3F can be used for pan powder and some say they see no difference in ignition times, I myself use 4F in my pan. As the fellow above said ,if the company you by powder will not mix cases then its time for a new company . I have not found powders harder to get just harder to get locally. The little guys cant compete with internet sales , at the same time meet the federal reg and keep the cost down . For every case I purchase I order at least 1 lb of 4F. 4F goes a long , long ways and one can should last about that long or longer .
As to rolling your own . Yes you can . Is it safe ? Well that depends on how you do it . We used 2 or 3 round balls in a small wood container. Put about 30 grains in at a time and shake it .
Another way ,If you watch you will see small wooden black powder pedestal sets sold now and then on places like e-bay . The trick is to not get in a hurry , be safe about it and keep any and all ignition sources completely clear as you work as well as keeping the amount of powder your working on small this way if something does happen your less likely to have a serious injury.
Now how well does this work ,,, well not to bad except for a couple things .
1) your grain size is not consistent. You will have powder from 9F down to the grain you started with . BP is sized and made through a screening process to assure the best consistence possible .
2) the powder you have just re sized is broken and thus does not have a completely glazed surface . What this causes is the powder to be more acceptable to moister and if the humidity is real high you can find that you pan will turn to muck in considerable more time then what manufactured 3 or 4F in your pan will
Well there you go some things to think about . My only sure advice would be to make sure if you decide to grind your own that you dont do it in anything that could create a static spark . Many now believed that static electricity can not set of BP even at finer photo grades like 7 -9 F. I myself am not sure I subscribe to that line of thought but
? But it cant hurt to play it on the safe side right ?