Possible causes of high ES...STILL HIGH

Discussion in 'Reloading' started by buckbrush, Oct 9, 2011.

  1. buckbrush

    buckbrush Well-Known Member

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    I've been working up loads for a 7 RUM. I am getting ES numbers of 50-60 with both bullets I have tried. Powder is Retumbo and primers are CCI250's. I've never had this issue before. Any help is appreciated.

    Thanks.

    Tried US869 and it's worse. Up to 80 fps.
     
    Last edited: Oct 16, 2011
  2. RockZ

    RockZ Well-Known Member

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    Re: Possible causes of high ES

    How many different powder charges did you chrono?
    Finding a powder charge with a low ES is the key, and is the biggest determining factor in establishing a good ES.
    Also you may want to try US869,( it's a fine ball powder), if you can't get results with retumbo.
    Sometimes you can get a powder bridging in the neck of high capacity small caliber cases with large extruded powder and that causes lots of problems, including High ES as well as pressure spikes.
     

  3. Dano1

    Dano1 Well-Known Member

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    Re: Possible causes of high ES

    RockZ is right on. Stick powders in such over bore cartridges are very prone to bridging int he case neck. Unfortunately Ball powders are the way to go here. While I don't have a 7RUM, I'm shooting a 7STW and have had similar issues with Retumbo, a 7 RUM has to be worse....LOL.

    There are those out there who say that US869 isn't temp stable like Hodgdon has claimed. So far I haven't seen the diffrence. You should get better velocities with US869 Anyway. Vihtavori 20N29 is the only powder I know of that is slower and still a ball powder (I think). Load density seems to be optimum for these types of cases as well.

    Dan
     
  4. buckbrush

    buckbrush Well-Known Member

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    Re: Possible causes of high ES

    When you say bridging, do you mean that the powder is "clogging" in the neck?

    Thanks.
     
  5. RockZ

    RockZ Well-Known Member

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  6. buckbrush

    buckbrush Well-Known Member

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    US869 was worse. Could this be a barrel issue?
     
  7. bigngreen

    bigngreen Well-Known Member

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    I found lighting Retumbo with Fed 215 got me better results due to getting it lit a little better.
     
  8. Dano1

    Dano1 Well-Known Member

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    At this point I'd go back to basics as US869 should NOT be worse than Retumbo. 50-60 extreme spread could be other things, like diffrence in brass thickness from case to case. If all case prep has been done precisely and you have sorted brass to form a control group and still having 50-60 extreme spread, you are closer.

    I would also look at copper fouling, (Is this a factory gun???). High velocity 7mms are very prone to copper fouling. And Factory barrels are certainly not the smoothest. Are there imperfections, like tooling marks or burs?? One would think that It's not a big deal, but it really can be.

    I actually had a 7mm Rem Mag in a Sendero that had a tight barrel. It was accurate enough, but ran 200fps slower than 3 other 7mm Rem Mags that I Chronyed on the same day with the same load. It ended up having a tight barrel by a few Thousandths.

    You have mentioned Extreme spreads, but how is the accuracy?? ES aren't a big deal unless the accuracy isn't there..and if shooting at reasonable ranges. Are you trying to make this a target rifle or just hunting? I'm not trying to tell you to settle, but you need to realize the limits of a factory rifle.

    You can lap the barrel to smooth it out, either by fire lapping (last resort) or hand lapping with a tight jag and lots of elbow grease. (I did this for the Sendero and it helped with the ES for that rifle by dropping it from 70-80 to 40-50FPS, It was a marked improvement.) Copper fouling was also reduced.

    I hope I'm being helpful, Just trying to think of diffrent ideas.

    Dan
     
  9. backwoods83

    backwoods83 Well-Known Member

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    Neck tension and primers. Try to make sure the resistance feels the same when seating the bullets, you may also want to try CCI BR2, Fed210M, or WLRM primers, sometimes cci250s or 215s are to errattic.
     
  10. MSLRHunter

    MSLRHunter Well-Known Member

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    I have always had trouble with ES with retumbo in 2 different calibers. I switched to H1000 and my ES shrunk to 10-15 fps, which is good enough for me!