I stand by my previous post. In over 50 years of reloading, I've never had primers "back" out on me.
How do you know this?
How have you measured it?
Do you think your primers & pockets are exactly the same as everyone else's?
You do realize that Aldon is not talking about 'backing out' to a point of falling out, or misfire, Right? He's talking about creeping over time to ANY point different than originally seated.
I suspect this occurs with any brass still 'alive'. It's fresh springback lessening with time. Neck tension does this as well, and so do headspace settings. It comes right back with a new sizing cycle. So where the hell did it go? I don't know..
It's subtle, and shooters so into precision to notice often do not, because they load what they shoot -just beforehand.
It's my contention that this is a good idea. If I were a competitor, I could not pull OLD ammo out of a safe and head to line with any confidence, no matter how standardized my processes. I would want to see every aspect of this combination working exactly as needed, and precisely duplicated, with validation of a sample of this duplication, just before needed use... If that makes sense..
But I'm a woodchuck hunter, and can afford to lay back alittle. I have way more time to prepare and validate that I am prepared. So months in advance, I seat primers with an extra 1thou crush, partial size necks an extra 50thou in length, and bump shoulders an extra 1thou, all based on logged settings. This ammo will NOT be used for 2months atleast. Then, a week before hunting, I validate my shooting system with samples of this ammo. It should be perfect.
I cannot drive 650mi, and have a mangy marmot go caddyshack on me, without immediate schooling that this human is different.
Anyway, sealing the primers might work to stop creeping. I don't know with the forces in play here. It would have to be tested specifically for this.