Reloading mistakes ??? I've made em' all. What do you want to know ?? LOL
Actually, I've never supercharged a cartridge before. I loaded about 300 44 mags up, only to find out my wonderful Lee Pro1000 (now gone thank God) wasn't throwing a charge every 3rd or 4th round. Wore out a dowel knocking squibs out, and had to resort to my cleaning rod. Eventually, I gave up and took the rest home. Pulled about 200 with a bullet puller.
I loaded up about 200 30-30 with no gas checks. I had just started bullet casting and didn't read enough. Bullets were going all over the place, leaving a grey vapour trail in the air (poor boy tracers

) and leaded the crap out of my barrel.
I can't say I've ever mixed up powders, and I've got quite and assortment. I don't use too many different ones on a regular basis, so I can visually distinguish one form the other...7828 is extruded, Unique is a flake...etc.
I've crushed more primers than I can count....had them go in backwards more than a few times too.
Wasn't thinking once when an oversized, improperly cast 44 mag bullet wouldn't go through my sizing die. I leaned on the press arm a little too hard (being an idiot with mechanics hands and forearms) and broke the toggle block on my Rockchucker....yes....I managed to break a Rockchucker

........and the list goes on.
As far as using large rifle and magnum rifle primers....I do it all the time. I've never noticed a difference in accuracy, even using the exact same charge and bullet.