Pressure vs. Velocity - URGENT

Discussion in 'The Ammo & Reloading Forum' started by .308 shooter, May 1, 2009.

  1. .308 shooter

    .308 shooter New Member

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    I've posted this to a couple private messages, so sorry if this is repetitive to a couple of you.

    I'm loading some new .308 loads. I'm having problems with excessive bullet drop. The ballistic charts show approx. 2" drop from 100 to 200 and 8" from 200-300. I'm getting approximately a 5" drop from 100 to 200 yards.

    I'm checking velocity through the chrono tomorrow (Sat) - so hopefully I get a response fairly quickly.

    My question - If I load the the maximum charge per the Hornady manual and my velocities are still lower than the published velocities for the powder and bullet I'm using, will it hurt to go higher? I know to watch for signs of high pressure, but was wondering is velocity and pressure proportionate?
  2. gdmoody

    gdmoody Moderator Supporting Member

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    I personally do not recommend going higher that the charts say. There is a reason that that the charts are there. I would think that after a certain level the pressures could get dangerous very quickly. I am not an expert in any shape, form, or fashion, but I say that safety for yourself and those around you is more important than a few inches of bullet drop.

    This is just my two cents worth.
  3. Haligan

    Haligan Well-Known Member

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    One thing, when you view the charts and see the publshed velocities, you have to consider the barrel they were shot out of. If it was a test barrel, if it was x type rifle, or type y.

    You do what you want, but I would not exceed max loads.

    The thing here to watch out for is the sudden spike in pressure, (usually associated with compressed charges)(but not always)
    In other words you'll be going along all fine and dandy .10 grain higher, .20 grain higher, then somewhere about .26 grain higher then recommended you reach a pressure point you didn't expect.
    Like I said you do what you want but if your within min and max charges, I don't think powder charge is the source of you drop descriptions.
  4. .308 shooter

    .308 shooter New Member

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    Thanks for the quick response. I went ahead and loaded while waiting on answers. I guess I'm a chicken (or just smarter than I want to be). I'm not even going up to the max charge. I'm staying about 1 grain away from the max charge. I'll see what the chrono says just out of curiosity and let the drop "fall" where it may. As long as I'm grouping decently, I guess it doesn't matter.

    Thanks again.
  5. islenos

    islenos New Member

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    The max in the chart is not the max for the load. Everything in this world is underrated for consumer protection. Reloading book tend to vary so there is nothing set in concrete. Now the reason for underrating is that too many will exceed the max just to see if they can blow something up.

    If you have no bulging in the brass, primers aren't popping out and shell aren't hard to extract, then there shouldn't be a problem.

    Now, if you blow up your rifle and want to bring a lawsuit against me, my information is as follows:

    Barrack Obama
    1600 Pennsylvania Ave
    District of Columbia
  6. 308 at my gate

    308 at my gate New Member

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    You are smart for waiting to see what the chronoghraph read out is. If the velocities are way down then you need to look at variables like brass, powder, barrel length, and even primers. You might even try a different load with different powder and all the before mentioned. Maybe something is not marked correctly or something is not what it says it is. You could try the load in a different rifle and see if it still does the same thing. I myself do not mind using the max load in the reloading manuals but I do not exceed them. I have a Rem 308 PSS that I chronographed loads for so that I could predict bullet drop at 500 yards.
  7. .308 shooter

    .308 shooter New Member

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    - ----- So you're the reason I can't find any ammo - Thanks alot:):)

    The variation in books and the bullet drop is why I'm asking the questions. - I've blown the gun out once and don't want to do it again....

    Thanks guys....
  8. Tony22-250

    Tony22-250 New Member

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    I shot a HOT loaded .308 out of a Remington 700 and it kicked like a 30-06 and I'm like what the !@#$ I than ejected the shell and to my horror only half of the .308 shell came out it looked like I ejected a .40 S&W or a 10mm hand gun round........ but luckily we got it out using a small screwdriver and a cleaning rod and no damage was done to the gun.
  9. LDBennett

    LDBennett Well-Known Member

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    Tony was lucky! Sometimes nothing short of tapping the remaining case and pulling it out with the tap works. Working the forbidden pressure area is not recommended but everyone tries it at least once. Some win, some don't.

    LDBennett
  10. JLA

    JLA Well-Known Member

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    Ill be the first to admit i ventured so far into the forbidden pressure range I bulged the barrel on a ruger .44 mag... I rarely exceed starting charges nowadays finding my favorite load (and just so happens to be my most accurate) is 15.7 gr. of blue dot under a 240 gr. lead hardcast bullet in my .44 mag.

    Just wondering, what rifle are you firing your reloads from.
  11. cycloneman

    cycloneman Well-Known Member

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    We need to know how long your bbl is. Are you using an autoloader or bolt action? What is your velocity? What wt bullet are you shooting and what charge did you develop? Need all this to be able to help you.

    Come on Chrony. Well be waiting:)
  12. 312shooter

    312shooter Active Member

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    What basis are you finding this bullet drop? Not to be a smart a** but did you sight in on another load ex. 150gr bullet and different powder then your 168gr is shooting lower? Or did you actually fire this round at targets from 25,50,100 yds etc. and map out the bullet drop. Details will get us the answer.
  13. .308 shooter

    .308 shooter New Member

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    Thanks to all. I'm shooting a Savage 10FP bolt action .308. w/ 24" barrel. I'm basing my bullet drop from my first experience.. Seems when first shooting I could zero at 100 and use my BDC reticle for the 200 yd mark. Started reloading and it's considerably off now, even with factory ammo.

    I'm shooting both 168 and 150 grain at different times. I adjust the zero each time for which ever weight I'm shooting. I'm trying different rounds to find my favorite.

    I've been in touch with someone using a ballistics calculator and my results are typical so I don't think I'm as far off as I thought. I'm forgetting about the drop and going for accuracy and let ehe drop "fall" where it may.

    Thanks for all your help everyone.......
  14. Haligan

    Haligan Well-Known Member

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    Are you sure your scope isn't loosening up on you ? Or mabe the scope is creeping in the rings from the recoil ?
  15. .308 shooter

    .308 shooter New Member

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    Yep.... I've checked the scope and it's secure. I do have to check the alignment/levelness, but I'm sure it's secure.
  16. JLA

    JLA Well-Known Member

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    how hot are your loads? Bullet drop compounds as velocity decreases, also the vertical window of your bullets trajectory is going to be greater at lower velocities. Thats why they call the ol' .45/70 a rainbow cartridge... large heavy chunk of lead at 1800 fps doesnt lend itself well to flat trajectories. The problems you are experiencing sound to me like your velocity is low. perhaps a bit too low for the ballistics information to make sense. do you have a chronograph, or acess to one?
  17. 10 Spot Terminator

    10 Spot Terminator New Member

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    Seeing as to how you have pretty much eliminated such things as scope shift , action screws all tight etc. , then the chronograph should help you work through your load workups. The one thing that has come to light for me in the past couple of years when it comes to initial powder and bullet combos to start off with is powder burn rates in conjunction with barrel length "and" bullet weights tend to help get me on track faster . When selecting from the powders listed for a particular weight bullet I tend to lean toward 2 things,,, slightly slower powders for long barrels say 26 in. or longer and slightly faster for 22 in. and shorter as to optimize the powder being burned by the time the bullet leaves the barrell. My other primary consideration is the density of the proposed powders in so far as to how much they fill the case . A full or nearly full case of powder with the optimum burn rate has proven for me to get me on track faster. From there on the chrony will help denote if there is any pressure spiking as your loads get progressively hotter the extreme spread in fps will jump . If you get the speed you need and short deviation in fps along with the accuracy then you are home free. If the accuracy is close to what you are looking for but would like better then try adjusting your bullet seating depth as often that is the final touch. Changing primers too can be the last step but reduce your loads and work back up to the top.Enjoy the ride and here is hoping you find those sweetheart loads . 10 Spot
    Last edited: May 6, 2009
  18. JLA

    JLA Well-Known Member

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    10 spot on advice;)
  19. LASIE

    LASIE New Member

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    thanks to all the lawyers.
    any of the old fellows here can tell you that the reloading books from the early 60's had much higher or hoter loads in them than all of your newer ones do now so don't be afraid to go above the max in a new book.
    every gun will not be the same so if you know what to look for you are safe.
    I read that a guy had a friend of his that shot a 308 in his 25-06 and it did not hurt him or the gun. the rifle just happened to be a savage 110 rifle.
    the design of all rifles are tested for 2 times the pressure of the load they are built for liablity reasons.
  20. woolleyworm

    woolleyworm Active Member

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    The chrony will tell the tale. Also curious as to which ballistics chart you're using. Hope you get it worked out, good luck !

    and BTW.... very few, if any of the "old fellows" here are going to "tell someone not to be afraid to go over max loads from a new book" They may tell stories about doing it and that the old manuals are "hotter" than the new, but we're all a wee bit smarter than to encourage someone that we don't really "know" to go "hot".
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