Neck turning



  • I'm trying to unfuck the huge variation in neck thickness on this Peterson match brass. I'm having a little difficulty getting my cut right and I'd like some input.

    My procedure is this.
    First I take a virgin piece of brass and full length size it in a whidden die without the expander to tighten up the neck. Then it gets expanded with the 21st century expander die. Then trimmed to length and put in the lathe.

    The problem I'm having is an inconsistent cut up the shoulder. On about half the case the cut ends ~.030 into the shoulder on the other half it takes way more than it should. I'm not getting a lip or sharp edge, the cut transitions smoothly into the shoulder. '2309kUv.jpg
    Is this an issue of new/crappy brass with the shoulder being inconsistent or am I doing something wrong?



  • @ragnarnar said:

    Is this an issue of new/crappy brass with the shoulder being inconsistent or am I doing something wrong?

    Crappy brass from the bottom to the top would be my guess. If you've got a nice fit on the turning mandrel, your case can't be wobbling far enough to do that.



  • I was figuring it had something to do with that.

    I took a mic to the mandrels they come in at .3077 and .3062, expanding and turning respectively.
    That's a difference of .0015 between each, tight IMO.

    Would firing the brass to blow the shoulder forward do anything to even it out? If so I may load up 50 or so pieces with throw away bullets and use them to break in the the 308 you're building for me to see if that does anything to help the brass.



  • @ragnarnar
    You're actually going to have a closer fit even than that .0015" due to spring back on the brass.

    I wouldn't hesitate to try popping a few out to see if that straightens it out a bit.

    I've turned fired brass before and you still see that unevenness a bit but definitely not as bad as you're seeing.



  • I got in contact with John at 21st Century shooting, the maker of my neck lathe.

    This is his reply

    This is very common. There is nothing you can do about it. When the neck & the body of the case is not concentric, this is what you get. Don't worry about it.

    I always try to fire form the case first, IF there is enough clearance in the neck area of the chamber. in other words, Load & Shoot & then turn necks. You'll find that if the chamber is concentric, you will have much better luck, It will come out better.

    I suppose I could have checked that if I had a concencentricity tool. Next tool purchase is upgrading my press and then that.

    So for now I'm going to load up a bunch of throw away bullets and cheap powder, and see if I can't improve this brass some before I turn it.



  • The peterson brass is not looking too hot in my opinion. I am sure you can make it work...but it is taking a lot of effort to get it there.

    BTW-- don't buy a Hornady concentricty gauge. Mine has about 0.003" of slop...so you really can't tell if it is concentric or not.



  • @dddoo7 said:

    The peterson brass is not looking too hot in my opinion. I am sure you can make it work...but it is taking a lot of effort to get it there.

    BTW-- don't buy a Hornady concentricty gauge. Mine has about 0.003" of slop...so you really can't tell if it is concentric or not.

    It's a little aggravating, you are correct.... but I've always been told brass isn't up to its potential till its been fired at least once. For all I know I could be doing this when I squeeze the neck down then expand it up.

    I do take some heart, I've found more than one serious review since I bought it where its been compared to lapua in terms of hardness and case life.

    Thanks for the heads up, I'm eyeballing this one because the service I've gotten from 21st Century
    http://www.xxicsi.com/concentricity-gauge.html
    Or this one from accuracy one
    http://www.bullettipping.com/products_concentricitygauge.html



  • I'm close to giving up on the Peterson brass as well. I'm getting ready to resize after my second firing. If the neck concentricity is still all over the place with many greater than 0.003 in runout then I'm done. On a side note I have a Sinclair concentricity guage and it works very well. I can see the "wheels" in the two setups above being very handy and speeding up the process.


 

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