velocity spreed

Discussion in 'Rifles, Bullets, Barrels & Ballistics' started by retiredcpo, Feb 4, 2011.

  1. retiredcpo

    retiredcpo Well-Known Member

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    OK Im new to this whole chrono stuff
    I took my new chrono out for a fun day at the range testing and chronoing loads
    my question is if you have a load that shoots reall good Sub moa out to 1000 yards
    but the velocity spread is large 50 fps or larger what can be done to try to tighten this up or should a guy just not worry about
    Maybee I should not have added a chrono to the mix one more thing to mess with my extremly cloudy head.
    thanks
    retiredcpo
     
  2. retiredcpo

    retiredcpo Well-Known Member

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    Forgot to ask how long do you guys wait between shots when working with a chrono
    thanks again
    retiredcpo
     

  3. SBruce

    SBruce Well-Known Member

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    FWIW, in my opinion; if you're perfectly satisfied with sub moa at 1000 yds (as I believe most would be) then don't worry about it. Especially if the groups are minimum vertical spread.

    I've never put a whole lot of faith in chrono's, especially the cheaper ones. I would rather develop a tight load that shoots minimum vertical at long range and then chronograph to get an average velocity. Rather than base my load off the chrono's data.........Just the way I've done it.

    I suppose that maybe some of the high dollar precision units might be useful for load development, but I've never had one of those.

    The most accurate factory barrel rifle I ever laid my hands on was my old 220 Swift Ruger 77. It shot 1/2 minute to 700 yds on calm days and all my load development was without a chrono. In fact, I had nearly 4000 rounds through the gun before I even bought a chrono.

    I am sure some others rely on chrono data and aren't satisfied unless they get small ES and SD #'s.
     
  4. retiredcpo

    retiredcpo Well-Known Member

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    SBruce
    sounds like you do your loads just like we allways have . The Chrono is a good one i believe its a CED M2
    Got it just to know how fast our loads are going for use in Ballistic calculatrrs insteed of guess.
    but now it has us second guess good loads
    With all that said I am not changing loadsv
    just wondering if there was someting minor you could do to improve things
    retiredcpo
     
  5. SBruce

    SBruce Well-Known Member

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    One thing thats real simple and often overlooked is the distance the chrono is to the muzzle.

    Putting it at least 10' away (preferably 12-15') supposedly gives more accurate readings.

    I've also read that varying light conditions will give variable readings (partly cloudy days when it's sunny one shot, cloudy the next).

    I've also read that the chrono need to be very near level with gravity..?

    That's all I can think of without changing primers, or annealing necks, trying different powders, seating depths, ect.

    I always uniform pockets, clean pockets, and de'burr flash holes. I also sort cases for neck thickness and weight. I weigh each powder charge to within .05 grns (according to my scale) and neck size as much as possible. I also trim to uniform lengths and fireform cases in gun before sorting by weight..............sound similar to what you all do?
     
  6. retiredcpo

    retiredcpo Well-Known Member

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    Sbruce
    I unifrom pockets and clean pockets but I do not sort anything
    I use a digital scale and it only goes do to 0.1 but I do not take anythin execpt exactly what im looking for (if im looking for 64 grs I wont use 63.9 or 64.1) I used a very small home made spoon to remove excess and a trickle to add some.
    dont really want to change componants

    I might play with Adding more powder in small increaments and mess with the lenghts alittle
    How much do you think you gain by deburring the flash holes?
    retiredcpo
     
  7. SBruce

    SBruce Well-Known Member

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    I can't honestly say, because I've always just done it:)

    My great uncle was a fairly accomplished benchrest shooter/competitor and taught me how to precision handload (compared to standard reload) a little over 20 years ago. I've used those methods and never strayed for all this time............Oh, one other thing; I also nylon brush the necks inside and fine steel wool the outside to remove the soot/carbon. Just another thing he did, but I doubt it affects accuracy on hunting calibers and chambers enough to ever notice. Flash hole de-burring would probably be more noticeable.
     
  8. retiredcpo

    retiredcpo Well-Known Member

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    I went to the range today I increased my load by 1/2 GR my ES came down to
    22.51FPS and the groups still look good the only issue I have is Im 1/2 gr over the load data max but not showing any signs of presssure
    It was only 50 degrees today may try it again in the summers when its hot.
    retiredcpo
     
  9. RockZ

    RockZ Well-Known Member

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    Re: velocity spread

    Powder charge changes are the biggest determining factor in changing ES/SD.
    All of the other things will fine tune it.

    What cartridge, powder , bullet, oal are you using and what numbers did you get at other powder charges?

    I work up to a max load by using velocity, case head expansion, primer condition, bolt lift,extractor marks or lack thereof. As well as temp, OAL, whether it is on the lands or off and of course published data and my quickload data.

    Sometimes MY max powder charge for a particular combination is well Below book max.
    Case in point was a savage 270wsm. With 140accubonds and imr 7828 I was 2gr below published max as my max in my particular setup. I was well off the lands too!

    Sometimes MY max powder charge for a particular combination is Above published data.
    Especially when I am loading to a much longer and still off of the lands.

    Even different lots of the same powder may have a different max charge. Different case capacities of various brass,primers, etc.

    Every rifle, bullet, powder combination is different.

    I mostly test at 565yds and want a load with a 1.5 inch so of vertical at that distance.

    I guess it was a long winded way of saying to try different powder charges.
    You may find a great load lower or maybe even higher.
    Just stop when you should and don't push it too hard at the top.
    I work up pretty high and I have never had to bang on a bolt to open it or had a primer blow out.
    It looks like you are doing things right, you should be able to bring the es down at least another 10 or more fps.
     
    Last edited: Feb 14, 2011
  10. retiredcpo

    retiredcpo Well-Known Member

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    Rock
    have several loads we are working on the one I have been refering to
    is a 7mm remington mag 160 gr Accubond with 60 grs of 4831sc win brass and primers OAL is 3.375 which is way off the lands now9it will be time for a new barrel next year probably.
    I know this is a good load and a safe one I have been shooting it for over a year now even when it was hot outside pushing 100 degrees.
    I ask the question for two reasons
    1-to try to understand what the chrono data is telling me and how to use it to better my loads
    2- to try to learn what I can do to try to better things with out changing to much
    I may try some lighter loads just to see what happens
    Differant guns are extremly differant
    My 223 load has a SD of 55 FPS Im helping a buddy work up a load for a new gun the same load in his gun has a SD of 8.0 FPS the only diffeance is his is 0.010 shorter. Thats a huge differance for just changing guns
    retirecpo
     
  11. RockZ

    RockZ Well-Known Member

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    You are right.
    It is amazing what differences there are in loads and different rifles!

    I'm sure you can reduce your spread by working up.
    It looks like you are well off the max load for the 160AB and 60gr of H4831SC.
    At 60gr you are getting a low fill rate as well
    I checked some numbers :
    With your oal Quickload gave me a max of 67gr.
    Hodgdon gave 64 gr for 162gr HDY SPBT
    Sierra gave 63.6gr with their 160gr bullets.
    I read online that Nosler max was 65.0, but don't have their manual so can't confirm.

    Of course these numbers are just a guide, but they do suggest you have plenty of room.

    I would suggest to work up in .5 grain increments over the chrono.
    You should find a load as you work up that will offer a lower es/sd.
    It may even be in the 63.5 range, but work up slow as you have been doing and you should find it.

    Don't let the 100yd accuracy get you stuck on a load.
    Unless you are getting very little vertical at long range.

    If you are shooting 2" groups at 600yds , the load is fine!

    Then it could be a chrono issue as mentioned before.

    I have a load that puts 3 bullets in the same hole at 100yds. But has an ES of 40 and shoots a huge vertical at 600yds.

    My load with the least ES, 9 fps, is 3.5 grains higher and is nearly at my max.
    And only has 1.5" vertical or less at 565yds.

    I think you will have great results as you work up.
     
  12. retiredcpo

    retiredcpo Well-Known Member

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    Rock
    Thanks so much for the info
    I may work this load alittle more but I think i would prefer to do it when its hotter outside
    Im fearfull of working up a lot in the cold then shooting in the summer way to hot.
    but it gives me something to do between vamit hunting and deer hunting.
    The case are not very full with this load.
    retiredcpo
     
  13. MontanaRifleman

    MontanaRifleman Well-Known Member

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    I have a 1 yr old Chrony Alpha and a 20 yr old abused Shooting Chrony. When I set them up back to back, they are anywhere from 5 fps to 60 fps different with no consistancy in the difference. That was a real eye opener. I "think" the 20 yr old Shooting Chrony is actually more accurate. I'll be getting a CED M2 soon and shoot all three of them back to back to get a better idea of what's going on.

    That being said, I think chronys are useful tools, but I don't beleive them 100%. I consider their info to be relative and not absolute.

    Some good tips and advise on reloading, etc... and if you're getting consistant sub MOA @ 1K, I would say that was pretty good.

    -Mark

    Edit: I have also seen very significant swings (close to 100 fps) from morning to afternoon to evening and cloudy vs sunny FWIW
     
    Last edited: Feb 14, 2011