I would like to learn how to ID powder. How do you do that? If I put out a spoon full of 8 different powders here, then three will look the same - I can't tell the difference. I did pull down someone's hand loads - was several visually different powders used - might have been perfectly full of sense to original loader - but was no notes - and I did not know how to ID those powders. So I burned that powder as waste.
Similar with the primers - how to tell one from the other - I do not know how - so all "popped" and made a bang when I fired off the empty cases in the rifle - but if I used them, I would not know what kind to get for next batch (if they worked well) or what kind to NOT get (if they did not work well) - Magnum versus Large Rifle in Federal have different colour showing through flash hole - but I do not know about CCI, RWS, and other primer brands - or other Large Rifle versus Magnum primers. From outside, all look the same to me (except colour - brass versus nickel in some brands - and factory Norma have that little symbol etched on the outside primer face).
Your questions are good one and are, of course of central importance to this thread. There are lots here who more about this than I - as I have really just recycled my own reloads so far - and have seldom if ever recycled those of others. I consider myself to be very good at the mechanical aspects of taking loads apart and putting the components back together in other loads. I'm a big advocate of using collet bullet pullers where possible and almost never use a kinetic bullet puller - reserving the use of one of those to removing bullets that you can't grip with the collet (like 40 S&W) and those where the bullet would be damaged by a collet puller (i.e., the lead ones).
As for removing primers – in a non-destructive manner – I tried using one of those Lee decapping dies but – at least in my case – that left the primers to free fall into a bin, and they often lost their anvils, as a result of that turmoil. Then, I switched over to a the Frankford Arsenal platinum series hand deprimer that basically is sort of a gun that uses your squeezing power to pop out the primer horizontally, so the impact of the primer into the catch tube isn’t enough to damage the primer. It does a tidy job too – and you can watch TV while you are doing it.
I just use it for one lot of cases at a time, so at least I’m not likely to me mixing recovered, unused primers of different types. That leads me to rely on the type of case the primer came from to suggest the type of primer is involved. In other words, if I pulled the primers out of a whole bunch of 308 cases that I primed awhile back, I naturally assumed that those primers were, in fact, large rifle primers. I get it that, if you were recovering primers from somebody else’s reloads, it's possible that person used large pistol primers – or magnum large rifle primers – in a large rifle case – and all that.
For just that reason, I am careful that if I have any doubts what type of primer the thing is, I only use it in a bolt action rifle. Pistol primers in a rifle aren't going to create any problems unless it is a semi auto with a propensity for doing slam fires – if the primer cups are soft. Conversely, in the real world, I don't think it is a big deal if one unintentionally uses a large rifle primer or even a magnum large rifle primer in a pistol load as long as you are staying under max loading levels – which I always do.
There will, of course, be purists who are ripping their hair out now at the thought of me possibly using a magnum large rifle primer in a 308 case that doesn’t require one etc., but frankly, it's no big deal. People also claim that they can tell one type of beer from another, but having run a pub for a while, I know that after we ran out of Blue and started handing people Canadians – in a plastic cup – no one ever came back and said “
hey, I asked for a Blue and you gave me a Canadian.” Then again, as far as I know, OkayShooter never came to our bar when we were doing that.
Distinguishing one type of powder from another is absolutely the most complicated part. This certainly involves the use of deductive reasoning, where I suppose one would start by looking for any notes left by the previous reloader and then reality checking these.
Obviously, it's possible that the note is incorrect. I would look for circumstantial evidence as well. For example, if the guy left a note saying that he had used 26.5 grains of 1680, I would check to see if that load made sense for the cartridge involved. Then, I would examine the powder coming from a bunch of the different reloads and see if, in fact, it was the same as what the guy had indicated in his note. I’d do that by matching the appearance of the unknown powder against some other powder that I knew to be that type (say a bottle of 1680 from a store).
If the appearance test checked out, then I think one should also go ahead and do a density test. The way you would do that is to use some way of dispensing a known volume of the powder – say using one of those Lee powder dippers type powder measures. Then, weigh that volume and match it against the Lee chart that tells you the expected weight for that volume of powder. For example, a 3.1 cc dipper of AA1680 should weight 43.7 grains. If the density check seems to also suggests that the powder is – in fact – that type, then you can apply the scientific axiom of “
quod erat demonstrandum”. That principle – when translated from Latin into English – says that “
If it looks like a duck and walks like a duck and quacks like a duck, then it's a duck”
Finally, when assembling the pulled-down components into a load also respect the other Latin principle at says “
probare tua formula apparatu aliorum”
. 
