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.270 velocity variations

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  #15  
Unread 12-10-2009, 12:28 PM
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Re: .270 velocity variations

You may want to focus more on conditional/technique issues, such as direct sunlight on your chrony, angle of sun, is the sky overcast, is your barrel clean?, barrel cooling?, quality of the chronograph, temp/humidity conditions, are you firing directly thru the middle of the uprights each time?, case length and capacity, are you close to or touching the lands?, powder/primer type of course, eventually you will narrow it down.
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  •   #16  
    Unread 12-10-2009, 02:57 PM
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    Re: .270 velocity variations

    +/- .1 or even .2 grains is NOT going to change velocities by 100 FPS!

    Think that through...We push powders up 5-6 grains to get that much velocity increase quite often!

    Thus, I doubt that it is the scale, but borrowing a quality lab scale to give you some peace of mind about it isn't a bad idea.

    I found that my velocity variations DROPPED significantly when I started using a Chargemaster vs. a beam scale. Beam scales can be very accurate, IF everything is perfect and consistent, but most guys using a beam scale will be NO more accurate than a Chargemaster. Beam scales are very dependent on you having a view of the scale that is consistent charge to charge, and most guys aren't good at that! (To achieve best accuracy, you should have a perpindicular view of the beam, and most reloaders don't do that, because it requires getting the scale to eye level, or bending down to it. Try bending to the same exact spot 10 times, much less the 100 or more that most reloaders use each time!)

    I have fiddled with my Chargemaster, and it is faster than it was from the factory, and I haven't seen an great degradation in accuracy.

    Large extruded powders don't meter quite as well as fine powders like Xterminator or TAC, but the soda pop straw trick helps with that issue, too.

    I think there is something more significant than simply the powder charge causing that kind of variation!

    BTW, my 7mm WSM varies less than 20 FPS with a WHOLE GRAIN of H1000 at 2930 and 2950 FPS between 64 and 65 grains. 66 grains pushes it only to 2960-2965 FPS.

    Look elsewhere first, once you have convinced yourself that the scale isn't grossly off!


    Bill
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    http://waitesandbalances.blogspot.com/
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      #17  
    Unread 12-10-2009, 03:35 PM
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    Join Date: Mar 2008
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    Re: .270 velocity variations

    Thanks,
    In my earlier posts I mentioned that I have access to a pharmaceutical grade scale that weighs out to .0000. I was a chemistry major way back when and I cut my teeth on beam scales. Everything you said about using the beam scale is %100 right on. I trust digital!!!
    I am going to throw some different charges and have them checked. Have to wait until next Tue....going out of town. I will let you know.
    I AM going to figure this out.
    Thanks
    Ken
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      #18  
    Unread 12-10-2009, 03:37 PM
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    Join Date: Aug 2009
    Location: Carlisle, PA
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    Re: .270 velocity variations

    Quote:
    Originally Posted by bwaites View Post
    +/- .1 or even .2 grains is NOT going to change velocities by 100 FPS!

    Think that through...We push powders up 5-6 grains to get that much velocity increase quite often!

    Thus, I doubt that it is the scale, but borrowing a quality lab scale to give you some peace of mind about it isn't a bad idea.

    I found that my velocity variations DROPPED significantly when I started using a Chargemaster vs. a beam scale. Beam scales can be very accurate, IF everything is perfect and consistent, but most guys using a beam scale will be NO more accurate than a Chargemaster. Beam scales are very dependent on you having a view of the scale that is consistent charge to charge, and most guys aren't good at that! (To achieve best accuracy, you should have a perpindicular view of the beam, and most reloaders don't do that, because it requires getting the scale to eye level, or bending down to it. Try bending to the same exact spot 10 times, much less the 100 or more that most reloaders use each time!)
    That is why mine is on a shelf at eye level. Works great.

    Quote:

    I have fiddled with my Chargemaster, and it is faster than it was from the factory, and I haven't seen an great degradation in accuracy.

    Large extruded powders don't meter quite as well as fine powders like Xterminator or TAC, but the soda pop straw trick helps with that issue, too.

    I think there is something more significant than simply the powder charge causing that kind of variation!

    BTW, my 7mm WSM varies less than 20 FPS with a WHOLE GRAIN of H1000 at 2930 and 2950 FPS between 64 and 65 grains. 66 grains pushes it only to 2960-2965 FPS.

    Look elsewhere first, once you have convinced yourself that the scale isn't grossly off!


    Bill
    You make some good points.

    Fitch
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      #19  
    Unread 12-10-2009, 03:54 PM
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    Join Date: Oct 2008
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    Re: .270 velocity variations

    Haven't heard about the soda pop straw thing. Please describe
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      #20  
    Unread 12-11-2009, 03:47 PM
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    Join Date: Feb 2005
    Location: USA
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    Re: .270 velocity variations

    Consistent neck tension is esenticail for low extreme spreads, also the best time to chrono loads is on over cast days.

    I really like H-1000 for consistency
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    Last edited by jwp475; 12-13-2009 at 07:54 PM.
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      #21  
    Unread 12-13-2009, 07:45 PM
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    Join Date: Jun 2007
    Location: Central Washington
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    Re: .270 velocity variations

    Quote:
    Originally Posted by nheninge View Post
    Haven't heard about the soda pop straw thing. Please describe
    Take a McDonalds straw, (they are almost perfectly sized to do this, most straws are too small), cut a small piece, and insert it into the end of the dispensing tube. Most people find a small piece of duct tape or medical tape is helpful in keeping it in place.

    Since the straw is slicker than the metal tube with threads, not as much powder climbs the side and there is less chance it will fall into the tray and upset your measurement.

    Hope that helps!!

    Bill
    __________________

    The strongest reason for the people to retain the right to keep and bear arms is, as a last resort, to protect themselves against tyranny in government.

    Thomas Jefferson

    http://waitesandbalances.blogspot.com/
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