Well, You have had some good (and some ho-hum) suggestions but to my way of thinking, none of them is optimal.
Nothing beats shooting the stuff. Just take them out and fire them at the ground if nothing else. If you do not have a firearm of this caliber and can't get one, give the cartridges away to someone who does have. This method disposes of the entire cartridge's explosive ability including the primer.
Remember, if you pull the bullets and dump the powder, you still have the primer. Do not try to knock/punch it out with a nail or something!! Outside of the firearm, the primer will become a projectile itself!!
IMHO the best way is to fire them.
Second best way is to give them to some one who will fire them.
Third way is to pull the bullets (if you know how and have equiptment), dump the powder (anywhere-yard, garbage can, anywhere) and then fire the primer. This is a distant third. Mostly because you are asking tells me that you do not know and understand how to safely do this..................If you did you would not have to ask.............no disrespect intended.
To a large degree, the answer depends on how many we are talking about. I would not put a lot of unfired powder into the garbage can...........it might get ignited somehow. You might also give some thought to the powder falling into the wrong hands like kids or novices..............I like strewing it in tne yard. If there are a lot (greater than 100 rounds then give them away (somebody will want them)).
I do hope this helps.
PigPen