7mm rem mag new brass vs fireformed capicity help

Discussion in 'Reloading' started by rockwind, Sep 19, 2018.

  1. rockwind

    rockwind Well-Known Member

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    hi, i have found a good load of 67.3 gr h1000 for my 7 rem mag using my brand new unfired nosler brass. getting decent es and sd and good groups. however, after firing, the shoulders have reappeared about 20 thousands higher on the case, obviously creating larger case capacity. is that increased case capacity going to make any significant difference when i go to reload the fire formed cases? as far as MV? do i have to "find the node" again, so to speak, or can i just happily use my same load and expect same results with perhaps even better es/sd since the cases are fireformed?
     
  2. Gord0

    Gord0 Well-Known Member

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    You will likely have to do a little tweaking to your current load. You're going to be close, but probably running a little higher velocity with the fireformed brass. Your brass is also probably not fully fireformed yet, but the little ways it still has to go won't effect your load.
     
  3. rockwind

    rockwind Well-Known Member

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    do you think it is worth it to drop like .3 grains and see if it is brings it back to normal,,, in your experience, approx how much higher is the velocity in a situation like this?
     
  4. Mikecr

    Mikecr Well-Known Member

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    There is no credible powder development on un-fire-formed(new) brass.
    But you're closer to obtaining fire-formed brass now, and while taking care of this basic action you can do full seating testing.
     
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  5. Gord0

    Gord0 Well-Known Member

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    It's going to be 100% dependant on your rifle. Something I would do is sacrifice 1 piece of brass by firing and only neck sizing (run your full length die, but don't bump the shoulder) until it chambers a little tough. Then you can measure that and see what you headspace really is.
     
  6. rfurman24

    rfurman24 Well-Known Member

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    This is NOT true. Every single rifle I have developed a load for with new brass only needs a powder adjustment to obtain the same velocity as the load with new brass. Depending on the cartridge this is usually around .5-1.0grains lower(usually on the lower side) with magnum cartridges. An example is my first 30 nosler with new brass the load was 80.5 grains of Retumbo with a 215 Berger. Once fired brass took 79.9 to get to the accuracy node at 3030fps. The thing you do have to worry about is if you do not find the load with new brass and then try to continue development with fired brass you could be chasing your tail. I think Mikecr is suggestion doing seating depth testing while "fire forming" your brass which could help keep things consistent once you start powder charge changes. The problem with that is I have, on several occasions, found that a particular bullet may have different seating depth preferences in the same rifle depending on powder charge. What I usually do is start with a Ladder with bullets seated at the lands. I will usually find the accuracy node within 20 rounds. You can then tweak seating depth and note the velocity of the accuracy node. Once you move to fired cases check velocity and reduce powder charge accordingly. So to answer your question get the velocity of your accuracy load and adjust back to it once your new brass is all fired.
     
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  7. lancetkenyon

    lancetkenyon Well-Known Member

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    I agree with rfurman24. I have a 6.5SLR that I ran 400 pcs of brass through the FL die before fire forming, and now, 1800+ rounds down the barrel later, I am still running the exact same load that I developed with virgin brass. In the .1-.2s still.

    I have loaded for 60+ rifles starting with virgin brass, and once fired brass bumped .0015"-.002" back need very little, if any, powder changes. If anything, a few barrels that break in and gain 50-100fps are what makes a slight charge weight change needed, not virgin brass to fire formed brass (unless it is a wildcat cartridge like and Ackley, Sherman, or other "improved" case).
     
  8. rockwind

    rockwind Well-Known Member

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    thanks everyone, i appreciate the good info.
     
  9. rfurman24

    rfurman24 Well-Known Member

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    Agree 100 percent. Sometimes it is brass sometimes it is the barrel getting broke in and speeding up. In any case I have always found once I find a velocity node in a rifle with a particular bullet and powder that will always be the velocity node.
     
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  10. MagnumManiac

    MagnumManiac Well-Known Member

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    I agree with the above, however, just recently using brass I have ALWAYS used, I ran into a problem that is a first for me. I am using NEW blue bag Winchester cases in 300WM.

    I developed my loads in summer, so using the same load and once fired brass in winter SHOULD pose no problem...... not so I found out.
    The very first shot at a pig had me struggling to open the bolt, so the mob of pigs were able to escape further destruction.
    Upon opening the bolt, the case was very scuffed on the case head, the primer was VERY flat and there was a very pronounced ejector mark.

    Now, prior to heading out, I ran a dry patch through the barrel to remove any oil or ‘stuff’ left over from cleaning it, so that couldn’t have been the problem. So I decided to fire another round just to be sure it was in fact a load problem, not a gun problem. That case was also difficult to open, after opening the bolt with the rifle between my legs, the case came out less a primer....... not good me thinks.
    When I returned home, I pulled a random round and weighed the charge, it was exactly what it should have been, within +/- .1gr of 81gr.
    I am still perplexed by this, as the cases that were unfired showed no signs of excessive pressure, velocity or ANY other issue.
    I do realise that new brass takes some pressure away during expanding to the chamber, but this would indicate it is WAY over normal pressure ranges.

    Anyway, thought this may be interesting.

    Cheers.
    :confused:
     
  11. rfurman24

    rfurman24 Well-Known Member

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    If you are at or near max with new brass you are flirting with danger using the same charge with once fired.
     
  12. corsair4360

    corsair4360 Well-Known Member

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    The biggest question is how large is the chamber? I had a 7mm Rem Magnum years ago that had a monstrous chamber (factory rifle), so large that three times fire formed and neck sized brass had the belt about 0.030" off a straight edge held on the case wall. In that case, the fireformed brass was necessary to come up with a good load... That rifle would shoot a 1/2" three shot group out of a cold clean barrel every time with my H870 handloads and fireformed brass.
     
  13. MagnumManiac

    MagnumManiac Well-Known Member

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    It definitely appears to be at max, but with the pressure trace on a previous bag of the same lot number, I am only running around 61,000psi. This was tested on once fired brass.
    I have not tested this bag of brass, as my laptop screen broke.
    Case capacity, measured in CC’s, shows it is the same between bags, I guess the hardness may be different.

    I do not know the cause, but it has definitely got my attention.

    Thanks for the reply Rfurman.

    Cheers.
    :)
     
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