Powder Throw Just as Significant - Seating Depth

Discussion in 'Reloading' started by 338winmag, Aug 1, 2011.

  1. 338winmag

    338winmag Well-Known Member

    Jan 9, 2011
    Good Day All,
    I was looking thru some posts a few weeks ago and saw where some well experienced and seasoned reloaders mentioned and\or agreed with the following:

    " ... seating distance is the single largest factor in accuracy .."

    It was also mentioned that once you find the sweet spot seating depth, making some adjustments with the powder charge would not affect the groups as significantly.

    I certainly do not have the years of experience that some have but .... among other things; seeing that the bullet touches the barrel as it travels downward... barrel harmonics are affected and are not static for each bullet or bullet type. In other words, different bullet velocities change the assocated barrel harmonics as well....

    Having said this, I decided to test the theory that powder throws are not "quite" as significant as seating depth. Wth 4 rifles and their applicable reload recipes that were in sub moa groups I went to the range and changed powder charges +- .2 and .3

    Groups immediately opened. No if ands or buts.

    I noticed a post on another forum. Increased the charge either .2 or .3. Groups went from almost 1.5" to sub moa.

    My experience tells me both are very important, critical and go hand in hand. Actually I might be able to make a .005 - .007 adjustment in seating depth and nothing happen, but if I make a .2 change in powder, it makes a difference.

    My conclusion; there is an associated correlation between sweet spot seating depth and sweet load powder charge. The combination can be fairly easily affected by changes to either, thus requiring to reload test all over again.

    Heck, maybe this is what you are all saying to begin with and I just didn't understand

    Thanks All
  2. boomtube

    boomtube Well-Known Member

    Oct 8, 2007
    I've found that we don't need to be within .0000001% of anything for a load to shoot well; both charging and seating have a 'window' in which small variations make little or no difference. Most charges may vary as much as .4-.8 gr. and seating may vary as much as 8-10 thou before most loads will be affected IF the load is properly chosen. Find the full range a load shoots well in and load in the middle of it, then small variations won't matter and otherwise 'unexplainable flyers' go away. But, if we load on the ragged edge of a window then small changes the wrong way WILL produce flyers.

    The most critical part to finding an accurate load seems to the be bullet itself. Some rifles just aren't accurate with anything, some simply don't like some bullets.