Pressure vs. Velocity - URGENT

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

  1. .308 shooter

    .308 shooter Member

    May 3, 2008
    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

    Sep 7, 2007
    Athens, Georgia
    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

    Feb 25, 2008
    FEMA Region II
    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 Member

    May 3, 2008
    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

    Mar 16, 2004
    West Texas
    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

    Dec 6, 2008
    Lost in SW USA.
    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 Member

    May 3, 2008
    - ----- 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

    Jan 9, 2009
    Snellville, GA
    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

    Dec 20, 2003
    Hesperia, CA
    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.

  10. JLA

    JLA Well-Known Member

    Feb 26, 2007
    Heart Of Texas
    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

    Dec 16, 2008
    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 Well-Known Member

    Mar 17, 2008
    Las Vegas NV
    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 Member

    May 3, 2008
    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

    Feb 25, 2008
    FEMA Region II
    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 Member

    May 3, 2008
    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.
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