This is the penetration without the AP and ballistic cap weight.
Close enough. You will never be able to get a perfect match, as every lot of the same ammunition and same armour plate will differ slightly and get you different results. If you estimate is within ±5% from average value from historic sources, consider it a success.
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Yeah, if we could estimate penetrator weights only, the formula would be more accurate.
Here’s the M62.
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I haven’t found an easy way to do it yet. What I showed you was not even the alpha version, it was a “proof of concept” where I mostly manually adjusted the coefficients of a parabola until it became flat where it crosses the y-axis and tangent to the curve of the penetration.
I hope one day to be able to simply adjust this one variable I called “quality factor” and have the computer do the hard work for me.
Do you have any estimates for the penetrator weight of the M82?
As a matter of fact I do. :)
The 90mm M82 to under represented. It comes out to 158mm at 853 m/s. The M82 has a lower caliber density and a larger filler charge to weight ratio than the M62.
This is why a deliberate curbing of the performance of uncapped AP is needed. Otherwise we would get situations in the game where the top shell that you unlock will be worse in 90% of cases to your stock one:
| Distance (m): | 2600fps 0° 2-pr. APCBC | 2800fps 0° 2-pr. AP ideal | 2800fps 0° 2-pr. AP nerfed |
|---|---|---|---|
| 10 | 81 | 93 | 70 |
| 100 | 79 | 87 | 69 |
| 500 | 69 | 67 | 63 |
| 1000 | 57 | 47 | 47 |
| 1500 | 47 | 33 | 33 |
Edit: real life data:
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That’s often the case already with APCR coming after APHE.
But (ideally) it shouldn’t be.
I agree, and I also agree that we should use historical data for penetration but Gaijin doesn’t want to do that anymore, so this is the next best thing.
so this is the next best thing.
See, this is were I disagree with you: I believe that a penetration calculator is not the “next best thing”, but the best thing, period.
Using raw historical data is a bad idea, because every test was performed under slightly different circumstances and the results never perfectly match with one another.
I’ve seen what happens, people just push to adopt the source that gives the best values for their favourite nation as the word of God and displays hostility whenever this notion is challenged.
A well calibrated mathematical model that works on the same laws of physics for everyone is the only objective arbiter of truth that can exist in such situation.
Of course, it needs to closely match the values that historical documents show, otherwise whatever positive qualities it might have, it will work poorly (see Gaijin’s implementation).
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I meant the next best thing is refining the calculator. The issue is how far do we take the refinement and how far is Gaijin willing to go.
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+1! Could be better? So make it better!
Oh, yes, it all comes together.
I found this 2pdr ballistic test data:
Long story short: after adjusting it appropriately to the scale of a normal 2pdr shell and interpolating the results, we get this table:
| 2pdr AP at 0° vs 260 BHN RHA | ||
|---|---|---|
| T(mm): | BL AP (fps): | BL APCBC (fps): |
| 20 | 1141 | 1163 |
| 25 | 1251 | 1276 |
| 30 | 1362 | 1389 |
| 35 | 1473 | 1502 |
| 40 | 1584 | 1615 |
| 45 | 1695 | 1728 |
| 50 | 1805 | 1841 |
| 55 | 1916 | 1954 |
| 60 | 2027 | 2067 |
| 65 | 2138 | 2180 |
| 70 | 2248 | 2293 |
| 75 | 2359 | 2406 |
| 80 | 2470 | 2519 |
| 85 | 2581 | 2632 |
| 90 | 2692 | 2745 |
If we compare these ballistic limits to the historical data shown in this document here:
When we compare the two sources, we see that the uncapped 2pdr AP has less penetration, and the 2pdr APCBC has more than shown here.
Since the 2pdr AP tested is explicitly indicated to have been tested against an average 260 BHN plate, the 2pdr AP data in the candian table must’ve been normalized to even lower hardness, probably 237/240BHN.
While the 2pdr APCBC data is probably against production armor plate that in this range (up to about 80mm) has hardness generally higher than 260 BHN. Which is why its penetration is lower.
Any way to determine whether large caps are going to function the same way?
I feel like the larger the caliber, the larger the difference in BL for capped and uncapped AP.
What makes you think that? Have you seen any data that suggest this to be the case?
Theoretically, I don’t see any plausible physical mechanism that could make this happen.
No, just a feeling.
Something like the: As the diamter increases the weight of the cap increases exponantially, or something like that.
Well so does the rest of the round, isn’t it?
It all gets increased at roughly the same rate, all by the same percentage, wouldn’t it?
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Probably. But I think that AP shells might get too heavy, when you upscale them.
I think bigger shells are generally shorter than small shells.