140 A-MAX fails in flight to target @ 2950 fps

Discussion in 'Rifles, Bullets, Barrels & Ballistics' started by Michael Courtney, Aug 21, 2014.

  1. Michael Courtney

    Michael Courtney Silver Member

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    140 A-MAX fails in flight to target @ 2950 fps

    At an F-Class match last weekend in Donaldsonville, LA, my daughter had four of her last 20 shots fail in flight about 50 yards after firing. She was shooting 140 grain A-MAX bullets at 2950 fps from a 6.5-284 with a custom Lilja barrel with 1 in 8" twist.

    The bullet failures were obvious from the lack of hole in the target and the easily visible puff of smoke about 50 yards down range from the firing point. The bullet appeared to vaporize in flight.

    The load was originally developed in Colorado and provided fine service there for several hundred rounds without a problem. The Colorado ranges have much lower ambient pressure than Louisiana, about 30% lower than sea level pressures. We first started to notice a problem last summer after moving to Louisiana when one or two shots were occasionally lost during the last 20 shots of an F-Class match when all the other shots were 9s or 10s on a 600 yard F-Class target. However, in that case, no one was watching the bullet trail to see what may have happened in flight. After the fist shot was lost in Donaldsonville last week, two experienced spotters begin watching closely and easily detected the bullet failures in flight.

    It was a hot day (95 deg F) by the time the bullets failed, but since H1000 is a reasonably temp-stable powder, I would surmise that any heat related effect was most likely due to the bullet rather than the powder. An additional point of interest is that my wife and daughter have both shot the 139 grain Lapua Scenar from the same rifle without any problem in recent weeks. One gentleman at the match noted that he has also had problems with A-MAX bullets failing in flight at the Donaldsonville range, and he thinks it may be related to the plastic tip.

    The question of whether plastic bullet tips can melt in flight has been raised before, but without definitive answer. The conditions were certainly optimal in this case: hot day to raise the starting temperature of the bullet tips combined with (possibly) slightly elevated muzzle velocities, and high ambient pressure which would maximize drag (thus heating) of the tip. The hypothesis of spin-induced bullet failure seems less likely because all the failures occurred in the last match of the day.

    Since the bullet failures occurred, we have come across several threads discussing Eric Stecker's investigations and Berger's remedies of similar problems by making jackets thicker in their match bullets. In that case, it seems clear that the problem was related to jacket thinness and melting the lead with bore friction and heat transfer.

    We have written to Hornady describing these events. They have apologized and sent my daughter a ball cap rather than replacing the bullets to make up for her inconvenience. My daughter has moved on to 139 Lapuas and requested the cap instead of replacement bullets.
     
  2. bigngreen

    bigngreen Well-Known Member

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    Was it a Lilja 3 groove? I've seen several 6.5's start destroying bullets, all three grooves, some due to rough throat and some due to fouling getting out of control which can be related to ambient humidity and carbon fowling.
     

  3. Michael Courtney

    Michael Courtney Silver Member

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    6 groove. The humidity was high, but this barrel doesn't foul much. Only 700 rounds down the tube so the throat is still in pretty good shape. H1000 is a pretty clean powder. This is one of the smoother bores we've owned. Very quick clean up compared with most other barrels.
     
  4. IdahoCTD

    IdahoCTD Well-Known Member

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    I shoot the same bullet 3230fps out of my 6.5-300wm and haven't had a failure yet. My barrel has about 300-320 rounds through i and I shoot it quite often in 80+ degree temps. In the last couple years I've kill a couple elk under 150yds, a antelope at 513yds, and a deer at 1006yds with the same set up. It very well could have been the batch of bullets your daughter was using.
     
  5. Michael Courtney

    Michael Courtney Silver Member

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    Could be. But most people forget that air drag and resulting heating of the tip is proportional to the air density. Elevations with elk and antelope have much lower air density than south Louisiana which is very close to sea level. The aerodynamic forces on the bullet at 2950 at sea level can be greater than at 3230 at 5000 ft. Twist rate and tip off angle come into play also, since failure occurs before much damping of the pitch and yaw.

    This same lot of bullets never created a problem for us on the great plains or mountains at temps in the 80s, but started to cause trouble in Louisiana at temps in the 90s.

    There's no doubt that these bullets work fine in a lot of different barrels, or Hornady would be so flooded with complaints they would have fixed the problem. Figuring out why these bullets fail in conditions where failure is common is the more challenging task.
     
  6. FEENIX

    FEENIX Well-Known Member

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    I have a 3-groove 1:8 twist Lilja in my .270 AI and I too don't have any fouling problem using H1000, H4831SC, H4350, IMR7828SSC, and Retumbo thus far.
     
  7. Barrelnut

    Barrelnut Well-Known Member

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    I would lean towards the jacket thickness being the issue in a hot rifle on a hot day. I have been shooting some F-Class type stuff this summer and a barrel can start getting pretty warm during the last 10 rounds. I have also noticed that A-Max jackets seem thin on the ones I have recovered.

    I was using Bergers during the matches, but have shot lots of A-Maxes and have never had one blow up. Well at the blistering speed of 2750 anyway..
     
  8. IdahoCTD

    IdahoCTD Well-Known Member

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    Most of my hot shooting is done around 2600' elevation. Shooting elk and other animals is usually much cooler and higher elevation.

    My barrel is a 8 twist Bartlein 5R Sendero contour. A lot of times I run 3-5 rounds in under a minute through my gun when I'm shooting long distance. I know F-class involves more rounds but my barrel will get pretty hot fast too.
     
  9. bigngreen

    bigngreen Well-Known Member

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    Did you bore scope it?
     
  10. jfseaman

    jfseaman Well-Known Member

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    I've gone that fast at sea level 60% plus humidity, 70 degrees. Barrel temps at 140 degrees (temperature stickers).

    Bad batch?
    Sharp lands?
    Muzzle burr?
     
  11. Mikecr

    Mikecr Well-Known Member

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    My thinking is bad lot of bullets.
    There is no way to expect an integrity issue at such a lethargic speed, pushed gently with H1000, and normal twist.
    I wonder if a Juenke ICC would identify it..
     
  12. Michael Courtney

    Michael Courtney Silver Member

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    Bullet failure from a match barrel in good shape is an integrity issue, since the bullet was used within the design parameters.

    The only question is whether the integrity issue was a failure of this lot to meet the design or an inherent flaw in the design.
     
  13. jfseaman

    jfseaman Well-Known Member

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    If you have any left from that lot send em to Hornaday with a description. Don't complain just describe.

    They will do the right thing.

    IMHO: If you take an attitude of trying to help the will be very very nice but if you complain or focus on how you were wronged or harmed the will treat you like you are trying to harm them or retaliate.
     
  14. Michael Courtney

    Michael Courtney Silver Member

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    The matter has been forwarded to Hornady Engineering in a professional and friendly manner. We intend to cooperate with any ensuing requests for additional information or materials, but there have not been any yet.