Acceptable FPS spread

Discussion in 'Reloading' started by muzhunter, Jan 31, 2011.

  1. muzhunter

    muzhunter New Member

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    Nov 8, 2009
    Just got a new Chrony! Went and check the velocity on my 300 WBY. What would be considered ok FPS spread? Mine came in at 60 FPS this was a 10 shot group. All brass was processed normally. No sorting by head stamp or weight just resize trim to length and go.

    Thanks in advance Muzhunter
     
  2. J E Custom

    J E Custom Well-Known Member

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    I like to get less than 20 to 30 ft/sec Extreme spread and Standard deviations of under 10.
    10 to 15 is good for SDs.

    These are not easy to get but are possible.

    For 100 to 200 yards 60ft/sec will work but when you extend the range you will need to
    improve it to prevent vertical stringing.

    If you shoot 10 rounds in a row (Without Cooling between shots) make sure that the round
    doesent stay in the chamber long (Cooking) before shooting it.

    J E CUSTOM
     

  3. JUDD

    JUDD Well-Known Member

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    I agree with the above...We shoot for single digits on our LR rifles.
     
  4. RockZ

    RockZ Well-Known Member

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    I look for an ES of 10 or less.
    At long range a big spread will show lots of vertical.
     
  5. Trickymissfit

    Trickymissfit Well-Known Member

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    the big Weatherby case likes heavy dense loads, and that may be part of your problem. Also you didn't say how you had the chronograph setup. The muzzel blast from a .300 WBY. is fierce! If the screens are moving from the blast you may well be getting a variation from that alone. A good test would be to move the chrongraph down range another ten feet. If you see the same variation then you know it's in the actually rounds themselves. What is you load data?
    gary
     
  6. JARHEAD1371

    JARHEAD1371 Well-Known Member

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    Don't get too wrapped up in what your chrony spits out at you. I was solely looking at the numbers when I was load developing my 7 SAUM. I ended up wasting time and components. If a load shoots good groups at 800+ yds then your fps spread is going to be low. IMO use your Chrony to get an estimate on your velocity, and your groups to choose a load. Good luck.
     
  7. muzhunter

    muzhunter New Member

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    My load is 180gr hornady interbond, 85 gr IMR7828 SSC. I did not notice the chrony moving after the shot. I would shot 3 then let cool for awhile then repeat.

    I always get groups under an inch at 100yd. Here is a copy of the data.

    If I could attribute the one flyer to a special cause it would shrink the STDEV to 11.0.
    I don't feel good throwing it out

    180gr / 85.0 IMR7828

    3348
    3343
    3352
    3351
    3377
    3352
    3347
    3335
    3356
    3397

    AVG 3355.8
    STDEV 18.05424
    MAX 3397
    MIN 3335


     
  8. Trickymissfit

    Trickymissfit Well-Known Member

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    you have three loads that come into question. The 3377fps and the 3397fps loads along with the 3335fps. How are you measuring the powder in your loads? Also what is the variation in the seating depth?
    gary
     
  9. Reloader222

    Reloader222 Well-Known Member

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    Getting SD below 10fps is always extremely good. However, below 20fps SD could still be regarded as OK. Low SD does not necessarily implies a good grouping. It all depends on the rifles "sweet spot". Low SD is therefor a helpful guide, but not the overriding factor.
     
  10. muzhunter

    muzhunter New Member

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    The seating depth is per the listed COL in the manual. WBY needs free bore. So all loads are to that length. Each load is trickled to target.

    Another thing concerning to me is the FPS which is way high for a 300 WBY 3355! Fasted list in the manual is about 3200 FPS for a 84.5 load. I could have a fast barrel it is a Pacnor select match grade 26 inch, if that is what they are called. It was their best barrel available.

    I think I will drop it back down in half grain increments and see if it will tighten up some. I guess i have more work to do.

    Thanks for all the info!

    Muzhunter
     
  11. Trickymissfit

    Trickymissfit Well-Known Member

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    pay very close attention to the starting loads in the manual! These are the absolute minimum for a big case like this! Those cases want to be loaded kinda hot. What I would do is to shorten the loaded length about .025" (check with a gauge at the ogive). As for the velocity, I think you need to find another chronograph to shoot thru. Then see if there are any differences
    gary