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Thread: Very Confused - Bullet Comparators

  1. #1
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    Sep 2008
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    Very Confused - Bullet Comparators

    I am acquiring reloading equipment (never reloaded before), and am struggling to understand bullet comparators and how they are used. This is one of those things for which a video would be a huge help.

    If I understand the process, one uses the Hornandy OAL tool with the proper Hornandy special case and your bullet to determine the distance from the cartridge base to the bullet ogive. Then, one afixes a device that appears to be part of the bullet comparator to a caliper blade. Inside this sits an insert for the caliber bullet you have. Close the calipers down and reset to zero. Then open up the calipers and insert a completed cartridge, with bullet nose into the aforementioned insert, and the other caliper blade against the base of the cartridge. If you wanted the bullet .010" off the lands, you would want your live round to have a dimension .010" shorter than the case measured by the Hornandy OAL device. Do I have this right?

    Has anyone used the Sinclair Seating Depth tool, a competitor to the Hornandy OAL device? See here for comparison.

    http://blog.sinclairintl.com/2009/03...seating-depth/

    Given I have never used these devices, would appreciate any corrections on my understanding of these things work or recommendations.

    Thank you.

    - Phil

  2. #2
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    For the most part, thats basically true. I see no need to close the calipers
    down and reset to zero. The calipers should be checked and or adjusted
    when ever you pick them up. Measuring Loaded length with the inserts
    gives you a dimension which is relative to your gun/bullet/ lands contact.
    Should you want it less , shorten it by that amount. The big problem is
    finding the bullet lands contact dimension to start with. Each method of
    doing this is not a precise as many of us want, but its a number
    that is a starting point.

  3. #3
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    The most straight forward way

    to find the lands is to seat a bullet in an unprimed case long and close the bolt. If the bullet sticks, just tap it loose with a cleaning rod. If it stuck, you can use your seater and push it back into the case by .015 and check it again after polishing the bullet with 0000 steel wool. You will probably see squarish marks left by the lands. Continue pushing the bullet into the case by say .005 each time you check to see how heavy a mark the lands are making.

    What you want to eventually see is very light marks on a polished bullet that indicate it is just kissing the lands. SAVE THIS DUMMY ROUND. You can then measure this dummy and know where the lands are. Any other equipment one might buy is a waste of money, in my opinion.

    One must do this with every different bullet they use so they know where the lands are. It is quite simple to go either into or out of the lands by using this master to measure from.
    Last edited by Pete Wass; 10-21-2009 at 07:28 PM.

  4. #4
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    I like this simple method without any special tools. But, you are using a "bullet comparator" setup to measure the cartridge base to bullet ogive distance? I guess that is where I am confused, how to measure this overall length.

    - Phil

  5. #5
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    The comparator should be measuring from the head of the case to a point
    on the curve of the bullet. The diameter at that point n the curve is fixed
    in your comparator. That dimension is only relative to your gun that
    comparator and the bullet you have chosen. Change any of those, and
    you must start over. Remove the comparator and clean the jaws of the caliper. Close them and they should read zero. If not, adjust or clean further.
    Now add your comparator pieces. By doing this, you have added a constant,
    in that your calipers are calibrated with the rest of the world. Write this
    number down, and if you loose those calipers, You can use another set.
    Add or subtract from that length as results on target require.

  6. #6
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    Mar 2007
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    I have the Sinclair device.

    and the Hornady- used to be Stony Point- device and of the two the Stony Point (Hornady) is much easier to use. Several ponts:
    1. If the bullet in the provided case does not move easily so when you push the bullet into place, often you will have the bullet "into the lands". Polish the bullet or use a magic marker on it and see it there are any marks on the bullet.
    2. Do this function a number of times and average them to get about the right length. This is why I learned another method and use it. The device hardly ever gives you the same reading twice in a row.
    3. Use a dremel tool and split the neck so the bullet moves easily in the case, once is usually enough, insert a bullet and chamber the round. Carefully extract the case and measure the OAL with the comparator. This is usually just touching or .005 in the lands.

  7. #7
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    Phil3,

    A little free advice....... CHECK YOU PRIMERS EVERY TIME you are fiddling with OAL. Whether you're making a dummy, measuring for length or playing with seating depth make SURE your primers are out of the way. Sometimes they're protruding a little, sometimes it's the cratered section around the firing pin, sometimes they just hide behind a rock and JUMP OUT!!! and bugger your measurement.......... (ac'trally they rarely do this last..... ) ...... but primers WILL sooner or later bugger a measure for you unless you learn early to check for it.

    IMO (and I am The Original Gadget Man Taylor ... I've got 'em ALL) all you need is a set of calipers and a Sinclair ogive comparator "nut"

    this thang http://www.sinclairintl.com/product/...et-Comparators

    you're good'ago

    al

  8. #8
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    Thumbs up

    IMO (and I am The Original Gadget Man Taylor ... I've got 'em ALL) all you need is a set of calipers and a Sinclair ogive comparator "nut"

    this thang http://www.sinclairintl.com/product/...et-Comparators

    you're good'ago



    Yep, it's simple and precise. Is not attached to your calipers so you can have them freed up for other tasks.

    A great gadgit.

    cale

  9. #9
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    Smile Phil ...

    Quote Originally Posted by Phil3 View Post
    I am acquiring reloading equipment (never reloaded before), and am struggling to understand bullet comparators and how they are used. - Phil
    Before you get too far out in front of things, my suggestion would be for you to find a group of benchrest shooters, attend one of their matches and start asking questions. You'll find someone, who I have no doubt, would be willing to mentor you through the whole process of reloading. You'll learn the right way and will only acquire the tools you'll need to get the job done. Let everyone know where you live and see if there is a group near you.

  10. #10
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    Phil
    You don't need a bunch of tools to find your overall length as you will rarely ever use them.
    I have the Sinclair comparator nut and its yours free of charge just for the asking.The comparator that clamps to the caliper allows you hands free operation and that is what you need.You actually need two of them one for each jaw of your caliper.
    I put the two of them on my caliper then loosen up the tensioning nuts so they align perfectly against each other then re-tighten.
    I put a bullet into them and zero out the caliper.
    Now you sit in your recliner with a bunch of bowls all around you with 0.001 or 0.002 or -0.002 written on them.You can sort your bearing surfaces on 500 bullets in no time this way but it requires one hand to install and remove the bullet and a second hand to run the caliper.
    To do that with two comparator nuts that don't attach would be maddening at best.
    Waterboy aka Lynn

  11. #11
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    Quote Originally Posted by abintx View Post
    Before you get too far out in front of things, my suggestion would be for you to find a group of benchrest shooters, attend one of their matches and start asking questions. You'll find someone, who I have no doubt, would be willing to mentor you through the whole process of reloading. You'll learn the right way and will only acquire the tools you'll need to get the job done. Let everyone know where you live and see if there is a group near you.
    Anyone in the San Francisco bay area?

    I can ask questions, and have been to matches, but I have to say, I feel pretty foolish asking these guys questions. I am brand new to ANY reloading and answers to my questions often result in the use of related terminology or processes of which I do not understand. A Benchrest reloading class would be a HUGE help!

    - Phil

  12. #12
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    Sep 2008
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    Quote Originally Posted by Lynn View Post
    Phil
    You don't need a bunch of tools to find your overall length as you will rarely ever use them.
    I have the Sinclair comparator nut and its yours free of charge just for the asking.The comparator that clamps to the caliper allows you hands free operation and that is what you need.You actually need two of them one for each jaw of your caliper.
    I put the two of them on my caliper then loosen up the tensioning nuts so they align perfectly against each other then re-tighten.
    I put a bullet into them and zero out the caliper.
    Now you sit in your recliner with a bunch of bowls all around you with 0.001 or 0.002 or -0.002 written on them.You can sort your bearing surfaces on 500 bullets in no time this way but it requires one hand to install and remove the bullet and a second hand to run the caliper.
    To do that with two comparator nuts that don't attach would be maddening at best.
    Waterboy aka Lynn
    Lynn,

    I believe you mean a set up as shown in the 3rd image found on this link.

    http://www.6mmbr.com/catalog/item/1433308/977259.htm

    To use your process, you would still need to have measured overall length with a tool and a specific bullet and then ensure the bullets all match that "master" bullet using the process you described. Does that make sense?

    I will take the Sinclair comparator nut, just for educational purposes, but I see what you mean about having to hold it, as it does not afix to the caliper.

    I can send you my address for the nut, or get it from you next time we hook up. I am going to try and attend the National Match this weekend on one day. Do all days begin early and end around noon?

    - Phil

  13. #13
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    Smile Phil ...

    Quote Originally Posted by Phil3 View Post
    Anyone in the San Francisco bay area?

    I can ask questions, and have been to matches, but I have to say, I feel pretty foolish asking these guys questions. I am brand new to ANY reloading and answers to my questions often result in the use of related terminology or processes of which I do not understand. A Benchrest reloading class would be a HUGE help!

    - Phil
    The BEST benchrest reloading class is held at every match!

    Don't feel foolish one bit about asking questions. If you don't understand the terminology ask to have it explained. That's how we all got started. There is someone out there that will take you under his wing. All you've got to do is find him and ask.

    You're never going to find a more helpful group of souls then benchrest shooters.

  14. #14
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    Sep 2008
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    Quote Originally Posted by oneflyer View Post
    and the Hornady- used to be Stony Point- device and of the two the Stony Point (Hornady) is much easier to use. Several ponts:
    1. If the bullet in the provided case does not move easily so when you push the bullet into place, often you will have the bullet "into the lands". Polish the bullet or use a magic marker on it and see it there are any marks on the bullet.
    2. Do this function a number of times and average them to get about the right length. This is why I learned another method and use it. The device hardly ever gives you the same reading twice in a row.
    3. Use a dremel tool and split the neck so the bullet moves easily in the case, once is usually enough, insert a bullet and chamber the round. Carefully extract the case and measure the OAL with the comparator. This is usually just touching or .005 in the lands.
    Given you have the Sinclair tool, what do you make of this statement from a Sinclair blog on their OAL tool. It reads in part.

    "...The Hornady/Stoney Point OAL Gauge is an easy tool to use and, we use it occasionally. It is not as accurate as the Sinclair tool because it uses factory new cases as part of the construction of the tool. The variations in headspace between the factory sized cases and your rifle’s chamber are what can cause the inaccuracy...".

    Seems to make sense, but if I resize the brass, is this really relevant? Or, upon firing, would the brass expand and move the bullet in relation to rifling before it ever left the case? Not sure it matters, since it seems to me we are after consistency, not so much exactly the distance the bullet is off the lands (hard to measure that consistently anyway).

    - Phil

  15. #15
    Join Date
    Nov 2004
    Location
    Atascadero, CA
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    329

    Smile You need some help

    I needed lots of help getting started > you will too. Best part about benchrest is the people willing to help. Come out to Sacramento on the 6th or 7th of Nov. > Folsom Shooting Facility east of town. Look me up, I'm the only Marty there! Good guys and lots of good shooting.

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