Nitrocellulose is a celluloid plastic that is combined occasionally with nitroglycerin and other elements such as graphite to produce powder. All powder uses it. The mfg process is technical, and often hazardous, but not overly complicated.
Now...
Think about how much nitrocellulose is used in just one 155mm arty shell.
Russia is making over 2000 a day and burning most if not all of those in combat per day.
The US is making just over 1000 per day and we can't make enough to keep up with Ukraine's demand.
We are just talking 155mm arty shells here, not any other munition.
Lapua is sending ammo to the Ukies.
Basically every country that we source powder from is selling to Ukraine, Israel, or both.
S&B's parent company is sending so much ammo to Ukraine they can't make enough and are having to find and buy externally sourced powder for the arty shells they are making
Then take into account the Israel war and how much ordnance is being expended there.
I talked to a guy at Alliant last week and he told me that they have 2 sources for Nitrocellulose. One is closing for at least a year. I asked why and he said he didn't know.
Another gentleman in the industry told me that he is seeing the ammo companies start to burn through their powder reserves and they generally are expecting to have no reserve left by the beginning of fall. Ammo prices will go up noticeably before Thanksgiving at the latest.
I'm telling you all right now, and mark my words, powder is going to be next year's version of what primers were last year.
Don't panic buy, but if you want to have something and it's available, buy it as you are able.