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loading data changes

castingcasting Member Posts: 116 ✭✭
edited November 2019 in Ask the Experts
I've been loading from Sierra's 4th edition manual. For 308Win it listed an accuracy load of 46.1 gr of IMR4064 for 150 gr bullets. That's what I loaded for years and it worked great for the most part. Recently I noticed they seemed a bit harsh. And not as accurate. Well the Sierra 5th edition puts 46.1 gr beyond their red line which is 45.5 for IMR4064. I like to keep the velocity around 2800fps. Am I correct to think a variance in powder formulation required this change. What I want to do is pull the ammo I have apart and recharge it. My question is, would a sensible person do this. I think I might have 40-60 rounds to do.


  • MIKE WISKEYMIKE WISKEY Member, Moderator Posts: 9,748 ******
    edited November -1
    " Am I correct to think a variance in powder formulation required this change. ".....................more like a change in law firms.
  • navc130navc130 Member Posts: 1,014 ✭✭✭
    edited November -1
    As I understand it, besides a change in the powder formulation, which is usually announced by the company, the improvement of the pressure measuring devices is much more sophisticated than the older ones. When the newer device shows a change in pressure of a published load the data is changed in the next edition of the reloading manual. This was particularly true of some loads published in the 50's and 60's that were found to be higher pressure than published.
  • castingcasting Member Posts: 116 ✭✭
    edited November -1
    Believe me I did consider the liability angle. After I posted this question I went to the Hodgdon/IMR website. 46.1 of 4064 is within their specs so I feel OK that way. I'll probably bust out my chrono and see what I get. If I'm close to 3000 fps I'll definitely pull what I've got loaded. I like to keep it around 2800. At some point I ran out of 4064 and opened a new one. And at some point I noticed accuracy falling off and more recoil.
  • TRAP55TRAP55 Member Posts: 8,277 ✭✭✭
    edited November -1
    Sierra updates their loading manuals because the 4064 of 20yrs ago, is not the same as the one made today. There are even slight variances between lots, and that's why attorneys keep an eye on their data. Hodgdon adds to the confusion using the same numbers on their powders as IMR powders, they may be close in burn rate, but are not the same.
  • pip5255pip5255 Member Posts: 1,614 ✭✭✭
    edited November -1
    I would not pull them I would use them as loaded then load new ones to new specs
    just because you could doesn't mean you should
  • AmbroseAmbrose Member Posts: 2,996 ✭✭✭
    edited November -1
    FWIW: I have been using IMR4064 with 150 gr. Sierra spt bullets as a "standard load" in my .30/06's for probably 50+ years. Earlier this year, I bought 2 sealed 1 lb. cans from a guy I trust (I couldn't pass it up for $25!). The date code on the cans indicated 2008 manufacture. Since I was working up loads for a new-to-me rifle anyway, I thought I'd experiment. I had a 2019 date code can on the shelf so I loaded 10 rounds with each powder. The 2008 powder averaged 2969 FPS with the 2-5 shot groups averaging 2.16". The 2019 powder, 2912 FPS & 2.56". As I said; FWIW.
  • MobuckMobuck Member Posts: 12,958 ✭✭✭✭
    edited November -1
    When changing powder production "lots", you should start over if your loads are above middle of the pack data wise.
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