Re: excessive primer pocket depth?
A while back I was handed an opportunity to see that primer striking is way bigger than talked about.
My son's Cooper started throwing big fliers. This was a solid 3/8moa gun that seemed to drift off into 3/4moa. And it was a gradual, but abstract change.
I chased my tail on it for over a month, swapping scopes, checking bedding & action screw torques, checking max OgvOAL. I changed bags, tried different barrel cleaning & fouling. I disassembled the bolt a couple times and found no issue, and went into the trigger, no problem.
The gun just stopped shooting well, as it was triple grouping. That is, if I fired 10 or 20 shots at a single bull, I would end up with 3 relatively normal groups separated from each other, and they didn't walk there in order but randomly landed into one area or another & back.
Also, ES was higher than I'd ever seen from the load, and I knew there was no aspect of my ammo that had any issue. This put primer issue in the back of my mind(bad lot?) Couldn't prove it..
One day I got lucky as hell; a misfire. About 30 shots later, another misfire.
Back at the bench I measured the fired firing pin protrusion, cycle, dry-fire, remeasure(bunch of times). Found that my pin was intermittently slipping through it's set-screw in the cocking piece, resulting in several protrusion distances.
I had pulled on the pin earlier while checking the bolt, but my scrawny little pull check didn't get it..
Start over, where should the pin be set?
Back to the range with a bunch of tools and my standard load. Tweak the pin setting 5thou protrusion at a time & firing groups. Took a while to home in on it, but I ended up with one setting that was better than all others -with that primer -and my standard seating(3thou crush in uniformed pockets).
With this info I went back to the bench and dimpled the pin to put it on the magic setting, and double set-screwed it -with locktite!
Now my kid's Cooper shoots solid 1/4moa and no more mystery fliers.
If I had never seen the gun shoot better,, if it had come to me shooting with this problem,, I never would have had any luck with the gun. I would have assumed it needed a better barrel. Then when that didn't work, I would have separated the gun into several dumpsters and been done with it.
Now I have a lot of things to test and learn about primers & striking of them. I should be out there doing it today!