Range Report Melting Polymer Tips?

[celtics10]

I looked to see if this had been covered in the forums and couldn’t find much, so please help me out if you can. The short version is my drops are spot on with a ballistic calculator to about 350 or so and then they take a massive dump and I’m wondering if it’s from my vmax tips melting. Now for the long version. Rifle is a 24” 5.56 ar with a heavy profile barrel and an SWFA 12x42. Load is factory fiocchi 50 gr vmax with a BC of 0.242 going ~3250fps. I generally shoot about 0.75 moa 5 shot groups at 100. About a month ago I wanted to reverify roughly 2 year old drop data. I verified my zero, shot two groups at 300 with my old drops, which matched perfectly, and moved on to 500. My old dope was 3.0 mils for 500, and I needed 3.4-3.5 (about 0.1 of that was from the DA change, 1700 zero vs -700 that day). At 570 it was even worse, I needed 0.6 more than my old dope of 3.9, even after accounting for the DA difference. The little bit I’ve been able to find online about melting ballistic tips is extremely varied, but the supporters said it only really shows up past 300 and with MVs over 3200 - both things I’m seeing. I thought/hoped it was a scope tracking problem, but then I shot a tall target test yesterday, just through 6 mils mind you, and it passed easily. Can anyone share their experiences with ballistic tips melting past 300 and how to account for it? My solution so far has been to use my original dope for 0-300 and then make a new curve from 300 on using the BC of 0.242 and play with the MV in that calculator until my 570 observed drop matches the calculator. I know it seems a little convoluted but I’m a math person and it’s the first idea I had. This is definitely a rough short term solution, I'm thinking the BC would tank if the tips actually melt. Also, the difference in drop is 6.0 old vs 7.2 new predicted at 700 yards, which seems crazy to me. I’m looking forward to any advice you all have on the possible melting bullets.

Thanks

 

[TheOE800]

Not sure about distances or speeds, but Hornady claims they AMAX lineup with the ELD lineup to solve the issue of the melting tip.

 

[SporterII]

I would not expect much from that bullet past 300.

 

[PS-G1_Sniper]

I've shot 6.5 Amax's at 3100fps and 3200fps to 1000, 1400 and 1500 for years without issue. I have ELD-M's now and still use up my old Amax's because they work well. They don't drop out of the sky for me.

 

[Lowlight]

The bullet tips did not Melt in the traditional sense of the word. They deformed and affected the BC by lowering it.

This happened closer to 600 - 800 yards where they noticed it. On Doppler, they saw the changes and addressed it, hence the ELD.

David Tubb when he was designing his 6XC bullets noticed the same thing when working with Sierra and scrapped the idea of using a polymer tip.

It's not something you would really notice, it's more like the drop would increase when the bullet tip flatted up a bit.

 

[celtics10]

Not sure about distances or speeds, but Hornady claims they AMAX lineup with the ELD lineup to solve the issue of the melting tip.

Do you know if Hornady ever published what they changed in the polymer chemistry to make it more heat resistant? Just out of curiosity.

I would not expect much from that bullet past 300.

The drops are increased, but it's surprisingly consistent at least to 500 or so, ~1 moa for five shots at that range.

I've shot 6.5 Amax's at 3100fps and 3200fps to 1000, 1400 and 1500 for years without issue. I have ELD-M's now and still use up my old Amax's because they work well. They don't drop out of the sky for me.

I don't know if the Amax is different than the vmax (made in same factory and just branded differently or actually different make up and manufacturers). That could maybe explain it.

The bullet tips did not Melt in the traditional sense of the word. They deformed and affected the BC by lowering it.

This happened closer to 600 - 800 yards where they noticed it. On Doppler, they saw the changes and addressed it, hence the ELD.

David Tubb when he was designing his 6XC bullets noticed the same thing when working with Sierra and scrapped the idea of using a polymer tip.

It's not something you would really notice, it's more like the drop would increase when the bullet tip flatted up a bit.

I figured something like that was happening, the bullet tip must be bearing the brunt of the air friction. Do you know if he ever said that the polymer tips deformed consistently/predictably or if there was a lot of variation? If it is consistent, I would happily keep shooting these and just find my own dope. I only ever shoot this gun out to ~700, past that I switch to my 6.5.

Thanks for the replies everyone.

 

[Rob01]

Hornady published a lot of data on what they found and that they fixed it. You can look here and read. https://www.hornady.com/heat-shield

AMAX and VMAX are different bullet construction but the tips were the same material.

 

[celtics10]

Hornady published a lot of data on what they found and that they fixed it. You can look here and read. https://www.hornady.com/heat-shield

AMAX and VMAX are different bullet construction but the tips were the same material.

That's exactly what I was looking for, thank you very much.

 

[SporterII]

Celtics, good to hear. I am working up a 52 SMK load right now for PD ,s in South Dakota.

 

[celtics10]

Celtics, good to hear. I am working up a 52 SMK load right now for PD ,s in South Dakota.

In winds under 10mph, I can generally manage a ~60% hit rate on pdogs with the vmax round at 350-400 yards. Past that, the wind really takes charge, but my wind calling abilities have gotten much better in the last year so we'll see how the annual trip to SD goes. I live in southern Wisconsin right now, and a windy day here is about 7mph, so I'm pretty spoiled. Last year in SD the winds got up to 15-17mph, which was a lot for a Wisconsin boy with a 223, but a good learning experience. I picked up a 6.5 creedmoor this year and have been shooting as much as I can, and I'm excited to break it out for the 500-800+ yard shots on the pdogs. Best of luck to you on your trip.

 

[damoncali]

You can find the details in their patent application. They're just using different kinds of plastics - there's no special sauce or magic going on.

Details here: https://patents.justia.com/patent/20160169645

 

[Rob01]

You can find the details in their patent application. They're just using different kinds of plastics - there's no special sauce or magic going on.

Who said there was any magic? Not magic just working a problem with a different material that solves the problem.

 

[damoncali]

I was responding to the question about what Hornady did to the polymer chemistry to make it more heat resistant. The answer is they used a different plastic. Its not a process, just a different material.

 

[celtics10]

You can find the details in their patent application. They're just using different kinds of plastics - there's no special sauce or magic going on.

Details here: https://patents.justia.com/patent/20160169645

Thanks for sharing the patent, I have an undergrad degree in physics so I find all this stuff pretty interesting.

 

[damoncali]

Thanks for sharing the patent, I have an undergrad degree in physics so I find all this stuff pretty interesting.

In a former life, I was an aerospace engineer, and we used a polysulfone very similar to what's in their patent to make specialized electronics boxes. It's a pretty amazing material. It's just regular plastic, but we were able to use it in an application that 99% of the time requires aluminum. It's also some solid engineering that Hornady figured out and fixed the problem at manufacturing scale. I'm impressed. I'm sort of surprised at how much Hornady has invested in things that, truth be told, most of their customers won't appreciate. There's something to be said for doing things right.

 

[deersniper]

Hornady published a lot of data on what they found and that they fixed it. You can look here and read. https://www.hornady.com/heat-shield

AMAX and VMAX are different bullet construction but the tips were the same material.

It didn't say anything on the link, have the amax/vmax lines been updated with the new polymer?

 

[Rob01]

It didn't say anything on the link, have the amax/vmax lines been updated with the new polymer?

No the AMAX bullet that have been kept are the same as they were but for their use the tip deforming isn't enough of an issue as they are lower BC bullets. Also like with the .308 168 AMAX they are kept as they are used for LE spec ammo and needed to be kept that way for contracts.

 

[celtics10]

It didn't say anything on the link, have the amax/vmax lines been updated with the new polymer?

With reference to the vmax bullets, the 50 gr bullet has a published BC of 0.232. These bullets shed velocity fast and you should probably use some kind of banded BC, but just using the 0.232 value, I have found this to be accurate to 300, but at 400 I am 0.2 mil lower than predicted, and at 600 0.6 lower. I tried to shoot them at 800 just for kicks, but it was pretty windy and I wasn't able to get any consistent hits (for reference, the 69 gr stuff I also shot at 800 needed a 4-5 mil wind hold that day). I hope to be able to try out the 50 gr stuff at 800 again, just for kicks if nothing else. Basically with the vmax, if you want to shoot past 450, make your own dope tables vs using a ballistic calculator (and nothing against ballistic calculators, I love me some JBM).

 

[Velocity Chad]

Obviously steel has a much higher melting point than plastic....thousands of degrees for steel vs. hundreds of degrees for plastic.

That having been said, I doubt if you could get a gun hot enough through just shooting to melt the polymers of which today's guns are made.

Of more concern would be the "slide wear" problem. Steel against steel, if properly lubricated will last many thousands of rounds. Steel against polymer.....who knows?

I would think that a proper design would be to have a steel insert in the slide, and a steel channel in the frame (or vice versa).

So how much of an effect do you think frame wear in handguns has on ballistic coefficient of the vmax bullets being discussed?

 

[Rob01]

Yeah he missed the mark some. Bullet discussion. Not handguns. LOL