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

 
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Old 08-21-2014, 05:07 PM
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140 A-MAX fails in flight to target @ 2950 fps

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.
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Old 08-21-2014, 05:41 PM
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Re: 140 A-MAX fails in flight to target @ 2950 fps

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.
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Old 08-21-2014, 05:45 PM
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Re: 140 A-MAX fails in flight to target @ 2950 fps

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Originally Posted by bigngreen View Post
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.
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.
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Old 08-21-2014, 06:37 PM
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Re: 140 A-MAX fails in flight to target @ 2950 fps

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.
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Old 08-21-2014, 07:12 PM
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Re: 140 A-MAX fails in flight to target @ 2950 fps

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Originally Posted by IdahoCTD View Post
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.
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.
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Old 08-21-2014, 07:13 PM
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Re: 140 A-MAX fails in flight to target @ 2950 fps

Quote:
Originally Posted by bigngreen View Post
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.
Quote:
Originally Posted by Michael Courtney View Post
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.
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.
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Old 08-21-2014, 07:21 PM
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Re: 140 A-MAX fails in flight to target @ 2950 fps

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..
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