338 LM Improved w/ gain twist barrel

Discussion in 'Rifles, Bullets, Barrels & Ballistics' started by JeffVN, Jun 18, 2010.

  1. JeffVN

    JeffVN Well-Known Member

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    Some of this information is located on a bullet-testing related thread, but I thought it deserved its own thread to talk abou the load testing and gain twist barrel.

    My 338 Lapua Magnum Improved rifle was designed from the ground up to shoot some of Noel Carlson's ultra high BC lathe-turned, banded solid bullets out to and hopefully beyond 2,000 yards at my home desert range in Nevada, elevation 2,100 ft. The rifle has a 32" (not including break) Bartlein gain twist barrel (starts at a 12" twist at throat and exits the muzzle at roughly a 5.4").

    Here is a picture of a dummy round using blown out brass from the same reamer and one of the 338 7 caliber long ZA bullets seated to roughly proper length. The tip of the ZA has been flattened by my gunsmith to prevent injury. . . as when I shook it out of the box it hit my palm point first and drew blood...nasty and TRUE.

    Here she is on the left, next to the 7WSM and 284 Winchester (with 180 Berger's seated to their shooting length in my 7WSM and in my brother's .284 Winchester. On the left is a piece of new 338LM brass and a hydraulically blown-out case to my improved reamer design.

    The 338 total length is right at 4.135 inches
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    This is what the rifle looks like. Manners T2-A in Coyote Brown, Barnard PL 338 single-shot action, 32" Bartlein gain-twist barrel, March 6-60X scope w/ tactical ranging reticle, and a removable Badger FTE break....(for the AAC Titan Suppressor that is on order for it). The rounds shown with it are the 338 LM Improved with 7 Caliber ZA, my 7WSM with Berger 180, and a .308 with 170 Lapua Lockbase.

    [​IMG]

    Range Day-1 I ran the first 8 rounds through the rifle. The bullets were GS Custom 295 grain SP lathe turned solids. I was just trying to get a feel for the rifle and see if I could find the pressure limits with H. Retumbo powder (suggested to me by Greg Tannel). The Temp was a bit spicy, 92 degrees in the shade when I started and 96 when I stopped (as in from 7:45 am to 8:45 am).

    I loaded up 2 rounds with 95 grains, 2X 96, 1X 97, 1X 98, 1X 99, and 1X 100 grains of H. Retumbo. To my surprise, I never found a cratered primer or ejector mark on the brass; no pressure signs at all. So 100 grains is well within the pressure limits of this particular firearm; the 100 Grains was producing 2,980 fps. I wanted to push it a touch faster to see if 102 was near the pressure limit and what it mean in terms of velocity. My original goal was to get close to 2,950 fps for my accuracy load with the 300 grain bullets.

    Amazingly, the last 4 shots, 1X each at 97, 98, 99, and 100 grains, formed a nice little .75" outside edge to outside edge roughly 1/2 MOA clover-leaf group on the target. The slowest load (95 grains) produced a velocity of 2,840 fps; the highest (100 Grains) produced 2,980 fps.

    How confident am I in those velocity numbers - VERY. I recently picked up a second CED Millennium chronograph, and had them set up end-to-end so both could measure the same shot. They were producing different numbers for each shot (to be expected), but the velocity differential was consistent shot to shot. The numbers shown above are the average of the two chrono results.

    Range Day -2. This day was even hotter than Day 1. Temps ran from 96 to 102 in t he shade, so velocities were also higher. Again, no pressure signs at all. The loads with these bullets are running with low pressure and pretty uniform velocity (pretty tight ES and SD). I have gotten a uniform (only 3 shot groups so far) roughly 1/2 MOA groups at 100 yards, for ALL loads between 98.5 grains of Retumbo to 100 grains of Retumbo (1/2 grain increments). Every one of the 1/2 grain groups measured outside edge to outside edge .75" or slightly less.

    Sadly my load development has stopped for the short term until I can get more of the GS Custom 295 SP bullets. I only purchased 50 and that has not been enough to provide me with definitive load development results. I am satisfied that my 1/2 MOA results are solid, but there might be a better load out there and if so it would be nice to find it. At very long ranges I would prefer 1/4 MOA to 1/2 MOA any time. Granted, the shooter makes up for a ton more accuracy at the target then that, but it's a confidence thing to me. (I am holding by my last 18 bullets to shoot steel out to 1,800 yard with my brother and a friend from Houston.)

    I will post more from my Desert shooting trip and loading results with the rifle as they are known.
     
  2. Broz

    Broz Well-Known Member

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    Very interesting read. Thanks for posting. Look forward to more of yor testing with the gain twist.

    Jeff
     

  3. trueblue

    trueblue Well-Known Member

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    Jeff,
    Thanks for the post. I find reading about these solids made by Noel and others, GS, very interesting. Also, the linear and variable twist barrels are interesting as well. ELR is certainly cutting edge stuff, so good luck with your project. Keep the imfo coming.
    By the way, very nice looking rifle.
     
  4. JeffVN

    JeffVN Well-Known Member

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    Sorry if there has been any confusion. Yes the picture is of one of Noel's 7 caliber 338 projectiles that I have loaded as a dummy round. That was to show the round as compared with other chambering that I shoot and use.

    However, the load testing and velocity and accuracy data mentioned to date is all involving the .338 GS Custom 295 grain SP lathe turned banded bullets. Iwill post a picture of that round loaded and ready for action to resolve any of the confusion of what is going on.

    JeffVN
     
  5. japple

    japple Well-Known Member

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    Jeff,
    Sweet looking rig! Who built it? Why did you choose the gain twist barrel for it! does it shoot how you expected it to?
     
  6. kellyzier

    kellyzier Well-Known Member

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    I know this is an old thread,,,With all this time, what kind of results have you had with Noels bullets out to 1,000 yards with your 338??

    zman
     
  7. Broz

    Broz Well-Known Member

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    Actually it is only one day old.

    Jeff
     
  8. JeffVN

    JeffVN Well-Known Member

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    I do not have any results with Noel's bullets, as I have not received any to test. He has had family issues that have prevented him from making any bullets for a while.

    Because I had no ZA bullets to test, I decided to test the GCS Custom 295 Sps first - they were in my garage and ready to go.

    The Rifle was built by Alan and Dan Warner of Warner Tool.

    I chose the gain twist barrel specifically to shoot the ultra long, ultra high BC bullets from GS Custom and Noel Carelson.

    I strongly suspect that the 5.4 " exit twist is too high on this barrel for most jacketed bullets to survive.....but so far I have been unwilling to pull the break off of it and shoot a a jacketed bullet downrange to test that theory.

    JeffVN
     
  9. gunman123

    gunman123 Well-Known Member

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    Hi Jeff,

    How did your test go? Edit Oops...I saw you ran out of projectiles.

    Steve
     
    Last edited: Jun 22, 2010
  10. RockyMtnMT

    RockyMtnMT Official LRH Sponsor

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    I don't believe that the GS bullets need a gain twist barrel.

    I am anxious to hear your test results. Especially beyond the transonic range.

    Steve
     
  11. JeffVN

    JeffVN Well-Known Member

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    Me too. I ran into some issues on the rifle side. I am not sure exactly what is happening, so i didn't shoot to 1,760 with the 338 LM Improved. I didn't get to see the trace, but both my observers, both with military, and significant spotter scope and range time on their own, repoted the trace was "very odd."

    I will revisit the 90 yard target point at my home range and see if I can figure it out with the remaining few rounds that i have. If not it will be at least 3 months before I can get any more GS Customs to shoot.

    The day was not a total loss, as both Randy and I got to 1 beyond mile (1,780 yards) with my 7WSM, and my brother got there with his .284 Winchester, so I thought I would show off that picture, and a few of the site.

    [​IMG]

    One mile target. With Randy from Houston, Former Army Ranger and current NASA Mission COntrol rocket scientist. The light hits are from .284; darker hits from 7 WSM (14 hits total).

    [​IMG]

    Standing on the firing point (borther Jon, me, Randy); mile target is past the intermediate hill and just above right shoulder of person on far right.

    [​IMG]

    from the target, looking back to the firing point, past the intermediate hill, the firing point is between my thumb and index finger.
     
    Last edited: Jun 28, 2010
  12. Broz

    Broz Well-Known Member

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    Great pics and awesome shooting Jeff. Thanks for posting the follow up. Looks like a fun place to shoot. gun)gun)

    Jeff
     
  13. JeffVN

    JeffVN Well-Known Member

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    Well I received a PM from Gerard on another site regarding my possible bullet stability issues. Gerard does not believe the GS Custom .338 295 SPs will perform from the gain twist barrel on 338 LM Imporved, stating that the twist is far too fast, which is cause the bullets to not properly nose over. (That is my very rough paraphraseing of Gerard's email....so if I screwed up his statement blame me, not Gerard on his sdsicription of the problem).

    So I will be testing the ZA 338s fairly soon, and also the Predator 338s, to see how they react to teh gain twist barrel that I have on the 338 LM Improved.

    JeffVN
     
  14. JeffVN

    JeffVN Well-Known Member

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    I posted this on another site yesterday...

    After talking with Noel he agreed that I can release some information of the current status of my testing of his 6.5 Caliber ZA Bullets. I thought it was a good time as any to bring this particular thread back from the dead (since the rifle and projectile pictured here is what I tested again yesterday).

    I was testing 2 different versions of the ZA 6.5 caliber 338 projectiles (both are over 2" long One is 295 grains, and the other 276 grains) to see how they reacted in the denser air of the desert during winter.

    A touch of background - I tested the 6.5 Cal 295 grain bullets this summer in 90 degree heat and velocities up to 3,150 fps. They shot well for me at all speeds out to my local range's longest testing distance with a solid back drop to see bullet impact - 957 yards - and fully stabilized leaving crisp round holes in the target and plywood backer.

    Today I shot the same bullets with the same loads in 30 degree temps and 25% humidity. Although they were stable at slower speeds, they DID NOT stabilize at roughly 3,000 fps or anything faster then that. It was not a total surprise, as we expected that might be the result in the denser air at colder temps. It sort of goes with living on the ragged edge of stability with the 5.4" twist that I have on the current barrel.

    Interestingly enough, the ZA 276s, were fully stable at all speeds that I could produce yesterday, right up to high pressure onset and a primer leaking (my signal to stop at 105% compressed load with Retumbo). I will shoot them again to verify my velocity with the chronograph, but I am very confident that they were at 3,150+ if not a touch above 3,200 fps today. For those who are inquiring minds, I needed right at 15-6 MOA (MOA, not IPHY) to get from my verified 100 yard zero this morning to 957 yards.... I spotted a hole in the target at the bottom edge and am not sure when it showed up, so I want to be conservative in my BC estimates and holdover elevation.

    hmmm you tell me the BC of that little beast if my velocity prediction is even close to accurate @ 3,200 fps. Here is a hint... start with a 0.9_ _..

    I'll shoot them again , and report back with the velocities that I get on my chronograph. Fingers crossed, I might get some more at distance and some load development in tomorrow.

    It looks like the ZA 6.5 caliber .338 solid is darn near ready for its public unveiling.... nice.

    JeffVN