tl;drAnyone know a place to get engineering diagrams for different bullets?I've had a ballistics project in mind for a while and I have some spare time and motivation to look at it at the moment.The idea is basically to do some proper analysis of various bullets and bullet designs using CFD to produce some higher quality information about external and terminal ballistics behaviors. For example, the depth where tumbling begins for a given round should be determinable as a function of shot location, velocity, spin rate and AOA. There are similar things for fragmentation, overspin etc.The sticking point is that finding reliable figures for the shapes, construction and composition of various relevant bullets is difficult or impossible. I'm not clear on any solution other than buying samples of all the different bullets, measuring them and then destroying them with a bandsaw and trying to reverse engineer the internal construction and materials - that's a very slow and error-prone process, sort of a non-starter.Even finding engineering diagrams for something like M193 is difficult, and the ones you can find are very low quality (see picrel). They're of such poor quality that the legends are not reliably readable and I need to extract/verify the shape from the diagram.If you're curious M193's shape, in calibers is:3.3764 long.From the base forwards:The boat tail is at 9 degrees with a length of 0.4454.The bearing surface is 0.7572 long, containing a cannelure in my example of 0.1896 length and 0.3528 depth with a 20 degree throat on either side, but the specification notes that the cannelure can be whatever manufacturers want.A tangent ogive of 5.479 radius.Interestingly, the meplat has a listed max dia of 0.2227, but does not appear to be flat in the diagram: Instead it is round with a radius of 0.1896 (and the extra length it takes up is subtracted from the ogive).
Picrel is an example of the sort of thing I'm talking about, in this case flow velocity around an airgun slug shot at low velocity into water.
>>64927248Err, picrel.
Ballistic Performance of Rifle Bullets by Bryan Litz. At least I think that's the title. One of his many books is basically just a bigass list of tables of detailed ballistic data on various bullets.
>>64927144Saami has those for casings but no thing for bullet.You said reverse engineeeing so go measure and dial in a few bought bullets. Tool & die maker for all the bullet swaging most likely won't pass those out.CFD is not easy and license isn't cheap. This is master to phd level of learning calculus. And the result after hours of gpu crunching is as good as the assumption made in the first place.>>64927255You can see how rough the mesh is one bullet length behind the bullet. Anything less than that you are better off designing, making the die and shoot it yourself with radar. God in the loop simulation...
>>64927813openFoam is free and has been sufficiently capable so far, and none of it has been particularly difficult thus far since none of the initial things I'm looking at are very theoretically challenging. I haven't yet gotten to looking at deformation and fragmentation, which is where I think I'm going to hit my first real roadblocks, but so far it's been fairly smooth sailing, even up to exploring yaw depth from shifting CoP and loss of gyroscopic stability at different AOAs and spin rates.The meshes are very rough on that because the inputs are rough and it's run with pretty relaxed conditions to make it quick while I'm iterating with processes. What I actually want to do, and the reason for this thread, is find some good sources for engineering schematics and then algorithmically translate them to a 2d signed distance function that I can then revolve into a 3d shape and generate arbitrarily detailed 3d models from. (There is another way of doing this using an LLM to go to a parametric intermediate description that works for more general mechanical diagrams, but in my experimentation it's been wildly inefficient compared to the first and isn't necessary for things as simple as bullets).Assuming such a source exists and everything in the pipeline is working well enough, I can just leave it running on a farm and to crawl across the simulations for all the different bullets. The empirical route, for eg with radar for external ballistics, is unappealing because it scales so poorly since a lot of the testing is slow and cumbersome to do (eg testing yaw depth in gelatin blocks is a huge practical pain for anything more than a couple of serials). What I would much rather do is leave some compute running for a while to generate a bunch of testable predictions and then use them to validate the simulations experimentally.If I can't get a good source, then I'll probably pick a couple of rounds with well known dimensions, and then interpolate between them.
>>64927481Sadly I think this just has BCs and stuff. One of the problems that doing what I'm talking about would solve is the cases where BCs don't work well because for eg the shape of a round isn't enough like a reference BC or it varies across what you're doing, for eg an overspun bullet presenting different area over its flight path.
>>64928036https://forum.cartridgecollectors.org/t/siamese-8mm-ammunition/7671/13Looks like these autists have drawings>>64927144Why are you doing drawing in geogebra. Shouldn't you be using CAD tools and type in the values given in the dimensions? Then you can do the revolution surface in cad and generat
>>64928300Most of the dimensions are not fully legible or missing entirely on the blueprint I had because of the bad quality. I was using geogebra to find the missing dimensions, or range of possible values for the missing dimensions.Nice spot though.
>>64929157Maybe you could have erode or skeletonized erode the overly dark bw image.https://archive.org/details/5.56x45mmBullet55grainFMJSchematic
>>64929314That's a nice find.
