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Acceptable FPS spread

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  #1  
Unread 01-31-2011, 07:32 AM
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Acceptable FPS spread

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
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  •   #2  
    Unread 01-31-2011, 08:19 AM
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    Re: Acceptable FPS spread

    Quote:
    Originally Posted by muzhunter View Post
    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
    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.

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      #3  
    Unread 01-31-2011, 08:40 AM
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    Re: Acceptable FPS spread

    I agree with the above...We shoot for single digits on our LR rifles.
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      #4  
    Unread 01-31-2011, 08:45 AM
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    Re: Acceptable FPS spread

    I look for an ES of 10 or less.
    At long range a big spread will show lots of vertical.
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      #5  
    Unread 01-31-2011, 10:27 AM
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    Re: Acceptable FPS spread

    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
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      #6  
    Unread 01-31-2011, 11:44 AM
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    Re: Acceptable FPS spread

    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.
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      #7  
    Unread 01-31-2011, 03:43 PM
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    Re: Acceptable FPS spread

    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


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