various points of accuracy????

Discussion in 'The Ammo & Reloading Forum' started by .308 shooter, Oct 14, 2008.

  1. .308 shooter

    .308 shooter Member

    May 3, 2008
    I was speaking with a gentleman recently and explaining to him my groups are good, but velocity is low. I have to drop almost 2 lines on my BDC reticle from 100 to 200 yds. I was told though my initial charge (which is low) is good, and it gets worse as I go up, that it will also come into another accurate setting as I continue to go up in charge.

    Is this accurate information? Does accuracy come in, go out and come in again as charges increase?
  2. RodneyJ

    RodneyJ New Member

    Jan 24, 2008
    Houston Texas
    Yes, from what I have read and people I have talked to this is true. I have heard the accuracy settings you are talking about refered to as accuracy nodes. The reason for the accuracy to change is due to harmonics and the bullet leaving the barrel at a different point of the barrel vibration. Form what I have read and those I have talked to at the range you may have 2 to 3 powder charges that will produce good accuracy and as you move away from these points up are down the accuracy will deminish untill you start moving into the next node. I'm sure there are others here that can explain it better than I have but I hope this helps.

  3. .308 shooter

    .308 shooter Member

    May 3, 2008
    Thanks..... That's what I was told as well. Back to the drawing board!!:)
  4. LDBennett

    LDBennett Well-Known Member

    Dec 20, 2003
    Hesperia, CA
    RodneyJ explained it correctly and well. But you may not find a node beyond where you are at now.

    If max or just better velocity is needed then start changing components (like bullet, or powder) and developing a new load. The easiest in your situation might be to stick with the bullet you have selected if it performs terminally as you require and move to a different powder. A review of several manuals may show that a particualr cartridge may have an affinity for one powder over others. Start there first but don't be afraid to try others if you have not met your performance criteria. Finding the "ideal" load is an almost never ending quest as there are so many varibles to manipulate. I loose interest after about two powder choices and compromise my performance criteria as shooting for fun is more interesting to me than testing loads...that's just work to me.

  5. DWARREN123

    DWARREN123 New Member

    Aug 23, 2003
    Bad thing is they will change sometimes with changes in components and you have to start over.
  6. LDBennett

    LDBennett Well-Known Member

    Dec 20, 2003
    Hesperia, CA
  7. .308 shooter

    .308 shooter Member

    May 3, 2008
    Thanks all,
    LD.... it's fun for me too. But i must admit, I find it a challenge to try different things. Who knew.....I always thought I liked taking the easy way out. :) I'm not necessarily looking for more velocity, but I guess I wouldn't mind a 3-4" drop from 100 - 200 yds.... especially since I'm hoping to get to the 600 yd range soon.

    Thanks again everyone.
  8. Falconry

    Falconry New Member

    Dec 1, 2008
    I discovered loading for my 06 that with 165 grain bullets I could get a 5 shot group that I could ALMOST cover with a quarter. That was with 56.4 grains of IMR 4350. Now anything else for loads much hotter or lower opened up my groups noticeably. So I like to think of it as a "cone" where you find the sweet spot for the projo/powder matrix. Some guns DON'T like certain powders and or bullet combinations. So, there is a correlation with powder,bullet and barrel harmonics for sure. My .300 WSM likes H414 and 165 grain bullets too,but didn't like the Barnes TSX as much as the Noslers. Heck it even likes the Hornadys too.
    So, try different powders after doing the manuals research. Barnes actually has a good manual for load information and you don't have to use their bullets. Match bullet length to barrel twist (longer bullets need more twist to stay ballistic).
    I get only 1.75" drop from 100 to 200 yards with my 06 and 1.25 with the 300 so I am curious about what type loads and velocities we are dealing with.
  9. Millwright

    Millwright Well-Known Member

    Jun 30, 2005
    308, You've hit upon the real fun in reloading - internal ballistics !!

    Lots of reasons for what you're observing and an important one is barrel harmonics. Another is velocity. As you increase/decrease powder charges for a given bullet weight you decrease/increase bullet "dwell time" (time its in the barrel). You also influence its spin rate - a factor in stability. Also important to accuracy in a given rifle is how the powder burns - both in rate (speed) and pressure curve development. And all these affect barrel harmonics as well......

    IOW, once you get the addiction, its lifelong as the possibilities are endless and growing..... >MW
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