Powder lot to lot variation

Discussion in 'Reloading' started by Gregg C, Mar 20, 2019.

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  1. Gregg C

    Gregg C Well-Known Member

    Nov 15, 2017
    How much do you back off your load when cracking open a new lot of powder ? 2 percent? 5? This just bit me for the first time.
  2. greatwhitehntr

    greatwhitehntr Well-Known Member

    Feb 1, 2013
    I normally back off 2 grains and work back up.
    I know what you mean.
  3. wildcat455

    wildcat455 Well-Known Member

    Sep 13, 2017
    Yep. 2 grains for me also. Most of my stuff is large case rifle, 30-06 and up. I only have a couple 308 win and lower case volumes. Those I back off a grain.
  4. MagnumManiac

    MagnumManiac Well-Known Member

    Feb 25, 2008
    I never back off, I just blend the old powder into the new one. I blend even if it’s from different lots with nary a problem.
    If it’s an 8lb jug, blending a pound or two and mixing it up has never had a detrimental effect on my loading, a tweak here or there is normal as the year goes by anyway.

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  5. brian b

    brian b Well-Known Member

    Aug 15, 2004
    Depends on the powder, if it is RL22 or RL25 I will back off 3 or 4 grains. they seem to have more lot to lot variation than any other powders. With a powder like H1000 I will shoot my normal load and tweak a bit from there.
    Pointman likes this.
  6. Greyfox

    Greyfox Well-Known Member

    Jan 21, 2008
    While I traditionally would also back off a couple of grains and would likely continue this practice with loads near max or compressed, in recent years I have found very good lot to lot consistency with the Hogdon Extreme powders, specifically H4350, H4831sc, Retumbo, and Varget. Rather then run a reduced load, I have checked new lots with a 200 yard, 5-10 shot ladder over a grain or two of my prior load. With my two most heavily used powders, three different lots of Retumbo, and 4 different lots of H4350, I have been within 10FPS With accuracy/precision within.25MOA of prior lots. I have not had as much luck with some if the other brands of powder, often finding it neccessary to make charge weight adjustments. Given this, I will make an effort to acquire enough of a powder of the same lot with my primary LRH and competition rifles but this has proven to be more difficult lately given the frequently encountered shortages.
    This is my powder( and, or bullet lot change) ladder check.and 200 yard group sample of two different lots of H4350. Bullets lot changes will additionally be tested for POI(BC) at max range use.
    544AB158-795D-4C22-9E1D-A2DE7B71AC4D.jpeg New lot ladder 0EA3F4A3-0B4B-4002-93B9-EF17A629337A.jpeg Prior Lot 0A9D6966-D7A2-4AEE-AC7F-8B4FC0B1307A.jpeg New lot
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  7. ShtrRdy

    ShtrRdy Well-Known Member

    Jan 14, 2012
    When changing to a new lot I'll use the same powder charge and make a few test rounds to measure velocity. If it's different than what I was getting with the previous lot I'll use Quickload to figure out what the powder charge should be to give me the same velocity.
    Dean2, PewPewPew and Tidus56 like this.
  8. Gregg C

    Gregg C Well-Known Member

    Nov 15, 2017
    Thanks. I guess 1.5 grains below max is close enough to max to back down. Load wasn't showing excess pressure with previous container so I didn't adjust load from new bottle. Apparently was enough difference to get into the red. Going from full length sizing to neck only couldn't cause pressure increase could it ? These two things are the only things I did differently, and I'm kinda stumped.
  9. PewPewPew

    PewPewPew New Member

    Jun 29, 2018
    I like this a lot. I may just start doing this myself.
  10. Jerry M

    Jerry M Well-Known Member

    Aug 20, 2006
    For 25 years a Buddy of mine backed off and tested every time he used a new bottle of powder. He did not on the last batch of H1000 and sheared off a lug on a pre-64 Model 70. Varget users several years ago also had problems with consistency between batches of powder, several grain differences. Better be safe than sorry. Stuff happens.

    Good luck

  11. g0rd0

    g0rd0 Well-Known Member

    Mar 9, 2012
    me I just stay at or near start, never a problem. My main worry is primers now they can really make a huge difference in preasure
  12. ar10ar15man

    ar10ar15man Well-Known Member

    Aug 22, 2018
    what we buy as retail has an allowable variance.
    if your prior load was near the top, and the new powder is
    Hotter but in "spec' you may have issues.
    there are ways to figure it out quickly.
    chrono some loads of each is a simple test...just not at the top.
    crkckr likes this.
  13. Edward Pagliassotti

    Edward Pagliassotti Member

    Mar 7, 2018
    Am I assuming your original load is at or near max recommended? If not, then there should not be any issues pressure wise. Am I correct in my thoughts?
  14. cape cove

    cape cove Well-Known Member

    Mar 17, 2016
    Back in the 80's I use to load H-450 in my 270 Wea mag. My max load with a 130 gr Hornady was 74 grs of powder. Came time that I had to run a new lot, so I backed off to 71 grs and worked up. When I got to 74 grs , my old max, vel and pressure was way low and accuracy was bad. I decided to continue working up. Only when I got to 78 grs did vel, pressure and accuracy return to the old levels. There was no danger because lucky for me I went from a fast lot to a much slower one, but I've often wondered what might have happened if it had been the other way around. Since then , depending on case size, I always back of at least 4 or 5 grs and work back up. It does not cost much to be safe, just a few primers, bullets and little powder. JME
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