No way this primer is real!?

[FrankenMauser]

Maybe I'm lucky, but I too, have yet to seat a primer sideways. But then I have only been reloading metallic for about 30 years. Using either my RCBS hand primer or the RCBS bench primer, I look and see that the primer is orientated correctly before I attempt to seat it.

As long as you keep reloading, the clock will keep ticking.
Every primer that I've managed to seat sideways (2 or 3) was oriented correctly before the case went over top of it. I always look, as well. And, yet, they still managed to reorient themselves on the way to (or upon reaching) the primer pocket.

[44 AMP]

In my experience it has to do with the design of the feed system and the speed with which it is operated. Primers BOUNCE!!!

When things are run slowly and gently, things usually work as intended, but change the speed or force applied and things can literally go sideways.

Push the priming arm of the usual Lyman/RCBS, etc press in just a bit too hard it stops suddenly inside the slot in the ram, and while its properly positioned under the shell holder, the primer in the cup, which was correctly oriented can bounce up on its side, as this happens in the ram, and under the shellholder, its tough to see.

I had a Dillon press where if you worked the primer slide "smartly" it would malfunction, but slow, smooth, making sure you waited for the primer to drop from the tube and not letting it snap into place under the shellplate, and it worked fine. Work it "wrong" and primers would bounce onto their sides or completely upside down in the cup.

I believe the overwhelming majority of sideways and upside down primers is due to "operator error".

Even though it may seem that the primers do it on their own, they don't. It just means you haven't figured out what you did wrong. yet.

[Metal god]

I believe the overwhelming majority of sideways and upside down primers is due to "operator error".

While that may be true . I've not had a sideways or upside down primer since I switched to the RCBS hand primer . That must say there was at least some of the problem being the tool .

[44 AMP]

That must say there was at least some of the problem being the tool .

I've never had problems using the RCBS hand tool either. Its just such a different design that flipping issues don't seem it happen. Its also something that doesn't lend itself well to a slam bang style of operation.

When it is a hand operated tool, (not powered) you must always include the operator's method of using it when considering problems.

An extreme example would be a guy using a claw hammer to drive nails, but turning the head 90 degrees sideways and swinging it like an axe chopping wood. He will, eventually hit the nail and drive it in, but his method of operating the tool is ....suboptimal.

[FrankenMauser]

While that may be true . I've not had a sideways or upside down primer since I switched to the RCBS hand primer . That must say there was at least some of the problem being the tool .

All of my sideways primers - at least that I can remember - happened with an RCBS hand priming tool.
But... it was also using feed guides (the plastic clamshells) that were very worn. They were a little rough and had grit embedded in them, at that point.
RCBS sent me two new sets, and I haven't had a primer flip since. (Not caused by the guides anyway. I have had a few flip when they hit the seating stem, which required reorientation before seating.)