any special tricks to handloading Belted Mags?

Discussion in 'The Basics, Starting Out' started by NotEnoughTriggerTime, Aug 25, 2004.

  1. NotEnoughTriggerTime

    NotEnoughTriggerTime Active Member

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    Just came across a 7mm Rem Mag, and plan to handload for it.

    this is my first experience handloading for a Belted Magnum, wondering if there is anything special that I should know when buying dies and equipment.

    Its a bolt action - is neck sizing only a good option?

    any suggestions are appreciated.

    Thanks in advance.
     
  2. Aussie

    Aussie Well-Known Member

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    NETT ,
    Neck sizing is a good idea as long as you use a proper neck sizing die and your loads aren't so hot that FL sizing is required every shot. Check that fired shells rechamber easily before choosing whether to NS or FLS .
    Minimum FL sizing is also o.k. . Start by setting up your FL die so it doesn't quite touch the shellholder and adjust your die down in the press a little at a time until resized cases will rechamber with just a little resistance when lowering the bolt handle .
    Many people overdo it when FL sizing belted rounds . This shortens the case from rim to shoulder and causes excess headspace which ultimately results in case head separations . Belted rounds have a bad name because many people size them incorrectly .
     

  3. Mysticplayer

    Mysticplayer Writers Guild

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    Assuming your loads allow the fired brass to easily rechamber, neck sizing is the way to go. My suggestion is to get set of Lee Delux dies in that cartridge. It will come with a FL size and collet neck sizer.

    I use the collet neck sizer for almost everything I shoot and it produces very concentric necks. The FL die will be there if you need to bump the shoulder back as Aussie described.

    When the base gets too big to chamber easily, I pitch the brass as head separation WILL happen if excessive sizing is done.

    Jerry
     
  4. johnny k.

    johnny k. Well-Known Member

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    NETT,
    Nothing special that I know of. I have a 7mmRM also and use plain ole RCBS FL dies. When working up loads for target shooting I would re-adjust the die to only neck size previously fired brass, but if loads are to be used for deer season then brass was FL resized.
    Good luck. Johnny K.
     
  5. Aussie

    Aussie Well-Known Member

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    NETT and JohnnyK ,
    Neck sizing with an FLS die can result in headspace problems as normally you will find that body of case will be partially sized even when you back the die off . Can't usually do neck only . That's why we have neck sizing dies .
    Have no experience with the 7mm RM specifically but generally not recommended practice .
     
  6. LB

    LB Well-Known Member

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    Aussie, would you please explain your response a little more fully?

    I use full length dies on Magnum cases, as well as neck size dies. I have also partially full length sized brass without a belt, a number of times.

    What I don't understand is how this process can create "headspace" problems, when using brass previously fired in the same rifle?

    Thanks. LB
     
  7. Aussie

    Aussie Well-Known Member

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    LB ,
    I've not had this problem personally but have read that normally the case walls are slightly reduced in diameter or compressed by the FLS die prior to the die headspace shoulder making contact with the case . As a result of this compression the case is inclined to lengthen from base to shoulder . If the die is not adjusted properly (as happens when using FLS dies to neck size) then the case shoulder is not forced back to it's proper position .
    The end result is a case that has longer headspace than it did originally . This of course can make cases hard to chamber until full length sized properly .
    If your rifle has a "long" chamber and/or you are using "short" brass (as is often the case when people overdo their full length sizing) you may not ever notice a problem .
     
  8. Ian M

    Ian M Well-Known Member

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  9. COBrad

    COBrad Well-Known Member

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    I'm a big fan of the 7mm Rem mag. If I were limited to only ONE centerfire rifle for everything from prairie dogs to elk, it would be chambered for the 7 mag. That said I don't currently own one! I have, however loaded for 3 different belted magnum rifles over the past 10 years or so, with great success. What has worked for me is to routinely neck size using a neck die, not a FL, and I use the FL die to set the shoulder back no more than necessary to just "feel" the case when the bolt closes, usually .001-.002, when the case gets difficult to chamber. I use a Stoney Point comparator to accurately guage my resizing. I also use a set of Redding Competetion shell holders to adjust resizing rather than backing my dies off. The use of the shell holders allows me to square the die body with the shellholder, as per the die instructions, during initial set-up, and then maintain that condition while adjusting case length for optimum head-space. As mentioned by Aussie, partial sizing in a FL die has, for me, created a condition of excessive shoulder length. I usually get a half dozen or so reloads out of a case before tossing it by using this procedure. I also generally use the most accurate load I can find, which is usually not the max load. The exception to this is a .300 Jarrett I use for elk. It shoots well using max loads. I still get that half dozen reloads, but shoulder length is critical. If I FL resize more often than necessary, or more than the .001 or so for smooth bolt operation, I start getting thin case walls just above the belt. That's my $.02. [​IMG]
     
  10. nottoofar

    nottoofar Active Member

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    I have reloaded for the .300 win mag belted case for years.
    I set the sizing die to where it is almost touching the cartridge holder on the down stroke, all I want to do is adjust the neck.
    After 2-4 uses the case will start getting too tight to chamber easily then I full length resize for a couple more uses then toss the brass. Never had a case separation.
     
  11. larrywillis

    larrywillis Well-Known Member

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    Fellow Shooters,

    Take a look at the homepage on our website www.larrywillis.com It's the most complete information available on reloading belted magnum calibers. There is also a Question and Answer section and a Testimonials section (along with lots of reloading tech tips.)

    Good shooting,
    Innovative