nosler 7mm rem mag shoulder grows .022 after first firing, normal?

Discussion in 'Reloading' started by rockwind, Aug 29, 2018.

  1. rockwind

    rockwind Well-Known Member

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    so as mentioned in previous post, i have a saami spec 7mm rem mag. new nosler brass. loaded up for a ladder test. the mild loads grew by .022 and the higher end loads grew a a little more. i've only loaded for 3 other guns, a 308 and 2 different 6.5 saums so i am wondering if this is normal? my 6.5 saums don't grow at all it seems. anyway, i will do the usual headspace check and probably wind up bumping the shoulders the usual .002-.003. but is there something special about these 7 rem mags? thanks
     
  2. MagnumManiac

    MagnumManiac Well-Known Member

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    Yes it is normal.
    Belted mags headspace off the belt, so the head to shoulder length on factory ammo/cases aren’t held to any close spec.
    My 338’s grow on average .016”, as do my 264’s, but my 300WM’s grow between .020”-.026” on SAAMI chambers. On my A191 300WM chambers, the shoulder is held to .008” over unfired brass, this helps quadruple brass life.

    Cheers.
     
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  3. J E Custom

    J E Custom Well-Known Member

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    Ditto.
    Belted cases are sized much smaller than shoulder cases the first time so they can be fired in a dirty chamber. If you full length size them, they will increase in length a great deal each time.

    If you do a minimum sizing after fire forming (Just enough to chamber) you will be using the case like a shouldered case and growth will be held to a minimum.

    Don't bump the shoulder at all until it becomes hard to chamber then only bump just enough to chamber and no more. I use neck dies for this and a bump die when it becomes tight or hard to chamber

    Once a belted case is fired, it becomes a shouldered case and can be loaded like one unless you full length size it. I recommend sizing to fit the chamber, not the belt after it has been fire formed unless you are hunting dangerous game where brass has to take a back seat to safety and chambering can mean life or death.

    J E CUSTOM
     
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  4. rockwind

    rockwind Well-Known Member

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    the most dangerous wild game around here is my wife so i will follow your advice. thanks! that was my plan anyway, i just am not used to the shoulders growing so much.
    since i was load developing with this new nosler brass and i came up with a good "node",,,, once i start using the fireformed brass, it seems like the case capacity will increase a lot, is it going to affect my load much, in my mind, if i found a good node at say 2975 fps with my 180 hybrids, all i have to do is adjust my powder charge in the fireformed cases to get me the same MV? is it that easy?
     
  5. J E Custom

    J E Custom Well-Known Member

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    The powder capacity will increase because the shoulder is being blown forward, but it may not hurt the accuracy. In fact the accuracy should get better after fire forming. I find good accuracy while fire forming AI cases, but accuracy improves with good chamber fitting cases if sized only enough to chamber.

    You may have to adjust the powder charge a little but to start with try your pet load first, then adjust if you need to.

    J E CUSTOM
     
  6. rockwind

    rockwind Well-Known Member

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    i don't have neck sizing only dies, just a whidden full length bushing die. so my plan is to just bump the shoulders as little as possible (checking them in the chamber of course), i have had not good results in the past using full length bushing dies to just neck size without touching the shoulders, maybe i was doing something wrong. are belted magnums a different animal when it comes to neck sizing, is that the way to go until they don't fit anymore?
     
  7. J E Custom

    J E Custom Well-Known Member

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    Belted cases were designed to work in any chamber and the belt keeps the head space under control even though the case body is much smaller than the chamber. Firing a belted case the first time is like fire forming a wildcat to a different chamber. after the first firing minimum sizing is the way to go.

    Full length dies are made to size the belted case back to a much smaller dimension (Like the original size). If you use full length dies and "Bump" the shoulder you will full length size plus the Bump.

    The two options are to full length size and live with the case growth and a short case life or neck size only and have a good chamber fit and case life.

    J E CUSTOM
     
  8. Black Bart

    Black Bart Member

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    I also just started working up a load for a 7mag. I made a fire form load with 162 amax jammed into the lands and a light charge (starting load in the book). used my magneto speed and got 2600fps. This blew the shoulder forward .016-.019. I then used a redding body die set just short of touching shoulders. This lengthened the shoulders to .022-023. At that point I tried to chamber the brass and felt a fair amount of resistance on closing the bolt. A lot of my brass ended up at .020 after 2nd firing and with a little springback I think this is about .001 short of my actual chambers shoulder. I have had good luck using a redding body die and a lee neck collet die for several guns.
     
  9. Black Bart

    Black Bart Member

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    I should also add that I will bump my shoulders back to .019 with the body die. This should put my shoulders at -.002 of headspace.
     
  10. rockwind

    rockwind Well-Known Member

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    hi JEC, you obviously know your stuff. when i bought the full length sizer set from whidden, they told me that the belt handles the headspace, (once the shoulder is bumped back from the chamber shoulder.) so maybe i am not understanding, i am probably missing something. i understand neck sizing, i just don't have one but i can get one of course. black bart below mentions he bumps shoulder a small amount with a body die, i realize i have a full length die but i thought it just leaves the neck alone is all. guess the part i don't get is why can't i adjust the full length sizing die to just bump the shoulders .002, so they fit up against the shoulder part of the chamber nice and close but not touching?. i realize now that doing so isn't for headspacing. i don't get why you say i have to go all the way back to, for example, the factory shoulder length .020 shorter shoulder vs just .002 or.003.
     
    Last edited: Aug 30, 2018
  11. cape cove

    cape cove Well-Known Member

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    I have 5 belted mag chamberings and use my full length sizer die to bump the shoulder .002 after the first firing and have no problems. Some times with certain chambers when you have your die adjusted this way you could get a bulge forming just in front of the belt. When this happens you have basically 2 choices, one would be to lower your sizer die to size this portion of the case but this pushes the shoulder to much and the result is very poor case life, even seperations. The other would be to purchase a Larry Willis die which is designed to solve just this problem.
    http://www.larrywillis.com/
     
  12. MagnumManiac

    MagnumManiac Well-Known Member

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    Using your FL bushing die to reduce the shoulder .002” will also reduce the body diameter by roughly the same amount. This is known as Partial FL sizing.
    This is what I do and recommend.

    As to the bulge, if it occurs, it is due to chamber problems, not brass problems unless it is Norma brass that is thin in the web.

    Cheers.
     
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  13. rockwind

    rockwind Well-Known Member

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    i sized 30 already for first time with the whidden FL bushing die. turned out good, the bottom part of the die is so close to the belt, i don't see how there could be a bulge, unless it is tapered somehow. but there is a little cut out in the bottom of the inside of the die for the belt to go into.
     
  14. DUSTY NOGGIN

    DUSTY NOGGIN Well-Known Member

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    check if they fit chamber. if so, load em up

    your die measurement 1/16 " away from that belt . may be looser or tighter than your rifles chamber.

    if you dont bring the die down all the way (- .018) , it doesn't squeeze that area over the belt as much either ( as magnum said above ) .. but if it fits in your chamber after partial sizing, the your rifles chamber is large enough to not matter

    if it doesn't fit , that is where the belt collet will help because you can still do your (-.002) size to shoulder. then, on separate operation bring that belt line in to fit with the belt collet die
     
    Last edited: Aug 31, 2018