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Thread: Resizing 7mm Mag brass to 264 Win Mag

  1. #1
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    Resizing 7mm Mag brass to 264 Win Mag

    I was under the impression that all I had to do to make 7mm Mag to 264 win mag was to resize it through the 264 sizing die and trim. So I made about 50 of them. Yesterday I got my 264 together and went to test fire it. I used 55.5 grains of 4350 to start, bout midway still 4 grains from max, I got a sticky bolt after the shot. No flattened primers or dimpled primers so I am thinking that I got the headspace right. I came back home and loaded up 3 more at 55 grains and still the sticky bolt. So I bought a box of Winchester 140 grain factory. They shot just fine. No sticky bolt!

    So my question is what did I do wrong with my 7mm brass? The only thing that I see that is different between the two is the distance between the base of the case to the base of the neck. Is that causing me my problems. Or do I need to ream out the necks.

    Ryan
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  2. #2
    nastynatesfish
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    I'm getting the same thing with brass that I made from norma 243 to run in my 260. I see a little donut at the base of the neck, I think that's what the problem is. Maybe need to turn your necks. I tried screwing the sizer down farther also to no avail

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    Well I am glad to hear that I am not the only one with this problem! I am sorry that you are having issues too! I also see that little doughnut on the neck. So I guess the answer here for me is to order 264 brass! I cannot measure from the base of the case to the base of the neck accurately enough with my calipers to see if there is any real difference. I also cannot see a difference between the neck size on loaded 264 brass and the 7mm. Same with fired..... But something is different thats for **** sure.

    Wilcox? I have a buddy that works for the City there. Or use to anyway. He might be retired. I just retired out of Cottonwood. Sure dont miss that heat!

    RYan
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  4. #4
    nastynatesfish
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    I ordered 200 pcs Norma 260 so I think I'm gonna wait for it to get here to try more also. I cannt get it to shoot at all. I used to work for the city also. Back in 2005. Ya but it's a dry heat lol

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    Do you know Tim Bear? Like I said Im not sure that he is still there. I went to the academy with him.....

    I had problems with my son's 260 when I necked down 308's. Some real problems.... blown primers and such.... Since I went with the right brass not a single issue with it.... So what I am hearing is that we need to be shooting the right brass.... lol
    MOAON AABE

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    Ok I just had a thought....

    I have been going over my reloading manuals for two days now looking at the differences between the 7mm mag and the 264 win mag case. The only difference that I can find is that on the 264 the distance between the base of the case to the base of the neck is: 2.2459 and the 7mm mag is 2.2287. That is a difference of .0172 (headspace error right)? So my thought is that if I am bumping the neck too far back then that is going to cause the cases to streach and my pressure problems. In theory.

    Am I on the right track here? Now I also know that I cant measure that exactly with a set of calipers. There is just too much room for error.

    Any thoughts?
    MOAON AABE

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    Spend the money on a Hornady cartridge headspace gauge and you will be able to measure your brass from base to a datum line much more accurately.
    http://www.hornady.com/store/Lock-N-...h-Body-1-Each/
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    I ran into a similar problem necking down .300 WM cases for my 7MM Mashburn Super. My issue was neck thickness, there was not enough room for the bullet to release cleanly, solution was to turn case necks a little.

    Bob
    It's better to shoot for the moon and hit the fencepost than to shoot for the fencepost and hit the ground!

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    Quote Originally Posted by RyanG View Post

    That is a difference of .0172 (headspace error right)?
    No, the difference is a result of how far the neck protrudes into the shoulder, the larger the neck diameter the shorter the length from the case head to the neck-shoulder junction. It has nothing to due with headspacing or head clearance however.

    Your 264 FL die wouldn't fully resize the neck, it longer than the 7 brass at the junction. Its why when I make 30-338WMs with 338WM brass I NS only with a bushing die. After fire forming I ignore the belt and use a shoulder bump. If I use 7 brass I use my 30 die.

    As far as the neck diameter, you'll have to do some measuring. You can make a chamber cast or use a small hole gauge and mic to get the chamber neck diameter or get a ballpark figure by measuring a few fired cases.

    How did you setup the barrel, on the belt or the shoulder?

    Bill
    I'm the luckiest fisherman in the world, I married a girl with worms.

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    I used the belt. Im not sure how to use the shoulder. I purchased a set of Pacific go/no go gauges. I like I said.... or ment to.... it shoots factory ammo just fine.... So I am not exactly what I did wrong with the brass. I see what you are saying about the necks being too long. I there something else I should do here about the headspace?
    MOAON AABE

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    Quote Originally Posted by RyanG View Post
    I used the belt. Im not sure how to use the shoulder. I purchased a set of Pacific go/no go gauges. I like I said.... or ment to.... it shoots factory ammo just fine.... So I am not exactly what I did wrong with the brass. I see what you are saying about the necks being too long. I there something else I should do here about the headspace?

    No, it sounds as though you put it together OK.

    Generally most, myself included using virgin belted brass use the belt, but after forming size the brass casehead to shoulder the same as a rimless bottle neck cartridge.

    I don't think you did anything wrong as such, but your 264 die probably can't fully resize the neck because its .172" longer casehead to the junction than the 7RM brass. Why you get the bulge in the necks.

    Unfortunately there is only two easy fixes. One use 264 brass or two, use a bushing die to size the necks only. As I said, when I make 30-338s using 338WM brass and neck them down with a 30 bushing.

    Just for S&G, resize a few sticks of the 264 brass paying close attention the the shoulder bump. My guess is it will work.

    Bill
    I'm the luckiest fisherman in the world, I married a girl with worms.

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    Quote Originally Posted by BillPa View Post
    use a bushing die to size the necks only.
    Bill
    I tried this last night with virgin 7mm R-P cases using my Redding .264 bushing die, it worked fine. Just as an aside, my .264 shows pressure signs with factory 140 grain Remington ammo, ejector marks on the case head and loose primer pockets. I suspect that my old factory ammo is a little on the soft side brass wise but I haven't shot the gun enough to know for sure. I'm going to run a batch of handloads through it this weekend then I should know more.

    Bob
    It's better to shoot for the moon and hit the fencepost than to shoot for the fencepost and hit the ground!

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    Bob,

    I am wondering how it worked for ya this weekend. I broke down and bought Norma brass and waiting for a day to get out and shoot it with that.

    Ryan
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    Hey Ryan,
    The brass worked great, the problem with the Remington factory ammo was not related to age. The rifle has a short throat and the bullets were touching the lands, the factory ammo was simply too hot for this particular rifle. My Redding sizer only sizes about half way down the neck of the R-P 7MM Mag case, I thought this might cause a little problem but that was not the case, no trouble with the brass at all. I worked up to a book max load of R-22 and 140 grain Ballistic Tip seated .005 off the lands sparked by a Federal 215.

    I bought some Norma brass last year for my .25/06, it's really good stuff! Let me know how you like the .264 stuff, I may have to try some of that too.

    Bob
    It's better to shoot for the moon and hit the fencepost than to shoot for the fencepost and hit the ground!

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    Different cartridge but same idea. Anybody tried forming 7mm Remington brass to .257 Weatherby?
    There are 3 kinds of people in this world. Those who can do math and those who can't

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