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Thread: HELP which headspace comparator

  1. #1

    HELP which headspace comparator

    Help please, I want to bump the shoulders back on all my 6.5x47 cases but reading the back of the hornady headspace comparator kit 6.5x47 must be one of the only cases that's not mentioned. If anyone knows which of the collets it is I'd be very much obliged
    Regards
    Jimmy
    Next time you're walking down the street and see a homeless person go buy them a sandwich and a coffee, change of fate and it could be you one day !!!

    BUY BRITISH !!!!

  2. #2
    if you run into problems with your current kit, then you could do worse then ring David at the Shooting Shed
    "Politicians must be allowed to panic. They need activity. It is their substitute for achievement"
    "'The matter is under consideration' means we have lost the file. 'The matter is under active consideration' means we are trying to find the file."

  3. #3
    Jimmy
    You need bushing "C" (0.375") that is the nearest for your cartridge- It will allow you to do comparative measurements - It's not absolute measurement that is necessary, i.e. you need to compare the reading on cases before & after bumping back, or of a case against a headspace GO gauge that is made for your specific cartridge. - It is not the exact length that matters - it is the difference between the two measurements that gives the amount that you have bumped back.

    You can use the comparator to allow you to measure a case that just alows you to close the bolt with the minimum resistance - this value will be the absolute maximum length that your resized cases should end up after bumping - ideally you need to bump back a couple of additional thousands of an inch.

    Ian

    p.s. You might find the following of interest, there is a link on there to download a copy of the cartridge drawing.---- 6.5x47 Lapua Benchrest--New Cartridge Info

  4. #4
    Quote Originally Posted by Yorric View Post
    Jimmy
    You need bushing "C" (0.375") that is the nearest for your cartridge- It will allow you to do comparative measurements - It's not absolute measurement that is necessary, i.e. you need to compare the reading on cases before & after bumping back, or of a case against a headspace GO gauge that is made for your specific cartridge. - It is not the exact length that matters - it is the difference between the two measurements that gives the amount that you have bumped back.

    You can use the comparator to allow you to measure a case that just alows you to close the bolt with the minimum resistance - this value will be the absolute maximum length that your resized cases should end up after bumping - ideally you need to bump back a couple of additional thousands of an inch.

    Ian

    p.s. You might find the following of interest, there is a link on there to download a copy of the cartridge drawing.---- 6.5x47 Lapua Benchrest--New Cartridge Info
    Much obliged Ian a good read that.
    Regards
    Jimmy
    Next time you're walking down the street and see a homeless person go buy them a sandwich and a coffee, change of fate and it could be you one day !!!

    BUY BRITISH !!!!

  5. #5
    To determine the correct head space in a rifle is a very useful piece of data and I do it this way:


    Take a cartridge case that has been fired in the rifle you’re measuring and with the case unsized but the primer de-capped (Using a de-capping die). Using a head space measuring tool such as Hornady’s, http://www.hornady.com/store/Headspace-Gauges/ fitted onto your zero’d vernier and measure the fired case dimension:


    Take the fired case and place it into your rifle breech/chamber. Then, using some paper or aluminium baking foil cut into small pieces, place the paper/foil as packing at the cartridge head (base) and continue doing so, one piece at a time until the bolt will close down – but – tightly – in an undesirable condition.
    Do this as carefully & accurately as you can.
    This will give you a ‘No-Go’ dimension. In other words, you now know when a cartridge is resized to this dimension, it will not chamber correctly in your rifle.


    Then repeating the process until the point where the bolt locks down smoothly with normal light resistance, Remove the paper/foil cartridge with the packing in place, using the head space tool on your vernier, take the measurement. and you should now have a new measurement, the correct head space dimension you should resize fired cartridge cases to. The 'Go' dimension.
    This dimension should be the correct headspace measurement and is usually different to the fired case dimension. (slight difference). There will be some differences if a number of cases are measured and a mean average should be taken of fired case dimensions for setting up the resizing dies.


    Note down the Go/No-Go with the correct head space dimension you want to resize your brass to for future reference.


    The above takes a little ‘messing about’ but the advantage of getting these dimensions correct and being able to utilise them to set your full length resizing die accurately is greatly beneficial.
    Last edited by deeangeo; 28-04-2015 at 21:37.
    Blaser K95 Luxus Kipplaufbüchse .25-06Rem. Zeiss 8x56, 110gn Nosler Accubond = Game Over!

  6. #6
    Thanks that's one for the weekend when she out and the tables free.
    Regards
    Jimmy
    Next time you're walking down the street and see a homeless person go buy them a sandwich and a coffee, change of fate and it could be you one day !!!

    BUY BRITISH !!!!

  7. #7
    the switch between measuring a case adapted to a NO-GO gauge and measuring the resized case is where things can go wrong

    chamber a sized case constantly increasing the depth of the die by 1/8th of a turn to get both the point between crush fit and not crush fit and also the absolute point of the die

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