotter pin, extractor, ejector or cam?

    Russellc
     
  19. Reloadron
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    Reloadron Contributing Member

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    No firing pin. extractor or ejector.

    Ron
     
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  20. RussellC

    RussellC Member

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    Thanks, I will try it that way.

    Russellc
     
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