The pixel measuring, although very likely disproving the current in game values, are not accepted by Gaijin. I can understand that considering the margin of error being very high especially on lower resolution pictures.
All the documentation that could be of use has already been reported to Gaijin and should be known to them already.
Now in many cases you cannot break tank from a side, so 270mm pen is much to low for 11.3 BR.
I think due to perspective it’s much fairer to measure the diameter by taking the middle thickness, and it’s important to take into account that the top of the round (or actually bottom rather) is curved, so the top is slightly higher than the rim. I don’t want to declare this as valid, but it can line up:
I also went ahead and quickly made a 3D cylinder overlap it to show the comparison between a 483mm (yellow) and 420mm (green) case:
It’s not perfect either but the 483mm one can fit it more or less, do keep in mind the actual round is not a perfect cylinder as it has that rounded top and the 420mm doesn’t fit. So what I think personally is that the shorter beige round is indeed a prototype round (perhaps even one that fitted the 26x270mm apfsds round) and the black round is the XM885 which is 5.2x19". I am just very convinced the 483mm case is XM885 especially since we have actual documentated numbers for it.
Even then, maybe we should ignore all rounds that have some perspective to them as there may be rounding errors. This picture shows a drawing of 105 and the 75mm rounds:
Which gives a different length… once again! Such fun. Anyways, given this length and the much more accurate length probably (if the drawing is to be trusted) a 3 inch difference to Delta 3 (XM885) would put it in the ballpark of a near exact 483mm, or 19" long casing. Which matches documentation and these black rounds (at least from my measuring).
I am therefore inclined to believe Delta 3, or XM885 probably is 19" long for the casing. Spookston’s tank ency article also worded it so that the pervious round (probably this 16" ~407mm, or 420mm(?) by your measurement) had M774 performance. Which according to your found stats seems to match perfectly. But then he goes on to say the breach was lengthened by 3 inches (which probably means indeed a 3 inch longer casing) which was to accomodate for the Delta 3 (XM885) round (so probably the 19" casing).
Then there is also Delta 6 with 430mm penetration. Idk if this may have used that 19" casing as well, maybe not. But it was tested apparently, however I’m not sure if they again lengthened the gun breach or tested it out of some test setup gun. But a 19" case would also be able to accomodate for it possibly, which would mean no extra breach modifications had to be made from the Delta 3 initiative. But idk, this is just me thinking out loud.
What do you think? Hard to find much more. I think having a good overview of all the rounds the 75mm gun had would be a good start. So we have at least that very short prototype one (probably housing the 26x270mm dart), the initial round for the XM274 (either it is that 407mm one or 420mm, or they are different) and then we have Delta 3 (XM885) and Delta 6. Unless you believe that the 420mm casing you measured is Delta 3, though it would make the documentated length and that Janes’ picture (listed as XM885) as well as possibly the round Stoner is holding an anomaly. I do not believe them to be Delta 6, unless you have other ideas.
Now that I see it again, yeah the drawing dimensions seem to line up with the HE round as well. Which is roughly 16", again 3 inch shorter than the 19" round that is what I think XM885. The 420mm might just be an error due to perspective or something else that I do not know of.
(off-topic) where I can find this program to calculate?
Any numbers you get shouldn’t be taken as gospel. Your setting a reference distance. That would be a “Known Measurement” then it uses ratios to base off that known distance. Perspective plays a large part in it, so you need good photos of anything you want measured.
The only reason I don’t measure from the middle is because usually the perspective messes up and its hard to pinpoint the middle plateau where the case would be at its longest.
They shouldn’t be ignored, but we shouldn’t take any estimated numbers from them as facts.
My problem is, the 75mm AD gun is the shorter casing, we known due to the AD gun using a sliding breech mechanism that there were concerns. So they made a new gun, XM274. XM274 would use the rotating breech mechanism and use the longer case. The lengthened case being extended by 3". We know from sources that the 75mm MCAAAC problem only mentions having lengthen the case by 3 inches once, which was from switch to the XM274 from AD.
IF the 75mm AD gun original case was 400mm, then I can totally agree with XM274 cases being 483mm.
75mm AD GUN
400mm = 15.75in
XM274 Gun
15.75 + 3" = 18.75" = 482.6mm (18.75 rounded up to 19")
These measurements for the cases make total sense for XM274 ammo to be 483mm
My issues is there’s to much cloudy sources and photos and can’t prove TO ME YET that XM274 is 483mm. But I don’t disagree that the estimated numbers we have for XM885 being 483mm makes total sense.
19x435mm @ In Game Velocity and Lowest stated source velocity of 1463 m/s
19x435mm @ Often stated 5300 f/s
19x435mm @ Found 5400 f/s source velocity
19x435mm @ Highest found source velocity of 5450 f/s
We are nearly approaching that 430mm stated performance of Delta 6
Some things I thought on overnight.
Do remember that M774 dimension are 26x345. Do we know if its mentioned anywhere that XM885 is longer then M774?
After re-looking at the Aberdeen photo you posted, those sabot petals are different from the Black 75mm Case photos.
There’s a lot of conflicting info for sure and I’m trying to make sense of it all. Maybe some more insights:
So regarding the 75 Advanced Development (AD), this is what it looks like according to the stoner tapes:
Now this does not look like a sliding breach design, rather a rotating breach just like XM274 (it just looks the same). Additionally, the drawing of the 75mm gun I provided earlier is actually that of the AD, for use on the HIMAG. I have found another drawing very similar to it that denotes it’s the 75mm AD and it clearly shows a rotating breach mechanism as well.
Now idk if it being the ADMAG makes it not an AD, I think it’s just an AD configured for the HIMAG however. The gun itself is probably the same as the AD.
This with the other ADMAG drawing with the round included, makes me believe the AD used the ~16" casing. And the ~420mm measurements are simply measuring errors with the left round being the one for the AD in that CTA collection picture, measuring probably around 16" irl. This is further reinforced by the actual irl measuring of that one 75mm round (color + lines on casing match) you posted also, measuring around 400-410mm (~16") in length. I do not believe that there is a round with actual ~420mm dimensions, it’s unlikely they made so many different sizes especially since this all would require redesigning the breach as well.
The shorter 75mm round on the right in the collection picture might have been the prototype round for an earlier 75mm gun with maybe that 26x270mm dart, perhaps the one with sliding breach too. That’s just speculation. But it’s like the only round of that length I’ve seen anywhere.
Then comes XM274, which would be the AD but with the breach lengthened to 19". I tried getting a picture of the round Stoner is holding with a bit less of a perspective and got this:
It’s likely that all rounds for the XM274 are black like for the 90mm, I have not seen any ones that have the black casing and be that ~16" length.
Another reason why I think the XM274 is 19" over the AD’s 16" (which is as shown before rotating breach as well) is the following quote:
Here it clearly says that the rotating chamber (breach) is what got lengthed, not a sliding one. Which seems to match the findings here that the AD shown above has a rotating breach and ~16" ammo casings (probably). Then again there might have been more AD’s during development.
But even without all this, that 19" round just exists, no question about it imo. Pixel measurements can be off but not by this much right? The fact Stoner pulls it out when talking about the XM274 breach that is in front makes me think that is correct. It’s otherwise hard to imagine where this number else is pulled from together with its association with XM274 in documents.
Now… I wonder if there is a way to contact ARES inc, probably not anymore?
iirc It was said on the old forum by someone or Spook that the 75mm AD was sliding or a earlier version of it was. There was a sliding breech 75mm at some point early on in the program.
I know for fact there is no 420mm case. 400mm is one of the 75mm case length. the 420mm come from estimations. Don’t fret of trying to find a shell casing thats 420mm.
100% Agree that there are two case lengths. 400mm and 483mm, no questions asked.
The confusion comes from trying to estimate case sizes in photos and the photos we have with those estimated lengths don’t entirely match up(To me). Of course pixel measurements can get close but shouldn’t be used to prove anything. They should only help reinforce evidence. Until either more information gets found or released I don’t think we will ever get a solid confirmation on XM885.
I couldn’t say. I would definitely want to visit Aberdeen to see if they still have that 105vs75mm APFSDS display.
Got bored so I modeled it and converted the volume into weight from the weight of tungsten.
The scaling of this photo was too thick, after scaling the x dimension to 140 these were the results
425mm Length x 20mm width with a weight of 2.34KG Gaijin probably got the weight right
The scaling of this photo was too thick, after scaling the x dimension to 140 these were the results
As far as im aware this cutaway picture isnt a 75mm shell. Nevertheless good modeling and technical work.
Edit: I had this picture saved as there is a cutaway of a XM885 casing used for XM274 Erosion testing document which we can see.
And there is a declassified document stating that XM885 has a Length/Width ratio of 12:1.
I also see your using Gaijin’s velocity, you could also show the other velocities that XM885 has been documented to be shot at such as 1615m/s, 1645m/s and 1661m/s.
So, in game core diam, now 26mm. 26*12 = 312? Or it must be ~diam 22mm and length 264mm?
IS Current dimension 270x26mm? Assuming you keep Gaijin’s current fantasy dimension but adhere to the declassified doc then in game the dimension should be.
270x22.5mm or 264x22mm but we also know that XM885 is longer then 270mm anyways so regardless, dimensions are wrong as is the penetration and velocity and arguably RoF too.
Edit: After having to find that source again and re-reading it, I currently don’t know if the current in-game XM885 is considered the 2-pound or 3-pound penetrator as in the documents itself, its says the 3-pound penetrator has a Length/Diameter of 12:1 and not the 2-pound penetrator.
Ontop of the weight the document uses pounds for XM885 weight but as we know 1 pound = 0.45 kilograms and XM885 currently has 2.27 kg mass so Im not sure if they meant 2 kilogram and 3 Kilogram projectile or what.
Im trying to figure out why gaijin didn’t give it an ammo box, it already gets screwed at 11.7 while 2S38 sits at 10.3 but it only gets 26 rounds.
As I have said I think earlier as well, I don’t believe this is about XM885. It’s too early for it to probably exist.
This is a snippet from the fiscal year 1984 document, itself from 1983, here it clearly says XM-274 was only a very recent development and only test fired in February that same year. And afaik XM-274 is the only gun capable of firing XM-885, which required the lengthened chamber to 16" (which matches the casing dimensions of XM-885). The unclassified document is however from all the way back to 1975, I feel it was likely some precursor development. Weight of course, as you mentioned, doesn’t add up either. There’s a document with the 16" casing (XM-885 presumably, also currently used source by Gaijin) which has the ~2.3kg projectile weight, which is more like 4.5lb.
And of course then we have the picture of the XM-885 on stand. Quite clearly can be seen that the L/D of XM-885 far exceeds 12:1. It may have been a mockup, or heavily jacketed, but I doubt it. Anyway from there from tip to beginning of the fin (which is definitely penetrator) it has a L/D ratio of more around 17:1, whereas if you take the entire length it’s around 22:1, these values are more fitting for a long rod type projectile.
Appreciate it! I was under the assumption it was the correct cartridge.
Upon reading that document of 2 lb vs 3 lb penetrator, I can only assume that’s Delta 3 vs Delta 6. I believe that is just the tip of the sabot
For clarity what they mean by Nato single heavy
So delta 3 can penetrate all of those targets except for the triple heavy.
Since we know that the tests of 2000m were done and defeated 152.4mm of armor at 60 degrees we can safely say that Delta 3 should be at 152.4mm instead of 135mm but we don’t know past that.
As @CalvinAz said, the declassified document talking about Velocity and L/D is off based on other documents talking about which year something was happening.
Given the few pictures we have of XM885 clearly show it can’t have a L/D of 12:1.
There’s just not enough clarity between the few pictures and few documents we have to get an accurate representation of XM885. And thats more than likely the reason why Gaijin has left XM885 the way it is.
The only thing we know for sure is that XM885 has nearly M774 penetration levels but the ~6 documents which collaborate that claim isn’t enough for Gaijin without accurate dimensions of the physical projectile.
Wait I just re-read everything and we overlooked something
Penetrator as in the DU tip, not the whole sabot
I’ve changed my thought process a few times but I think it’s like this. For example if the diameter is 20mm, the penetrator is 240mm
Yes? Every 12mm in length is 1mm in diameter.
But the 12:1 doesn’t match with the pictures of XM885 we have.
This is apparently one of the main sources for XM885 that Gaijin used:
That 75mm APFSDS looks more short and fatter which aligns with the 12:1 but the other picture of XM885, clearly shows that its more narrow and longer.
