I don't usually shoot 35mm, but I do own a Minolta SLR I use from time to time. As most film photographers out there, I'm always trying to cut the cost of shooting with my cameras. One of the logical money-saving steps when shooting 35mm was to start bulk loading film.
The theory is pretty simple: instead of buying individual cartridges already loaded with a film stock, you'd buy empty ones you can load some bulk film in. You can get the bulk version of most of the stocks you can buy in individual rolls, but not all of them will make sense financially.
They usually come in a big, long roll of 100'. How many rolls you can get from that is up to you. If you were to make your own 36-exposure rolls, then you should be able to get around 20. That's if you don't expose too much film every time you load it, but a reasonable number. Some people prefer to make rolls with fewer exposures, like 16 or 20. In that case you'd be "wasting" more film (some film will definitely get exposed when loading it) but it gives you flexibility and you can still get a decent amount of rolls.
Prices vary immensily. A 100' roll of Tri-X is well beyond $100, so each roll will cost you more than $5. HP5 though, is $70, so you could get rolls for less than $4 each (you'd be saving $1 per roll). Or you could get something like Kentmere, a film stock I've used in the past and liked, for $40. That's $2 a roll! (and a $2 savings per roll)
Yes, it was going to be a bit more work but it looked completely worth it! Fast forward a few months... was it worth it though?
As I mentioned earlier, I'm not really a 35mm shooter. I'm still using my first 100' roll of HP5. I've got around 10 rolls out of it so far, so I might have another 8-9 to go. But I've already seen some flaws I want to address, since they are flaws that will keep me from doing it again.
Not really a working solution for automatic cameras
If your camera winds the film for you, this might not be the best solution. You have to make sure the motor of the camera isn't going to rip the tape you use to attach the film to the spool. If that happens (and it happens, believe me), you'll get stuck with a roll of film in your camera that you can't take out until you are in complete darkness. So no more shooting that day.
Also, you'll have to reuse old cartridges with the correct ASA code so the camera knows how to expose the film.
There's no margin for mistakes
The only way you can save money bulk loading your film is if you are efficient enough. I've made some mistakes during my first times that ruined some film. This will eat your savings.
But these little mistakes are nothing compared to THE big mistake. It hasn't happened to me, but I'm always afraid the gate of the film loader I use will be open and expose the whole role inside of it. If you waste $40 or $70 worth of film, you will have to successfully load a lot of film to make up for it.
The last shot of a roll is always ruined!
You know those -now trendy- first shots of a roll, with only half of the frame getting properly exposed? Well that happens at the end as well when loading your own film.
Because of the way you load it, when you first attach the film to the spool you are exposing that part. That will be the last shots of your roll.
And while I don't really mind losing the first shot (because I always take two, so at least one is going to be the whole frame), the last one is a completely different story. Imagine you are capturing something and it's the last shot. Not only you have lost half of what you were framing, but you can't keep shooting! You have to load another roll and the scene will probably be gone by then.
Bulk loading film is awesome if you are an avid 35mm shooter and really need to save those few extra bucks (they add up quickly if you shoot a lot). It's fun and you can make your own 16, 20, 24-exposure rolls.
But it takes work, mistakes will be expensive, it won't work for every camera and you'll lose some shots in the process.
Just this last issue will keep me from doing any more bulk loading in the future. I'll be paying a bit more per roll, but I don't shoot enough 35mm to notice the difference.