So I did just that (2.75), the md3 exporter worked fine, as well as Preach's tool, but when I open it up in QME, the model's all yellow and it has a shitload of nameless frames (even though the second time I tried that I made sure to put the timeline cursor at the very beginning).
I've seen in the InsideQC forums you have to make texture assignment, but I have NO IDEA how to do so. The post itself didn't help (and the noob-smashing tone definitively didn't help...), and even the Blender wiki itself doesn't tell you where the texture pannel is, or where the mapping tab is... https://www.blender.org/manual/render/blender_render/textures/mapping/uv/applying_image.html

It's so frustrating ;-; 

not very experienced with this, but try to isolate which step is going wrong. Maybe use noesis or another md3 viewer to confirm the md3 export went 100% correct, then go from there.. http://richwhitehouse.com/index.php?content=inc_projects.php#prjmp91 

My md3 converter tool doesn't know anything about the texture you applied in blender, it sounds like you've just got the default texture. One thing to try initially is using QMe to import your skin "by hand". Go to the model properties screen, and rescale the skin to match the dimensions of your texture. Then import it and check it looks correct.

If that looks right, we just need to adjust your text file that md3tomdl is using. Your file must be an 8 bit pcx file in the quake palette, and you need to specify it with a line

skinfile filename.pcx

If it's still wrong in QME, then I expect the UVs are getting corrupted somewhere. I'd go with ericw's suggestion of checking the MD3 with noesis. Then we know which step has failed. Don't give up, this bit is really frustrating the first time - but once you've made it work it ought to be much smoother next time. 

I am using some static entities in my map that I scaled up very large, about 512x512 units.
Problem is that they have a skin file that is 312x156, maximum qmle has.
So in game they look rather coarsened.

Is there a way to use a high resolution in the same way the normal textures are upsized? 

Downloaded Noesis and the md3's texture is all white. It says there's a material but no texture.
This is literally the only thing that I can't fix, because everyone is just so fucking vague about proper texture assignment on Blender!

Also I fixed the "export with 250 frames" problem, and it was just a matter of going to the timeline and putting "start : 1" and "end : 1". 

Can you upload the MDL file, and maybe the MD3 file as well, somewhere so I can take a look? It might be that it's working well enough to make a valid MDL even if the paths on the MD3 are wrong. 

http://www.mediafire.com/download/l6ij34q3576s8v5/infantry_gun_-_nailbuster.zip

The zip file also includes the 2.75 blender file if you're curious, as well as 2 directories, the one being the first try, and the second one where somehow the md3 exporter produced a file 100 times smaller than the first time, but the result was still the same. 

The material in Blender is irrelevant to what is put on the model.

Also, preach 's tool does not name frames, but they aren't that important anyway, it's just annoying when previewing.

Make sure not to save in qme as you will loose some vertex resolution. 

The material in Blender can be completely divorced from the material you end up applying, but it turns out that the MD3 exporter wants you to set up your material in a very particular way:

1) Go into edit mode on your mesh, and on the properties section click the button with a sphere (Materials)

2) Click the + button near the top to create a new material, then click the assign button to apply it to your mesh.

3) Still in properties, click the checkerboard button next to the sphere (Textures), and scroll the control back up to the top.

4) Click the + New button to add a new texture to your material.

5) Scroll down to Image, and click the picture image. A list of images appears, pick your g_infg.bmp image from the list.

6) Scroll even further down to Mapping, and click the button right of "Map:", then select your mesh to import its UV map.

Then export the MD3 and it should work correctly. I hope... 

http://image.noelshack.com/fichiers/2015/39/1443347869-infantry-gun-done.png

Now thing is, at the start the texture came messy, and in Photoshop, the way I saved the texture is as follow: I saved it as an 8-bit bmp image and then saved is as .pcx, and there was no option. I had to import the pcx file for it to show properly.
Also, the front side of the cylinder's texture is off by 2/3 pixels and some texture edges (that looks like the UV) seems like they're a little bit torn if I look closer.
Is it QME or should I worry about this, likewise for the texture that could be as messy IG(because I've been told to not save under QME or I'll have vertex problems)? 

If you have to Ave in qme, it's not the end of the world, but when you go direct from preach's converter, you get better vertex fodelity 

Here's a possible explanation of some of the UV distortions. Quake uses integer UV coordinates, so the UVs are effective snapped to the centre of the pixel. This is a feature of the format, not QME, so the only real solution is to design your UV map around that. I end up zooming to pixel level on the skin in my model editor and moving the UVs to the centre of the pixels when I'm trying to get sharp edges exactly right. Of course, this knowledge is not near as helpful after the fact! 

The original software versions of Quake (as well as some source ports) assume UV coordinates to be between pixels. GLQuake and derivatives move them to the pixel centers. I wouldn't recommend making any pixel-perfect detailing - it will always look like crap in some engines.

Blender plugin adds another problem: it places UVs between pixels when importing models, but (apparently) tries to align them to the pixel centers when exporting. If you snap your UVs to the pixel corners, small distortions are inevitable because of round-off errors or something. 

It's not really about distortion, but more about how some edges leave a very thin transparency line, no matter how much I try taking UV points to pixel centers. Is it related to how even models have to respect a grid too? Because I don't think Blender can do that.

If it is nothing, I can finally do the viewmodel! Speaking of which, I've been thinking of something: Instead of doing the usual fire mesh when the weapon fires, I thought about doing a Q3-like muzzleflash effect but with Powerslave's M60's muzzleflash ( http://www.spriters-resource.com/pc_computer/exhumedpowerslave/sheet/30756/ ). Will it work if I make a flat mesh with said muzzleflash surrounded by the transparency color? 

So I just did the viewmodel of the Infantry Gun/Nailbuster, complete with animations, 17 in total: without counting the standstill frame, it has 1 rise-up frame with the muzzleflash appearing, the next frame has the weapon getting down a little bit, only for the next frame to kick it again with another muzzleflash appearence, and the animation goes 0-1-2-3-2-1-2-3...
It looks great in Blender, I export it as a md3 file. I open it up in Neosis and the frames play flawlessly. Now I use Preach's tool, and that's when things get wierd.
I open QME to see if things went right, but when I choose every frame except 0 and 2s QME says "Access violation at adress 00499BDF in module "qme.exe". Read of address 0000004C.", the frame doesn't show up (but frames 0 and all the 2s show up just fine) and the mouse is spazzing out until I click. What's the problem here, and how do I fix it?

Also, this is still on subject but not for this issue, for color #255 to be properly transparent, you have to add { before the texture's name, right? Because QME doesn't seem to register that, and the pruple color is still shown. And sais former problem happens even without that { thing. 

I don't think masked/transparent textures work with .mdl files. 

Fifth is right, you can't do transparent on a mdl in standard Quake. Usually when I get an access violation in QME it's because some of the UVs have moved outside the skin limits. QME hates that, non-software engines actually cope OK with it. So that's one theory.

On the other hand, the earlier version didn't have an issue with this, so unless you had a reason to tweak the UVs it's probably not the cause. Perhaps I might need you to upload the latest file and I can take a look again. 

http://image.noelshack.com/fichiers/2015/40/1443735496-spasm0000.png
http://image.noelshack.com/fichiers/2015/40/1443735494-spasm0001.png
http://image.noelshack.com/fichiers/2015/40/1443735496-spasm0004.png 

I am envious. I would love to make a model for Quake 

good job on following that through to the end. the hardest stuff is always the first mod/model/map/whatever.

also, i really like that 'hand crafted' muzzle flash. very nice. 

Good stuff, glad all the work's paid off. I may have to write up the stuff above about how to get blender to spit out an MD3 file on my blog - it's certainly far from intuitive... 

that muzzleflash is 100% Wolf3D.

i can just hear it guten-tag'ing rooms full of dudes to death 

I am having no luck installing QME on my Windows 8.1 machine. I don't really have much desire to have these crappy old abandonware tools from the 90s on there either tbh.

I don't want to edit anything, just view .mdls and animations.

Has anyone suggested the idea of introducing a simple .mdl viewer into something like QuakeSpasm? 

A simple model viewer QC mod would suffice. I assume one is already out there - anyone know? 

Create a map with an entity class of viewthing. Then use the commands

viewmodel
viewframe
viewprev
viewnext

to play around with the model and the frames. Need a mod to set the skin I guess...