Reloder 16 Temp sensitivity

Discussion in 'Main Message Board' started by Prose, Oct 15, 2019.

  1. Prose

    Prose

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    shooting a 260 rem. Tested at 60F two weeks ago and 30F yesterday. Loss of 30 FPS. 20 shots at each temp. SD was much wider at the lower temp going from 4 at 60F to about 12 at 30F. Barrel received exact same treatment before hand and both strings shot through two consecutive chronograph each time with consistent results. Same brass.

    What are your thoughts?
     
  2. rardoin

    rardoin Silver $$ Contributor

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    Hmm. I found it to be very consistent shooting in upper 40's in winter to the upper 80's in summer shooting Berger 140's hybrids at 2720's in a 6.5 Creedmoor with srp brass. This was recorded with a Labradar in late 2016 and mid 2017...same lot of powder. The loads were very mild.
     
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  3. Forum Boss

    Forum Boss Administrator

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    Thanks for your information. I have seen the official Reloder 16 Temp testing charts and those showed RL16 powder to be very insensitive to temperature change. However, we were looking primarily at the other end of the spectrum -- from about 55 F ambient to 110 F.

    I doubt many matches would be conducted with 30 deg F conditions. However, this certainly could be encountered during late-season hunts.
     
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  4. Prose

    Prose

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    That's what I was thinking too.
     
  5. swd

    swd Gold $$ Contributor

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    I’ve shot it down around 25-30 degrees and didn’t notice anything odd at a few match’s but I didn’t have a chronograph with me. But it shot normal.
     
  6. Shawnba67

    Shawnba67 Silver $$ Contributor

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    I have always wondered if mild vs hot loads would exhibit more/less effects of temp sensitivity.
     
  7. dmoran

    dmoran Donovan Moran Silver $$ Contributor

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    @Prose
    Since you had an SD of 12-fps with your 2nd string (3x worse then your 1st string), I certainly can believe your two averages could have been extreme as well. An SD of 12-fps is typical of a load that is not in tune, that will have large ES regardless of the powder type. Or of ammo that has poor consistency, do to loading issue or inconsistency in the components used.

    You stated it was from the same brass, so what was different in the loads, to take them from a SD capability of 4 to 12-fps (3x worse)?
    Or could there have been chronograph error?

    If the targets did not match the SD data, then it is likely the velocity data had error. Meaning if the 20-shot string with SD of 4-fps did not yield good accuracy, it would be velocity data error or shooter error. And if the string that had SD of 12-fps had accuracy, the velocity data would have to be in error.

    All powders can yield better or worse sensitivity depending on how well the load is in tune with the rifle - IME.
     
    Last edited: Oct 16, 2019
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  8. fatelvis

    fatelvis Silver $$ Contributor

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    An SD of 12 is considered bad? I didn't realize it indicated that I needed to do more tuning work. I'm not being sarcastic.
     
  9. dmoran

    dmoran Donovan Moran Silver $$ Contributor

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    @fatelvis - everyone's mileage is different, but to me 12 is excessive, under 8 okay, with 4 or under being great.
     
  10. Zero333

    Zero333 Silver $$ Contributor

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    20 shot string with SD of 10 or less is great.

    10 shot string definitely below 8 SD is ideal.

    Not many loads can hold single digit SD with a 20 shot string every time.
     
  11. urbanrifleman

    urbanrifleman Site $$ Sponsor

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    That's not the powder. That's the density change. The air gets thicker as it gets colder outside. The bullet slows down.

    If you add a temp sensitive powder into the mix then the velocity change will be much greater. R16 is not changing much. It has a temp rating of about .1 fps per degree. So, in your case 3 fps is due to the powder, the rest is density.

    If you had been using r15 which has a rating closer to 1. The change would have been ambient change plus about 30 fps from the powder added on.
     
    Last edited: Oct 17, 2019
  12. urbanrifleman

    urbanrifleman Site $$ Sponsor

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    Losing about 1 fps from ambient change is about right. I did a similar test with AR Comp which has the same.1 temp rating and I lost 1 fps from ambient. So, I my case 5 fps is from the powder, and 45 fps from air density.
     
  13. urbanrifleman

    urbanrifleman Site $$ Sponsor

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    Its not the R16 moving the velocity. It is the air. You can see R16 runs about .1 to .15 fps per degree from freezing to 130 degrees plus. And it is flat in the middle.

    1527779052631.png
     
    Last edited: Oct 17, 2019

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