need some help with 338 LM

Discussion in 'Rifles, Bullets, Barrels & Ballistics' started by revturbo9967, Aug 27, 2015.

  1. revturbo9967

    revturbo9967 Well-Known Member

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    I'm very new at reloading so bare with me. I've been trying to build up a good load for my 338 lm. Its a 26 inch barrel 1-9.3 twist. I've been shooting it at 100 yards trying to develop an accurate load and have come up with nothing be horrible groups. 3+ inches. It has been extremely erratic. I've stretched it to 200-300-and last night 400 yards. with the same results.

    Initially thought it was the bullets. I was using 300gr accubonds and just figured the gun didn't like them. Using lapua brass I started .020 off the lands and 90 gr of retumbo. Then worked my way up to 92 gr and just felt like something wasn't right with the bullet. Again, I'm new at reloading so I was like "whats a few more grains of powder going to do"? So I switched to bergers 300gr EH. I started all over and began at 89 then 90gr with the same horrible groups. Well last night, going after some 10 inch steel at 400 yards, I was able to hit it but at 2.6 mils high. Using noslers load data I thought I should be around 2600 fps which should get me around 1.9 mils at 400 yards. Only guessing, I'm actually around 2300 or less. What could be the cause for this low velocity? Could this also married with my crappy groups? I have a feeling its all tied together but i don't know where to go next.
     
  2. revturbo9967

    revturbo9967 Well-Known Member

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    anyone?
     
  3. screech

    screech Well-Known Member

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    I'd pick the bullets you want to use and seat them to where you want to run them first. In other words if you want them to fit in the magazine make them fit to that length. I'd run the powder you want to use. If it was me I'd try h1000 but you can try retumbo. Start at a mid load on the reloading manual then work up until you get pressure signs. I generally just run 3 shot groups To get something close.you should see your groups open up and close if your gun likes the powder. Generally this only takes 5-8 groups. With the size of case just use 1 grain increments. If it doesn't come up with something decent try a different powder and start the same process. If you don't find something within say 4-5 powders switch to your second bullet of choice and try again. After you find a bullet powder combo your gun seems to like then you can do additional tweeking if you like but generally this will get you a working load. If you need help pm me
     
  4. revturbo9967

    revturbo9967 Well-Known Member

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    i did that for the most part. im just confused why my velocity is so low compared to the book.
     
  5. shortgrass

    shortgrass Well-Known Member

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    Is this a custom build, or a 'factory' offering?
     
  6. revturbo9967

    revturbo9967 Well-Known Member

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    This is a factory rifle
     
  7. screech

    screech Well-Known Member

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    WhaT kinda chronograph are you using if you hitting 2.6 high sounds like you may have the wrong velocity for your software. I know I used to have a shooting chrony and finally bought an ohler35p because the cheaper ones were doing me no good because they didn't work well enough for precision work.
     
  8. revturbo9967

    revturbo9967 Well-Known Member

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    im not using one. i dont have one yet. im just going off of a few load data books info as far as the ball park velocity. it just seems way slower then what ive read
     
  9. el matador

    el matador Well-Known Member

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    Something is up with your gun if it's shooting that poorly. Could be a number of things, but erratic groups could be caused by:

    Fouled barrel (happens after 10 to 100+ rounds depending on barrel)
    Action screws not tight
    Scope mount or rings not tight
    Scope broken
    Inconsistent or unstable shooting rest
     
  10. revturbo9967

    revturbo9967 Well-Known Member

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    Everything with the scope is tight and good . The barrel on the other hand, I'm not sure. This is a weatherby accumark rife with 26 inch barrel. They have been nothing but tac drivers until I got this one.

    ive only got 158 shots through it and have scrubbed it 3 times since new. i thought i was having a dirty barrel problem but its just as erratic after a clean barrel
     
    Last edited: Sep 1, 2015
  11. el matador

    el matador Well-Known Member

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    Have you bedded your Accumark? That could make a huge difference. They are easy to do since they have the bedding block in the stock. I would also replace the trigger spring if you have not yet done so.

    I have noticed with my harder recoiling guns that rest positioning is very important. The gun needs to be able to travel freely and consistently as it recoils or it will throw your groups off. Rest the fore grip in the same place each time and ensure adequate clearance for the knob of the pistol grip. Even a swivel stud hitting somewhere can wreck your groups.

    Good luck man, these are awesome guns once you get them figured out.
     
  12. revturbo9967

    revturbo9967 Well-Known Member

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    i havent bedded the gun yet. but it sounds like i should. i replaced the accumark trigger with a timney . love it. as far as a rest I'm using a harris bipod
     
  13. el matador

    el matador Well-Known Member

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    Yeah I'd bed it for sure. I've read numerous tales of Accumarks that tightened right up after a bedding job. I think that the bigger calibers especially can have the action jumping around in the stock quite a bit.

    When I started shooting some of the harder recoiling guns I was getting quite a few inexplicably large groups. Even with loads that had shot well previously, I would get fliers, stringing, or just giant groups. Then I discovered that much of it was due to my shooting technique. Here is a great video about bipod shooting. When I started focusing on the mechanics explained here my shooting became a lot more predictable/consistent. It's a good refresher even for experienced shooters:

    https://www.youtube.com/watch?v=4cg0KxIzgS4
     
  14. revturbo9967

    revturbo9967 Well-Known Member

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    Thank you for your help. I'm glad I have something to look into other then just loads. The rifle seems awfully funny