What is a .338 LM called when . . .

Discussion in 'Rifles, Bullets, Barrels & Ballistics' started by David P. Herne, Oct 10, 2003.

  1. David P. Herne

    David P. Herne Well-Known Member

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    Gentlemen,
    What is it called when you change the angle of the shoulder on the .338 Lapua Magnum to 35 or 40 degrees, keeping all other dimensions of the cartridge the same?

    Dave
     
  2. DANTEC

    DANTEC Well-Known Member

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    no to Improved a case , body of the case must be straightened ( less taper )tp increase case volume .
    Original 338 LM was with military use in aim so with a lot body taper for reliable feeding and extraction on battle field and during military operation on single shot or carful care rifle body taper can be much less

    good shooting

    DAN TEC
     

  3. ricciardelli

    ricciardelli Well-Known Member

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    How about:

    338 LM 35

    or

    338 LM 40
     
  4. David P. Herne

    David P. Herne Well-Known Member

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    Fellas,
    Thanks for the feedback. I know its a strange question, at least insofar as its phrased. But I asked it because I thought someone had already done this (i.e. kept the case length the same, but changed the case body's taper and increased the shoulder angle). I guess not. Wonder what the results would be (in terms of PSI, MV, brass life, throat erosion, etc.). Probably not as deplorable as with cartridges like the .338/416 Imp. or .338 Yogi!

    Dave
     
  5. Brent

    Brent Well-Known Member

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    Dave,

    I didn't know you also meant the diameter at the shoulder would be larger reducing the taper, just thought you were meaning a sharper shoulder. In that case, that's all I plan on doing with the 338 Lapua Imp I'm fixin to build, .570" at the shoulder, 40 degree angle, tighter neck and call it what you want... it's an improved 338 Lapua any way you look at it. That's what I'm going to call it, the 338 Lapua Imp 40 deg....

    Whane called his 30/338 LI 35 deg the 300 WAMBOMAG, there's the 30 WOLF, the 300 and 338 Yogi and a bunch more just a little different than each other. I think they're all pretty much the same full case length on the 30 and 338 Lapuas mentioned above.
     
  6. David P. Herne

    David P. Herne Well-Known Member

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    Brent,
    Damn, bro! You're just full of surprises. We must be on the same wavelength or something. And yes, .338 LM Improved is the only appropriate name for the subject cartridge. I assumed DANTEC was right in his comments, however. I didn't think the shoulder angle could be significantly increased without also changing the case body taper as well. But if you're planning on doing it, then more power to ya! I really love to get a dummy round from you when your dies come in, too. By the way, whose making your dies?

    As for the other .338 barn-burners, I've recoiled from them like I have with the Lazzeroni-class wildcats in almost every caliber. I suppose I'm pretty fickle in that respect. I mean, I like big, fast cartriges. But I'm also always saying to people: 'Let's be reasonable now!". It really revved me up, for example, when we went from driving caliber .338 250-gr projectiles to a MV of 2750 fps with the .338 WM case to driving that same projectile to a MV of 3000 fps with the .338 LM case. But when Lazzeroni then came forward to show that their case could drive the subject projectile to 3250 fps, I thought to myself: "I feel for the rifle out of which that son-of-a-bitch has to be shot"! But even more importantly, I've just always felt as though it was time for a man to look at a larger caliber cartridge once he started wanting to see, for example, a caliber .30 cartridge shoot a 180-gr projectile to a MV of > 3400 fps!

    Regards,
    Dave
     
  7. Brent

    Brent Well-Known Member

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    Dave,

    I push the shoulder back at the neck junction to create the 40 degree shoulder and a much longer neck on mine (.405" nk), Wayne is doing the same thing to his too. The body/shoulder juncture is at the same distance from the casehead as the original 338 Lapua is. They could be left like this and never blown out to a larger diameter at the top of the body if one really wanted to, but why not blow it out and take advantage of the large increase in case capacity the 338 Lapua offers because of its major body taper...

    Moving the original shoulder/neck juncture up into what is now the neck does require one to neck ream and turn them because the of the ring where the juncture was and extra thick brass below that. They really are nice and even when done with the K&M turner and Ken's reamer mandrel after formed in the die and blown out with COW (cream of wheat). Jim Carstensen at JLC Precision did the Newlon FL bushing and Wilson seater dies using my chamber reamer.

    95.0gr RL25 and the 178 A-Max showed MV that were from 3367-3404 fps in the first test with this bullet and powder.
    Pressure averaged right at 55,979 psi for the 9 shot group, which was 2.1" at 300 yards. The 9 shot group was fired in less than 3 minutes to see if chamber temp increase was affecting cartridges setting in the chamber before the shots, which it did not, at least it didn't with this big barrel.

    This is exactly what I'm looking for, a higher MV, at lower pressure where I've found most bullets do there best at. If they shoot very well at the higher pressures and MV that's just icing on the cake, I'm happy with the MV at the lower pressure and that is what I was after if I had to go there for accuracy.

    Now, to start serious load developement...

    I'm hoping the 338 LI will push a 250gr at 3200 and a 300gr at 3000 fps at under 60,000 psi. Barrel length will be important in reaching the goal.

    I haven't got any spare cases to make a dummy round for you at the moment, need to get more formed. I'll send you one after a bit when I get a few more of them done.

    Recoil was something I just had to learn to overcome to be able to shoot the bullet weights at the speeds I wanted to achieve, don't really think about it much any more, especially after working with the 400gr 416 bullets at 2700 fps with 115-118gr of powder in the 416wby at the bench for so damn long. These big 30's and 338's don't even hold a candle to the kind of recoil that 12 lb. rifle dishes out.

    I agree, how many bullets do well after going beyond 3300-3500 fps... But, is it the pressure that causes the groups to deteriorate by deforming the bullet or the imbalances within the bullet itself, the extra acceleration in the rifling creating problems with the core and jacket or a combination of things. Some bullets still do extremely well beyond those speeds. It's a very interesting area I'd like to learn more about for sure.
     
  8. ktg

    ktg Well-Known Member

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    Mine was built by Carolina Precision and it's called a 338 A.T.U.C. I have no clue what it stands for. Almost no taper & increased shoulder angle.

    [ 10-16-2003: Message edited by: ktg ]
     
  9. David P. Herne

    David P. Herne Well-Known Member

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    KTG,
    E-mail me a photo of that little bastard next to a standard .338 LM case for reference. I've gotta see this thing! Also, what kind of ballistic performance are you seeing?

    Dave
     
  10. ktg

    ktg Well-Known Member

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    Here they are next to a .308 Win.
    [​IMG]
    I don't know if it increased velocity a lot, but the loads that are compressed in the unimproved version (which makes them suck) fit just right in the improved.