1st loading of brass is great, 2nd loading stinks. Can you help?

Discussion in 'Reloading' started by timotheius, Oct 30, 2018.

  1. timotheius

    timotheius Active Member

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    I could use some help with my load work up for my Sako A-7 Roughtech chambered in .270 winchester. When I handload brand new Hornady brass, it shoots 3/4 inch groups and I am very satisfied. However, when I reload that exact same brass after it has been once-fired, groups open up to about 1.5 inches. What's going on?

    I am using a bunch of brand new, unfired bulk Hornady brass, 130 grain Sierra Game King bullets, and 61.6 grains of H4831 powder. I am also using a Redding full length bushing die with a .302 bushing. I take the new brass and run the expander ball down the mouth in order to uniform it. Then, I remove the expander ball and full length size the new brass with a .302 neck bushing. (this does very little sizing on any of the brass, but I still feel like helps to keep things uniform.) I then load it and seat the bullet with a Lee seating die. Take it to the range, and get great results. Then I take the brass home, tumble it, lube it, and FL resize it with the same neck bushing, but using no expander ball at all. (I rely on the boat tail bullet to do the expanding when the bullet is seated). I load it with the same load, take it to the range, and it shoots like crap. Do you have any idea what is causing the inconsistency between the first and second loadings/firings of this brass?
     
  2. Hand Skills

    Hand Skills Well-Known Member

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    Have you measured case capacity of new vs once fired brass? Could be some changes going on there, and you might need to adjust charge weight accordingly
     
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  3. Barrelnut

    Barrelnut Well-Known Member

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    Also, guessing that maybe overall length maybe different due to different seating pressure, and different seating pressure may be causing runout. Do you have a gauge to measure runout?
     
  4. Dr. Vette

    Dr. Vette Well-Known Member

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    I had the same thought.
    Since the case capacity went up, you may have to bump your load a bit to get back to the same spot. Use a chronograph to look for the same speed.
     
  5. timotheius

    timotheius Active Member

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    Thanks for the replies. No, I haven't measured case capacity. All I can say is that the powder looks to be in the same place in the case each time. 61.6 grains pretty much fills up the case all the way to the bottom of the neck.

    I do have a Forster runout gauge, I'll check out the runout issue. Also, I'll try increasing the load a bit and see if that makes a difference.
     
  6. rfurman24

    rfurman24 Well-Known Member

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    Typically what causes your issue is new brass uses some of the energy to expand the case to the walls. Once fired doesn't do this so pressure goes up therefore velocity goes up. If your accuracy node is smaller than the change caused by this, groups will open up. If I were you and you have a trustworthy chrono(not a cheap optical) I would measure your new brass load velocity and once fired. I suspect you will find the once fired 20-40fps faster. If this is the case back the charge off to the speed of your accuracy load. If you do not have a good chrono I would back the charge off 1 grain and work back up.
     
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  7. timotheius

    timotheius Active Member

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    That's sounds good. I have a Magneto speed V3. I believe that should give me pretty reliable chrono results. I'll give that a try.
     
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  8. Axl

    Axl Well-Known Member

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    +1 for what rfurman said
    also I would
    bump the shoulder back a .001 or two
     
  9. sedancowboy

    sedancowboy Well-Known Member

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    rfurman has given you good advice. I have loaded for the 270 win for 49 years. 61.6 is a hefty charge most times 60 grs of H 4831 is plenty with a 130 gr bullet. Try backing off a bit. I can bet that Hornady brass will not last long at those charges.
     
  10. timotheius

    timotheius Active Member

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    Thanks for your input. The reason I went as high as 61.6 grains of H4831 is because I was trying to get to 3100 fps. 61.6 got me to 3060 fps according to my magnetospeed. (24.4 inch barrel, 1-10" twist) That charge grouped well at first, and pretty much filled up the whole case with powder. Anything more would have been a compressed load with the H4831. However, I will back the charge down some and see where that gets me. I guess if I had to choose, I would much prefer MOA accuacy over an extra 50 fps in velocity. And you are right about the brass, after 4 firings several pieces of the brass developed a uniform crack around the case body about 1/4 inch above the case head.
     
  11. jasent

    jasent Well-Known Member

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    thats case head separation. Caused from over sizing your brass. Bumping shoulders too far back
     
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  12. DUSTY NOGGIN

    DUSTY NOGGIN Well-Known Member

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    hodgdon data has 60 grains as compressed , with case separation .. thatll blow your eyeballs wide open

    that should all be reviewed and verified , before you keep going
    as far as your reloading , i think if you should add a step to run over an expander mandrel prior to seating , so the seating opens up them up the same

    seating jump to lands measurement needs to be always be greater than case shoulder to chamber shoulder gap headspace distance ... at least until you understand the spike in pressure that can happen if your firing pin jams your bullet into the lands because the brass shoulder didnt stop it
     
    Last edited: Nov 1, 2018
  13. DocDoc

    DocDoc Well-Known Member

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    You should buy a comparator with right collar to fit the case shoulder angle for the .270 case. Use it to measure the distance from base to shoulder of the fired case. Bach off your sizing die so you are shortening that by no more than 0.002 in. That will end the separation near the base and should aid the accuracy problem. Brownells, Midway, etc have the tools.
     
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  14. timotheius

    timotheius Active Member

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    I already have a sinclair bump gage....I just now ordered an insert for .270
     
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