how to reduce velocity extreme spread?

Discussion in 'Reloading' started by rufous, Jun 9, 2008.

  1. rufous

    rufous Well-Known Member

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    I am hoping some one can advise me on how to attempt to reduce my extreme spreads in velocity. Right now I am shooting my 300 Win Mag and I am using F215M primers and Ramshot Magnum powder. Thanks, Brian.
     
  2. boomtube

    boomtube Well-Known Member

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    So, what is your current average velocity, E.S. and S.D.?

    How far off the lands are you?

    How many times has your brass been fired?

    Are you FL or neck sizing?

    Are you crimping the bullets?

    Do you have other loads for that rifle that do better, and, if so, what are they?
     

  3. rufous

    rufous Well-Known Member

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    My average velocity for 12 shots fired is 2960 (out of a Broughton 25" 5C land) and the extreme spread was 50. I did not check SD. I am 0.020" off the lands as that seems best for accuracy. This brass has been fired 4 times and I am FL sizing but minimally, still headspacing off of the shoulder. I am not crimping and other loads have similar velocity spreads. Bruin.
     
  4. ackleyfan

    ackleyfan Well-Known Member

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    Try, RL22
    H1000
    or Imr 4831!
     
  5. Marine sniper

    Marine sniper Well-Known Member

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    A lot of it is in brass prep, do you neck turn the brass ? you need to, trim them all to the same length ? do that also, clean and prep primer pockets inside and out, neck size only (only need about .001 neck tension) clean the inside of the neck when you are done with the above, some guys polish the inside of the necks with steel wool, I clean with carb cleaner and toilet paper.

    If you go to a little more extreme you can weigh the brass, of course use the same manufacture for all the brass.
     
  6. boomtube

    boomtube Well-Known Member

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    Okay. Sounds like you are doing everything right.

    An ES of 50 fps at that speed sounds quite good to me. It's hard to get below that and it really won't make any noticable difference in the field if you do. If the accuracy is good I'd smile and use it!
     
  7. goodgrouper

    goodgrouper Well-Known Member

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    The easiest way to change the ES is to change the powder charge!!!!! Go up and down of your current load by .5 grain increments and it will change the ES and SD. Look for the low load node and the upper high node. Graph them out and see if the gun likes that powder. If not, try another powder. It's that easy!
     
  8. goodgrouper

    goodgrouper Well-Known Member

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    Whoa. I disagree. For long range shooting or hunting, an ES of 50 would not be acceptable to me. You would be asking for big time vertical dispersion at distance!

    I like to get my SD down into the single digits and the ES around 20 fps or less. Not only will this be a better long range combination, these numbers will be a result of a load that is burning efficiently and will be much more dependable day in and day out.
     
  9. royinidaho

    royinidaho Writers Guild

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    Roger what GG said!

    I've had good luck with heavy for bore bullets using US-869. That is, 300 SMK in a 338 RUM @27xx FPS ES = 1 for 6 shots.

    However, same load w/265 gr bullets wasn't that good. Thus the heavy for bore consideration.
     
  10. rufous

    rufous Well-Known Member

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    Thanks guys for the tips. I will try another 0.5 grains of this powder to see if accuracy is better and if the velocity spread is lower. If not maybe I will try H1000 or RL25. Brian.
     
  11. davewilson

    davewilson Well-Known Member

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    the suggestion for powder was RL22, not 25. if you can't get a 300WM to shoot with RL22 or 4831, it probably won't shoot with anything.

    after 4 firings, it would probably help to anneal the necks.
     
    Last edited: Jun 11, 2008
  12. rufous

    rufous Well-Known Member

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    I have had good results with RL22 in this barrel and the previous barrel but when using 180 grain bullets. I just figured I would use the slower burning powders for the heavier 200 grain bullet, thinking that I could possibly get a bit more velocity at a lower pressure. Is that not proper thinking? Is there something wrong with using RL25 with the 200 grain bullets?

    By the way this rifle is my pack up the mountains big game rifle. As such it has a sporter style Rimrock synthetic stock and a Leupold VX3 3.5-10 scope with the Boone and Crocket reticle. It weighs 9.3#. It is not a heavy bench gun. I can quite consistently get sub 2" groups (3 shot groups) at 250 yards which is the distance at which I zero my main crosshair.

    The load mentioned earlier of using Ramshot Magnum to get an average velocity of 2960 gave me a 1.58" and a 1.41" group at 250 yards. That is about all I can do with this gun. I have occasionally gotten smaller groups but this is pretty standard. Still I would be happy to reduce my extreme velocity spread. I very seriously doubt that I would take a shot beyond 600 yards but would feel more confident if the high and low velocities were closer to the average.

    I have never annealed a case neck. Can someone recommend a product for me to use? I think I remember hearing that Hornady is making one that works pretty simply. Thanks, Brian.
     
  13. biggrizz408

    biggrizz408 Well-Known Member

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    I use 72grs of RL22 in my 300 win mag with a 180gr Nosler accubond and it is grouping right at an inch at 200yds seated .010 off the rifling.
     
  14. boomtube

    boomtube Well-Known Member

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    goodgroup: "Whoa. I disagree. For long range shooting or hunting, an ES of 50 would not be acceptable to me. You would be asking for big time vertical dispersion at distance!"

    No argument on the value of an ES of 2 or less but as a percentage of the speed, 50 isn't bad. That varation, taken alone, won't prevent many hits at any range, IMHO.

    Consider a 7 Mag shooting a .534 Hornady SPBT at a specific speed ( ie, not an average) of 3,100 fps and zeroed at 500 yards. That's a pretty fair long range load. Hornady's #4 book of charts says it will drop 17.1" at 600 yards. Then, at 3,000 fps (100 fps slower) the same bullet expects to drop 18.4" at 600 yards, a full 1.3" difference.

    An ES of half that velocity difference (50 fps) would only cut the drop to something like 7/8"? If even that estimation is off by a half inch, it's certainly not enough to cause a miss on a 600 yd. p' dog! And all that calculating assumes zero wind and mirage to make aiming harder and assumes each bullet is cutting one hole groups out to infinity, none of which is likely in my world!

    I think an accurate, reliable load with an ES of 50, varying only 25 fps from the middle speed, is a pretty good load in the real world.

    Not perfect, but pretty good. :D
     
    Last edited: Jun 13, 2008