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Thread: Minimum Neck thickness

  1. #1

    Minimum Neck thickness

    Just looking to tidy up some .20 TAC Dakota brass and turn the necks to get them even. i have found some cases are nearly perfect in the necks and others are varying thickness by about 0.002". Now the narrowest measurement i have found is 0.012" thick so im planning to just trim down to 12 thou for all cases (minimum thickness is 12 thou max 14).

    Now i guess these are not massive thickness variations but as i have a good barrel, done by an excellent smith, i think its only sensible for me to try all i can to get things spot on. Plus im on call so i cant have much other fun!


    Basically, is a neck thickness of 12 thou going to be ok? i cant see why not but i just thought i would ask some more experienced people.

    Many thanks and Happy New Year to Everyone!

    Regards

  2. #2
    Quote Originally Posted by hcm1 View Post
    Just looking to tidy up some .20 TAC Dakota brass and turn the necks to get them even. i have found some cases are nearly perfect in the necks and others are varying thickness by about 0.002". Now the narrowest measurement i have found is 0.012" thick so im planning to just trim down to 12 thou for all cases (minimum thickness is 12 thou max 14).

    Now i guess these are not massive thickness variations but as i have a good barrel, done by an excellent smith, i think its only sensible for me to try all i can to get things spot on. Plus im on call so i cant have much other fun!


    Basically, is a neck thickness of 12 thou going to be ok? i cant see why not but i just thought i would ask some more experienced people.

    Many thanks and Happy New Year to Everyone!

    Regards
    You should ask your gunsmith. He cut the chamber and should know the dimensions.~Muir

  3. #3
    Distinguished Member Ronin's Avatar
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    .012" should be fine, it used by me in several of my rifles with fitted necks.

    I wouldn't go much less than this though,

  4. #4
    I shall ask next week to be sure.

    In the meantime, i have measured 8 fired cases and they all measure 0.233 inches across the neck.

    So taking 0.204 as the bullet diameter, plus 0.024" (both sides of a 0.012" neck) gives 0.228" total diameter of a loaded case neck.

    this would translate into a 2.5 thou clearance between the neck of the cartridge and the side of the chamber.

    That seems ok from bit si have read but should i be hoping for less?

    thanks for the replies Gents.

  5. #5
    How true (or safe) this is I don't know, but when I started to form and prepare brass for 6mmPPC I was told to try
    and end up with the neck of a loaded round sized .0005" to .001" smaller than the chamber neck.
    If I got it right I was told I should be able to reload a few times without re-sizing, if it needed to be re-sized every
    time I had gone to small. All went well, very accurate and yes I could just re-prime, add powder and bullet and go again.
    (but didn't, other than to prove it would work)

    Neil.

  6. #6
    Quote Originally Posted by hcm1 View Post
    I shall ask next week to be sure.

    In the meantime, i have measured 8 fired cases and they all measure 0.233 inches across the neck.

    So taking 0.204 as the bullet diameter, plus 0.024" (both sides of a 0.012" neck) gives 0.228" total diameter of a loaded case neck.

    this would translate into a 2.5 thou clearance between the neck of the cartridge and the side of the chamber.

    That seems ok from bit si have read but should i be hoping for less?

    thanks for the replies Gents.
    Closer than .0025" clearance? Why? Do you think the neck will hold the bullet as it leaves the case? Guiding it while it transitions into the rifling?? It doesn't. I'm guessing 20 TAC is for field use, not BR. If so, you should have ammo that is suitable for field use. It doesnt' take much crap to to clog off .0025 inches and it would get ugly if it did. JMHO.~Muir

  7. #7
    thanks for the responses. It is a steep learning curve but i learning all the time.

    cheers!

  8. #8
    hcm1, are you using bushing dies? if not then its not worth the effort of neck turning unless your necks are to big for you chamber but if you are then its a necessity.

    Ian.

  9. #9
    there's no minimum. find out your neck diameter for your chamber, i doubt it will be a tight neck chamber as it should be engraved on the side if it is/and or your gunsmith would have told you and discussed it with you???. so you don't want to clean them up too much, shoot for a 70% clean up and leave it at that. if you're not using bushing dies, this may affect neck tension. get a book on benchrest shooting/reloading and learn a bit about your hobby, and don't believe everything you read on shooting forums....

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