- February 10, 2016 at 1:16 am #23446
Some of you might remember my “consistency applied” thread in which I cast 300 bullets in a row of exactly the same weight?
Well, that was a great run, and I saved the bullets and have only shot a few of them. Tonight Sgt.Mike came by and asked me for some lead to cast 30XCB out of, and I reminded him that I had all those bullets still on the rack.
When I pulled them down, and dug him out a hundred or so, I found the hardness test bullet that I had cut in half and measured moments after casting, and again 1 week later.
I decided to test it again and compare the results, which I found interesting, and I thought you might also.
The first test I ran gave me 20 BHN 45 minutes after it was cast (Middle impression on the bullet below)
The second test gave 27BHN one week after it was cast (RH impression on the bullet below)
The third test gave 20 BHN on the same surface 1 year later (LH impression on the bullet below)
Finally, I pulled a fresh bullet from the same pile and filed down a ways and checked the fresh surface. The hardness was 27BHN.
Now I’m no expert, but it sure seems to me that the surface of the previous bullet got softer over the past 12 months.
- February 10, 2016 at 2:00 am #23453
- February 10, 2016 at 2:11 am #23455
I have tested at least 6 of these bullets by filing a flat on them and taking a reading. They always come in at 25-27BHN and I have shot them to 2700FPS. I am very sure of this measurement. I just wish I had cut about a dozen of them in half back a year ago so I could test the aged surface for softness.
Still, you can easily see the impression on the right in the first picture is noticeably smaller than the other two impressions and the only difference is that impression was only 1 week old.
What I could do is file off the surface of the old bullet and retest in the same spots? If they all come in hard, that would be interesting no?
- February 10, 2016 at 2:17 am #23458
I was just wondering if the variation was age related or changes more than I would think it would when tested at different locations on the same bullet. Either way, I agree, if it is age related or not….a very interesting observation.
- February 11, 2016 at 1:34 am #23551
I was curious, so tonight I took the original bullet with two soft impressions and one hard one and I filed down below the marks. Interesting that as I filed, I saw faint color changes under where the year old impressions were made. I kept filing till I had wiped out all trace of the original impressions, then I took three more in roughly the same locations.
All three new impressions measured 26-27 BHN.
These bullets have gotten softer on the surface over the course of 12 months. No doubt about it.
What keeps running through my mind is that certain clients who shoot HV have definitely shot better with bullets that were freshly cast, than with bullets that were several months old. I know there are people of questionable repute who claim bullets need to age three years to really get them to a point they are suitable for HV shooting, but this would seem to suggest otherwise.
Here is the picture of the original bullet with the three new impressions:
- February 11, 2016 at 5:20 am #23591
So looking at your results, I would agree it appears to be age related. However could this be an effect of the environment which the bullets were exposed during a one year or so period or what may be another interesting test to see the hardness level is better maintained if the bullets are PC’d (sealed from the environment) and stored.
- February 11, 2016 at 9:06 am #23593Wright ArmsParticipant
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Very interesting. Do you suppose the difference in hardness is due to oxidation? Was the sample bullet stored in a different condition than the remaining run? In a ziplock baggie or plastic bowl, perhaps? Have you tested any of the original run just on the surface, without creating a flat? Not the ideal test scenario, I know, but if the change occurs only on the outer layer, you might be removing by filing a flat? Just thinkin’ out loud . . .
- February 11, 2016 at 12:06 pm #23601
Wright Arms;n1648 wrote: Very interesting. Do you suppose the difference in hardness is due to oxidation? Was the sample bullet stored in a different condition than the remaining run? In a ziplock baggie or plastic bowl, perhaps? Have you tested any of the original run just on the surface, without creating a flat? Not the ideal test scenario, I know, but if the change occurs only on the outer layer, you might be removing by filing a flat? Just thinkin’ out loud . . .
The bullets were stored in my workshop, where the temperature and humidity varies throughout the year, and the sample was with them as I said in the OP.
I do suppose this was due to oxidation, but that’s just another theory.
As I said, I have tested numerous samples of these bullets throuout the year, and I am very confident of the hardness of 25-27BHN, but I always filed a flat because I had to to get a clean test surface, and you cannot test on anything but a relatively flat surface.
I was talking to bjornb about this last night, and the reason I filed a flat on the XCB bullets was because there was no flat surface due to the pointed nature of the XCB bullet in particular.
It occurs to me that this is easily tested by anyone who has bullets cast of hard metal with a flat point on them. They can simply:
1. Take a reading off the meplat and record
2. File the meplat off by about .050
3. Take another reading and record
4. Repeat about 10 times
5. Take an average of the before and after and compare the two to see if the surface is generaly HARDER, generally SOFTER, or generally THE SAME over time.
What say you?
- February 11, 2016 at 12:22 pm #23603MilkmanParticipant
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goodsteel, I guess I’m missing something. If the original bullet measured about 27 after a week, and a different bullet from the same bunch measures about 27 now, and the original bullet measures about 27 below the original tests then wouldn’t the only question be why there was a single soft spot in the original test bullet?
- February 11, 2016 at 12:33 pm #23604
Milkman;n1658 wrote: goodsteel, I guess I’m missing something. If the original bullet measured about 27 after a week, and a different bullet from the same bunch measures about 27 now, and the original bullet measures about 27 below the original tests then wouldn’t the only question be why there was a single soft spot in the original test bullet?
That is a real possibility. I wish I had more 1 year old sectioned bullets. I’m going to dig through my stash and see if I have anything with a flat point that was cast hard so I can explore this further.
- February 11, 2016 at 1:03 pm #23606
I found some bullets that were as old as the original bullets. I think they are cast of the same alloy and they have a flat point. However, they are only 25BHN and they were stored in a plastic baggie like nearly all my bullets are.
Taking measurements from the meplat, I could detect no difference (I only tested two due to time constraints).
I’m wondering if the original bullets might be compromised by having been exposed to the open air?
The other possibility is that like Milkman suggested, I just had a soft spot in the alloy.
More testing is required.
I think I’ll section a bunch of bullets and test them, record the results, then set them aside to age, both in the open air, and in a baggie, and retest in 6 months or so.
- February 11, 2016 at 7:14 pm #23640popperParticipant
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I just had a soft spot in the alloy – tin migration?
- February 11, 2016 at 8:44 pm #23646
Since I do not have more than one sample of this particular run of bullets, nothing can be ruled out. It is interesting though, and duly noted. Even if it’s a soft spot, that is very interesting.
I’ll watch for similar results.
- February 14, 2016 at 1:26 pm #23921Kevin SParticipant
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Tim was the alloy #2? I was going to ask if they were heat treated, but I remembered you took 1 test 20 minutes after casting.
- February 14, 2016 at 2:04 pm #23928
Alloy was House alloy (It’s always house alloy unless otherwise specified). figure #2 cut 50/50 with pure lead. IE: 95.6/2.4/2.4
These bullets were slightly frosted and were water quenched from the mold.
They measured 20BHN right away. One week later, they measured 27BHN. They have been tested for hardness periodically throughout the following year, and they always measure 27 BHN.
The one weirdness was when I tried to measure a bullet that I had already cut a flat surface on a year ago.
It could have been a soft spot but I doubt it.
What I think is more likely is that the bullets surface was compromised by being exposed to the open air. These are the only bullets that were not kept in my Zip lock baggies.
On that note, if oxygen is getting to the surface and causing it to be damaged, one solution would be to store the bullets in ammo cans which get a lit piece of paper thrown in before the lid is closed.
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