Time better spent doing this. Some people would be surprised to know that variations in neck tension cause fluctuations in release pressures that affect velocity and accuracy.
After seeing many others who say they don't clean primer pockets, I guess I'm not embarrassed to say that I rarely do it. When I inspect a decapped case, if I see an unusual amount of carbon in a pocket, I'll swirl a machinist's scribe around in there and break it up. I don't do it as a routine.
Hand loads should always be checked for high primers. That's one reason I always box mine bullet point down, one last QC check. Re. the busted M1 Rifle, it should be able to endure a slam fire using M2 Ball pressure level ammo; the sheared heel is more likely a result of a hot or over-charge. Or simple metal fatigue.
Personally I agree with not dinking around with primer pockets in pursuit of uniforming. We manage to get enough loose ones without trying. But then again, I'm kind of a "service grade" shooter who wouldn't appreciate a difference of a millimeter or two on paper.
