Cooper arms 280 ackley velocity

Discussion in 'Reloading' started by goatliver, Dec 13, 2011.

  1. goatliver

    goatliver Member

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    Hello all
    Recently I have come up with a load giving me good accuracy.... 3/8-1/2 MOA out of my Cooper arms .280 AI excalibur. The barrel is 24 inches. Nosler advertises MAX 62.5 grains of H4831 giving 3179 FPS and Hodgdon shows MAX 62.0 grains of H4831 at 3012 FPS. My currently load is 62.1 grains of H4831, Nosler brass and F210 primers. My last range session I chronograph my load at a disappointing 2840 FPS........ not even close to 3000 FPS. Has anybody had a similar experience with H4831? I chose H4831 for temperature stability, however I am considering RL 22 for the extra speed. Any thoughts??
    Thanks
     
  2. Casing

    Casing Well-Known Member

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    Believe it or not you chose the right powder. What weight bullet are you shooting? I shoot 140 grain Nosler accubonds. I shoot 59 grains and then jump up to 62 grains. My best accuracy is with 59 grains and I get 3/8" groups at 100 yds. The group opens up a little as I increase the powder then tightens back up at 62 grains. I get almost 2900 fps at 59 grains and then 3100 plus at 62 grains. The velocity is less than RL 22 but the temp sensitivity was driving me crazy! I got tired of my point of impact moving from season to season with RL 22. I was getting over 3200 fps but the inconsistent groups were not worth the velocity. I love using H4831sc because I know where my bullet is going to go. I can do without 100 fps for the accuracy.
     

  3. TOM H

    TOM H Well-Known Member

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    I would chronograph the load again also the test barrel is a Wiseman 1/19 twist 26" long. We have one 280AI with 25" long Kreiger barrel using Nolser load for the 150gr with H-4831sc we get little better than max published velocity (3000fps) at 1gr under max.

    I had a factory Rem 280 with 24" long barrel I was going to use that action as donor for another 280AI want to have build. Alliant site has some loads for the 280 max 53gr/R-17 with 145 Speer @ 2968fps. I started at 50gr with 145gr Speer @ 2656fps max of 53gr @ 2904fps.

    You could have problems with the chronograph if you have another rifle that you shot over it before use that to check it with. If that check you might want to call Cooper see what they say before spend lot on more powder etc.

    Wish I could help more
     
  4. hypersonic

    hypersonic Well-Known Member

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    You have not mentioned bullet weight I use H- 4831 with 140 grain bullets in my 280 which is not the AI version and IMR-7828 with 160's. You have not mentioned if you are seeing any pressure signs with your current load so perhaps you could work up a bit to see if speed increases with your combo and then tweak for group size. I am getting 2820 with 160 Ab's over 7828 in my standard 280 but this rifle has a really fast barrel and I wish all my rifles were as easy to work up as this one has been. In the standard case for me Rl-22 was a wee bit faster than H-4831 but not even close to group size. Do not rule out RL-19 either if 4831 is not working for you I have had this powder turn a pig into a princess on a couple of ocasions right before I wrapped the rifle around a tree.

    Best of luck
     
  5. yawn

    yawn Well-Known Member

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    I'v had the same rifle/cal with a 23" barrel for a couple of years,for the 140-160gr bullets N560 gave best velocity,but like RL22 was a bit temp sensitive.I use N165 now as its better with the 160gr weights.As has been said do not trust your crony unless its an ohler or maybe a CED 2 with ir screens.With the shooting chronys Iv seen 100fps spreads with nothing more than a change in light conditions.The 140 gr TTSX I run at 3100 and 162 amax at 2920 av.both validated at range.
     
  6. Forrest Ebert

    Forrest Ebert Well-Known Member

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    I shoot the 280AI as well and have found a load of 63.5 grains of Retumbo with a Berger 168 grain Hunting VLD is right at 3,000 and 1 ragged hole. I have a 26" Pac-Nor barrel and a blue printed and squared Rem. 700 action in a HS precision stock. I have found this combo to be excellent in all weather conditions from 12-90+ degrees. There was a writer named Bob Milek that had some pretty hot loads for the 280Rem. as this was one of his favorite calibers . He has passed some years ago and I have lost the article he published these loads in but if you could find them they may be of help.
     
  7. goatliver

    goatliver Member

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    Thanks for you inputs guys. The bullet in question is a 140 gr Nosler AB. My chrono set up is a CED 2 Not the IR version. I am just surprised at 62 grains of H4831 i am not getting at least 3000 FPS. I will also switch back to the original Primer (WLR) which I haven't had the opportunity to chronograph.
    Regards
     
  8. TimeOnTarget

    TimeOnTarget Well-Known Member

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    That rifle is a lost cause!! Sell it to me cheap:D

    Sorry i have no useful info for you, i want a cooper in that same rifle.
     
  9. yawn

    yawn Well-Known Member

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    you won't de dissapointed :)
    [​IMG]
     
  10. goatliver

    goatliver Member

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    Hey TOT
    Its definitely one of my favorite rifles. Topped with a a Swaro Z5 and extra low talley quick detach........ its an awesome set up.
     
  11. TimeOnTarget

    TimeOnTarget Well-Known Member

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    Dang it you guys! Your gunna get me in big trouble with the wife!
     
  12. barreltwister

    barreltwister Active Member

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    Today we chronyed a 280AI that my son had built a few months ago. Didn't have time to play with it much before the hunting season.
    140 TTSX's run from 3312 to 3333 fps over at least 20 rounds. This with Rel22 in a 24" long 9" twist Shilen #2 barrel.
     
  13. goatliver

    goatliver Member

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    We're you close to max? Those are some good numbers!
     
  14. barreltwister

    barreltwister Active Member

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    This was 64.5 grs of Rel22 in a new Nosler 280AI case.