By 'gritty' I assume you mean 'grainy'. In other words, an image in which you can see the grains or particles of silver which make up the image on the negative.*
There are several things you can do to make the final print image grainier. The first is to begin with a fast [high iso number] film. Kodak's Tri-X [ISO 400] comes to mind here. There may be others even faster.
Next, if you are willing to pursue this further, think in terms of big enlargements. The more you enlarge an image, the more you enlarge the grain and the more it will show in the final print. You can compose a picture so that only the center area will form the final picture, enlarge it and then, when mounting, matte so that only the central area remains. Unfortunately, if you're using commercial enlarging services, this can be something of a budget-buster. If you do your own enlarging, it's not a problem.
If you wish to go further, you might consider developing your own film [Ed. There's a series of articles on b&w here on TPF. One of them deals with film developing.] By chosing a very energetic developer, you can increase the tendency of silver grains to 'clump', for lack of better word, during development.
As an aside, do look at some of the pinhole camera pictures posted on this site. Are these images similar to what you're looking for? If so, pinhole photography's an interesting thing to fuss about with.
*Of course, if by 'gritty' you mean the harshly lit, contrasty pictures linked in your IP, that's another matter entirely. That effect is due to lighting and the choice of high contrast while making the print.