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Yup - I got my very own chrono

Discussion in 'Ammunition & Reloading' started by tlfreek, May 26, 2016.

  1. tlfreek

    tlfreek Vancouver WA Active Member

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    Hi i am for the first time in my reloading career looking at how my projectiles perform using a chrono and what I am finding is not what I expected. It seems that the performance of the projectiles are several hundred fps than what is listed on the Accurate LT-32 loading data - I know there are many factors that could attribute to this, but knowing what the projectile does at almost max loads do you ever push the max to reach fps? I have never done this (cause I've never had a chrono) but curious if you ever formulate your own recipe based upon how the gun (in this case rifle) shoots.

    Ruger Precision Rifle 308
    All are using CCI primers and Hornady brass and Hornady projectiles.

    Example

    Lower End:
    1 (168 grn HPBT) 33.7 grains of LT-32 me -> 2083 - Accurate LoadData -> 2349 (at 33.7)
    2 (168 grn HPBT) 33.7 grains of LT-32 me -> 2183 - Accurate LoadData -> 2349 (at 33.7)

    Upper End:
    1 (168 grn HPBT) 37.3 grains of LT-32 me -> 2388 - Accurate LoadData -> 2555 (at 37.5)
    2 (168 grn HPBT) 37.3 grains of LT-32 me -> 2372 - Accurate LoadData -> 2555 (at 37.5)

    Thanks.
     
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  2. Benchrest

    Benchrest The Desert Planet Well-Known Member

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    Simple answer: No.

    Don't go under minimum, and approach max with caution.
     
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  3. deadeye

    deadeye Albany,OR. Moderator Staff Member

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    What firearm and length of barrel were they using to acquire their data, this can easily be the difference. Never load to max or above to get a certain fps, your firearm may not take the pressure that can be produced. You should always load to the specific firearm and how it best performs (accuracy) that is not always at the high end. The powder used will also have a different result in different firearms, yours may shoot great with "X" grains but another will have bad consistency.
     
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  4. Dyjital

    Dyjital Albany, Ore Flavorite Member Bronze Supporter

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    90% of the loads I've made that are the most accurate are the near middle of the road for loadings.

    Different rifles will shoot the same load differently with velocities.
     
  5. P7id10T

    P7id10T Cedar Hills Bronze Supporter Bronze Supporter

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    Ideally you work up a whole batch of loads to test. I've read about guys loading every .3 grain and getting very anal about 0.1 grain difference.
    What I've experienced is doing 1/2 grain increments works well, and 0.2 gr didn't make much difference, but I'm talking about loads from 70-95 grains.
    I'll start at low range, do 5 bullets in each 1/2 grain increment, then spend a couple of hours shooting them. My observations:
    1. Seldom did my load tests ever equal the supposed performance of the published recipe.
    2. Usually I would start showing pressure signs ~2 grains below my max loads. I would stop my tests there. Years ago, like a DF, I would continue shooting them, and I've become tired of hammering the bolt open and hammering out a stuck case.
    3. Except for one instance with 7RM, The fastest were never the most accurate.
    4. I never did any ladder tests for barrel harmonics, but I would find powder/bullet nodes where the MV would jump 60-80 FPS and then settle back down. While it intrigued me, I went with it.
    5. Used to always load for OAL where the the bullet was either touching the lands or max 0.010" off. By chance, loaded some that were 0.050 off the lands and they were scary accurate.
    Not meaning to be preachy, just my 2¢.
     
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  6. ron

    ron Vancouver, Washington Silver Supporter Silver Supporter

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    I load for best accuracy. Most powders I
    have tried work best at 5% or so below max load.
    Noticeable exception is VV N140. The closer
    to max load you get the tighter the groups? o_O
    I have never used the AA powders you are using.
    The powders that I have used that give me the best
    results for the 308 are IMR 4064, Varget, VV N140, AA 2520.
    My favorite bullets are 175 SMK. Now I am working
    on Sierra tipped match king bullet loads.
    https://www.sierrabullets.com/store/product.cfm/sn/7775/308-dia-175-gr-Tipped-MatchKing-TMK
    Different bullets, brass, primers, powder, seating depths,
    neck size. Many variables. Good luck, have fun.
     
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  7. Reno911

    Reno911 Hillsboro Well-Known Member 2015 Volunteer 2016 Volunteer

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    Maybe I'm the only nut job here but I have lots of data that shows either powders are better than they were ten to fifteen years ago, or loading manuals have gotten progressively soft on their max powder loads. For a couple of my 155 HPBT loads I'm almost 10% over max data in the Hornady book for RL15 and the Sierra book says I'm only 5% over. However my 15 year old reloading book says I'm 5% under.

    In other words, it's a trial and error thing.
     
    Ura-Ki likes this.
  8. tlfreek

    tlfreek Vancouver WA Active Member

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    This is great information - thanks for the response. My question is what are you looking for? You have to dial the gun in to a certain distance - say 100 yards first right? What do you dial that in with - what ammo what load? - my thoughts are if you use your ladders I think you'll be chasing yourself if you dont have a solid base to move forward from. I could be wrong (did I say i just got a new chrono?).

    I actually worked up a large range of loads in .2 grain increments. I tried shooting them and they were all over the place and speeds (in most cases) decreased as pressure decreased. but from that I have fps data but thats about it.




     
  9. edslhead

    edslhead Vanc Gold Supporter Gold Supporter Silver Supporter Bronze Supporter

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    How accurate are chronographs?

    This is from chuckhawks

    Too often, you'll hear where other people want someone else to tell them what velocities to expect out of their rifle. Perhaps even sillier yet, folks will often bicker because their chrono out of their rifle says one number, but the other fellow's number is 50 or 75 fps different. Well, it should be. Even assuming that rifles, lots of powder, primers, and so forth are all absolutely identical, which they clearly are not, various models of chronographs themselves may vary by up to about 8%. Crude, cheap old chrony's tend to clock slower as time goes by.
     
    Last edited: May 27, 2016
  10. ron

    ron Vancouver, Washington Silver Supporter Silver Supporter

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  11. Benchrest

    Benchrest The Desert Planet Well-Known Member

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    Let's see, variables that contribute to final result:

    Temperature, both ambient and equipment
    Air density
    Barrel length
    Barrel specifics
    Leade
    Chamber dimensions
    Case capacity
    Primer used, primer batch #
    Powder lot #
    Projectile construction variables
    Bullet grip
    Chrono brand, model, and setup
    Knowing percentage 'off' of 'published optimistic number'.

    ...continued on page 2, 3, 4

    As handloaders we don't need to be versed in every variable - the most knowledgeable, with the best instrumentation are capable of only a guess.

    What we must have is a firm grasp of the fundamentals. Follow reputable published data, work up your loads, find your node, and if you're after speed, know when to stop.

    "stopping": 1: You work a load until conditions dictate you settle on, or back down your charge. 2: Accepting capabilities of that load.

    The most dangerous part of reloading is ignorance, either by virtue of the person's situation, or by choice.

    Now, I'm off to workup the next batch of thermonuclear 10mm loads :)
     
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  12. tlfreek

    tlfreek Vancouver WA Active Member

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    I'm not sure where this was going, but I suppose it's useful. I've been reloading for years, i understand the reloading data and know there are a pile of variables that can impact performance (I believe i stated that above) - I just have never taken it to the next level using a chrono. And using a chrono what changes to the recipe you cannot make or can make to build the most accurate round. Perhaps none at all - that's great too.

    to put everyone at rest - I do not exceed the maximum charge or minimum charge, mix powders introduce thermo nuclear technology into my reloading practices, but if it would make my target shooting more accurate I might consider it. I'm just a simple guy curious how best to use a chrono and evaluate the best charge.


     
  13. Benchrest

    Benchrest The Desert Planet Well-Known Member

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    My previous post was a response to the above, wasn't meant to be negative in any way.
     
  14. Benchrest

    Benchrest The Desert Planet Well-Known Member

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    A chrono is a valuable tool that augments a handloaders fundamentals. If basic indicators (reading tea leaves) are telling that a certain pressure point is reached, and the chrono states otherwise, then: There's an issue with the chrono and / or setup; That's the way it is.

    As others have stated, the variance between published and what you're getting isn't out of the norm.

    Stay safe.
     
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  15. P7id10T

    P7id10T Cedar Hills Bronze Supporter Bronze Supporter

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    I think it's more of a "error and trial (lawyer)" thing. Drop your max loads, no one gets blowed-up, and if they go over, it's their responsibility.


     
  16. tlfreek

    tlfreek Vancouver WA Active Member

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    Imagine all the mistakes we make as a people, some struggle and drive through buildings because they thought their car was in R and not D, we need "hot" on beverage labels, signs, cushions and warnings to save us. Knowing that I very much doubt powder companies show the true max load, its most likely the inner band of load range.
     
  17. Benchrest

    Benchrest The Desert Planet Well-Known Member

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    Certainly there's that possibility, and it's one I tend to believe at times. But 'we' always burden the responsibility, and without the benefit of training and costly test equipment we only have published data to rely on - rely on by starting at 'min', and working up.

    As we assume lawyers have driven charges down, there's also the possibility modern testing procedures are reporting the true reality.

    That said, there may be room to exceed (max should be a worst case scenario), and for the educated it should be done cautiously.

    I know I've gone right past book (in very small steps) in the 10mm, and if I get my PT II up and running it'll be interesting what it reports (not that I would consider it definitive).
     
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  18. Dyjital

    Dyjital Albany, Ore Flavorite Member Bronze Supporter

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    I have one rifle 2gr over max. I also have the bullet stretched out .020" away from lands. My fps is at and around book max. No pressure signs.

    Chronograph was helpful in knowing where velocities were approaching terminal.
     
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  19. PaulB47

    PaulB47 Hillsboro Well-Known Member

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    You can get funny readings off a chrono if you don't set it up right. For example, I always try to get it at least 12 feet from the muzzle, otherwise (I believe) it sometimes measures the gas cloud velocity rather than the bullet. Make sure the sun is not shining into your sensors; you might wrap duct tape around them to block it. And make sure your sky screens are not shaded and are uniformly white and bright. Often, with a clear sky, I will simply remove the sky screens and let it see the bullet against the sky; that works pretty well too. One thing I have not got working is the chrono under trees, which is unfortunate because that is where my backyard range is, under trees. :(

    One thing, the older I get, the less I feel the need to push for a max load. The deer won't notice if the bullet is going 100 fps slower, and a nice margin for error is something that is good to have. The barrel will last longer too.
     
  20. tlfreek

    tlfreek Vancouver WA Active Member

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    I use a magneto speed V3 - all of that would be impossible for me.