338 Norma or 338 Norma Ackley?

Discussion in 'Big Stuff -- 6.5mm, 7mm, 30 Cal' started by TikkaSporter, Feb 13, 2018.

  1. TikkaSporter

    TikkaSporter Silver $$ Contributor

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    Seriously considering re-barreling my burnt out 338 Lapua to either a 338 Norma magnum or a 338 Norma Improved. I prefer to magazine feed with this rifle and after fighting donuts with the current 338 lapua chambering, going to something where I conceivably wouldn't have to seat the heavies into the neck-shoulder junction sounds like the best way to go. Is this realistic with the 300gr Hybrids and the 285 ELD-M's? My max magazine internal length is 3.750"

    Don't expect to gain performance over the 338 Lapua with the 338 Norma Improved, but hoping to maintain similar velocities without pushing too hard. Is that a realistic expectation? Also hoping to minimize case growth & trimming with the improved version. Obviously this complicates die acquisition, thinking custom dies, probably from Whidden...

    Is it worth it going to 338 Norma Ackley?
     
  2. Bart B.

    Bart B.

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    Ackley versions of cartridges usually get up to 25% less barrel life. With their heavier recoil, they're harder to shoot as accurate.

    I've no idea where this decades-old mythical standard for bullet seating that puts the bullet heel even with the case neck-shoulder juncture came from. Probably the same person who touched a slot machine display's four corners and center in the same pattern every time to increase their odds of jackpotting thousands.

    Seat bullets just deep enough to allow reliable loading from the magazine and easy ejecting.
     
  3. TikkaSporter

    TikkaSporter Silver $$ Contributor

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    Debatable, in general... In my case, going from 338 Lapua to 338 Norma Ackley, most likely going to be longer barrel life and similar recoil verses 338 Lapua. With regards, to the 338 Norma verses the 338 Norma Ackley, there's not a huge gain in case capacity because the 338 Norma case does not have a lot of taper to remove with the Ackley version.


    It's not mythical to me, having dealt with donuts and the associated pressure spikes, accuracy issues, inside reaming, throwing out expensive brass after only 5-firings, etc. There is no way to run a 338 Lapua at magazine length with 285 gr+ bullet weights and not seat the bearing surface of the bullet through the neck-shoulder junction (where donuts happen). The only sure way i know to avoid donut problems is to choose a cartridge/reamer/bullet combination that NEVER requires seating into/past the donut. If there's a better way, please enlighten me.

    The question I have: Is going to the 338 Norma Ackley worth the hassle (custom dies, fire forming, probably buying the reamer) verses just going to a straight 338 Norma and dealing with the 20* shoulder, more brass growth, losing 50 - 100 fps verses my previous 338 Lapua?
     
    oldroper and dragman like this.
  4. boltfluter

    boltfluter Gold $$ Contributor

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    Personally I would go improved. I have a friend that has one and it's a shooter. Little less bolt thrust, less trimming, and he shoots the 300 gr at mag length. Feeds fine. Now that Lapua is making brass this is a win win in my book. Whidden dies are well worth the investment. Great choice on your part. Have fun.:D:D

    Paul
     
  5. Bart B.

    Bart B.

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    Then you agree with me. At least that's how I interpret your comment.

    There are too many bad things that happen when the bullet heel is at or behind the neck-shoulder juncture.
     
  6. Drop Port

    Drop Port

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    Depending on your Lapua OAL you might be surprised at how little difference there often is between the 338 Norma and Lapua. If you give your old data OAL and FPS and Barrel length I could give you my 2 cents after having run several Norma's and about ready to re barrel another.
     
  7. fredo

    fredo Silver $$ Contributor

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    Given the magazine length constraint, a 338Norma AI makes good sense...

    Same logic for doing a 243AI over a (longer) 6mm Rem, from a short action. That being, the shorter case allows for a heavy (long) to be seated further out, thereby increasing useable case capacity AND negating any 'donut' interference issues...

    Where as, in order to stay < OAL magazine limitations, the longer case needs the same bullet seated, deeper. Which, in turn, puts the bullet in contact with a potential 'donut', and occupies case volume that would otherwise be used for powder...

    Given an OAL constraint to insure magazine feeding, It's not hard to see how a 'smaller' case can hang with a larger one.

    Naturally that argument is moot, if both cases are run at their 'ideal' OAL. In that regard, the bigger case always wins, by default of more 'boiler room'...

    Beyond that, sounds like it'd be a cool project! Have fun!!!
     
  8. TikkaSporter

    TikkaSporter Silver $$ Contributor

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    Yes, I guess I do agree with you then. I thought you meant it was a mythical standard that the bullet needed to be seated in-front of the N-S junction.

    I will say that if I start with the bearing surface right at the N-S junction with a freshly cut chamber and new brass, most likely by the time a donut has had a chance to form, the throat will have eroded enough to seat the bullet ahead of it... This is just my thought process in looking at reamer prints and measuring my current bullets from the start of the boat tail to the tips and trying to figure out how much room for throat erosion there is to work with, given my magazine C.O.A.L.:

    SAKO M995 TRG-s Internal Magazine Length: 3.760” = use 3.750” max COAL
    • 300 gr Berger Hybrid boat tail Bearing Surface-to-tip measurement: 1.557”
      • Ackley Reamer = 2.1449” boltface to N/S junction
      • 338 Norma Reamer = 2.1489” boltface to N/S junction
      • ~3.702” - 3.706” COAL seated above the N/S junction
      • Approximately 0.045” to work with for throat erosion
     
  9. TikkaSporter

    TikkaSporter Silver $$ Contributor

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    I'll have to look up my exact load data when I get home from the weekend... Off-the-cuff:

    - 27" Bartlein barrel. 1:10 twist. 5R rifling.
    - 300gr Berger Hybrid, Lapua brand brass, 91.5gr H1000, 2860 fps, can't remember OAL
    - 285gr Hornady ELD-M, RWS brand brass, 91.0gr H1000? (need to verify), 2875 fps, can't remember OAL
     
  10. Sniper338

    Sniper338 Silver $$ Contributor

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    You may want to check ouy doing a 300 Norma or 300 Norma AI... New heavy bulleys are coming out.. More Velocity, and ballistics are the same to slightly better than a 338 lapua.
     
  11. TikkaSporter

    TikkaSporter Silver $$ Contributor

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    and a shorter barrel life... I already have some cool-aid in the 30-cal flavor, but you are correct new bullets are changing the game.
     

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