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

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  #29  
Unread 08-25-2014, 11:27 AM
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Re: 140 A-MAX fails in flight to target @ 2950 fps

Just a data point to add to the jacket heating data.
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  #30  
Unread 08-25-2014, 11:42 AM
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Re: 140 A-MAX fails in flight to target @ 2950 fps

Quote:
Originally Posted by jfseaman View Post
These posts go the same direction I was thinking about on a long drive.

I HBn coat my bullets. Lower friction.
It is interesting to note that Berger's study using the thin and thick jacketed bullets used coated bullets.

We've done some careful quantitative studies on the relationships between bullet coating and measured friction, and determined that coating bullets does not reliably reduce friction. See: www.dtic.mil/cgi-bin/GetTRDoc?AD=ADA568594

This study found that in some cases, bullet coating actually increased the friction.

I would regard whether or not bullet coating reliably reduces jacket heating as an open question. Even if it does not reduce friction, it may reduce heat transfer to the jacket if more of the friction generated heat ends up in the barrel or coating material.
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  #31  
Unread 11-02-2015, 06:36 AM
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Re: 140 A-MAX fails in flight to target @ 2950 fps

Quote:
Originally Posted by varmintH8R View Post
I am pretty sure (but not positive) the tips on the A-Max are made of Acetal. Acetal has a melt point of about 335F. It is also a semi-crystalline plastic, meaning it will begin to lose stiffness well below that melt point (roughly 220F heat-deflection under moderate load). Your hypothesis about the tips contributing to the failures may have merit - also consider that the metals surrounding these tips are picking up and conducting heat as the day goes on (ambient temps rising, barrel temps rising). This is effectively "pre-heating" the tips over time.

As stated in earlier posts, starting at a higher temp (even just 15 or 20 degrees) can make a huge difference in getting a material into "the red zone". Flight time of that bullet is pretty short, so the heat created by friction "soaking in" to the part has to happen quickly. Starting with a "pre-heated" tip will make a dramatic difference. Heat resistance of plastics is a function of both temperature and time (and how much mass there is to heat up).

The melt temp of lead (according to Wikipedia, I'm not a metals guy) is stated to be 621F.... I would expect an Acetal tip failure way in advance of melted lead.

Pure conjecture as to whether it contributes to the the actual failure method, but rooted in materials science


Brandon


Hey, looks like my hypothesis was validated! Even a blind squirrel!


Hornady’s New ELD-X Bullets
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  #32  
Unread 11-02-2015, 12:08 PM
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Re: 140 A-MAX fails in flight to target @ 2950 fps

so is this some crap cooked up to showcase how awsome the new ELD is supposed to be?

cause it sure seems like it to me
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  #33  
Unread 11-02-2015, 12:32 PM
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Re: 140 A-MAX fails in flight to target @ 2950 fps

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Originally Posted by Radhimself View Post
so is this some crap cooked up to showcase how awsome the new ELD is supposed to be?

cause it sure seems like it to me
Check out the date on the first post 8-21-14. This is an old thread that was pulled up as fodder for conversation on the new ELD.
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  #34  
Unread 11-03-2015, 11:33 PM
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Re: 140 A-MAX fails in flight to target @ 2950 fps

I don't have anything in 6.5 , but I do shoot .224 Diameter 80 gr. A-Max bullets from a .220 Swift , with a 1: 8" twist barrel , at an average velocity of 3305 FPS , here in Texas @ 650' above sea level , in the heat of summer , 100 degree temperature days . I will usually fire from 50 to 100 rounds in a 2 hour period . I have never had an A-Max fail , and the count is over 1300 rounds .
Very accurate out to 1200 yards , so far .

Just my opinion , I am very pleased with the A-Max .
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