I need some sort of cutter that will open up the diameter of large primer pockets. I have trimmers for depth but find nothing that will cut the sides.
I’ve switched primers for brands that had slightly smaller diameters but can’t even fit those now.
The problem is with low pressure cast bullet loads in straight wall cases. Even though I anneal the neck, my assumption is there’s enough blow by to exert pressure around the outside of the cases to tighten up the pockets.
Guess I could try a high pressure load every once in a while to loosen them up but I’m not up to very many high pressure rounds in a 45-70
If there is not enough pressure to expand a neck that is .015” thick and seal the chamber, there won’t be enough pressure to collapse the case head that the diameter is about .200 thick around the primer pocket. Besides the case walls would collapse long before that as an indicator.
What I would look for is if the primer is protruding from the pocket after firing. This will more or less show if it’s a low, medium or high pressure.
High pressure most people are familiar seeing. Primer pushes out, case pushes back or stretches to hit the bolt or breech face, re seats the primer, case head expands, primer pocket loosens.
Medium pressure like a 30-30, primer pushes out, there’s enough pressure for the case to stick to the chamber walls, but not enough for the case to move or stretch back to the bolt or breech face, primer remains proud of the case head when removed.
Low pressure, where you may be. Primer pushes out, not enough pressure for the case to grab the chamber, case is forced back against the bolt or breech face and re seats the primer. Here’s where it gets tricky.
The casehead on a low pressure load can actually hit the bolt or breech face harder than a high pressure load. The high pressure load is tempered by stretching the case. The medium pressure load doesn’t hit at all, the low pressure hits full force. The high pressure load will also stretch the casehead and loosen the pockets.
What seems to happen with low pressure loads is that the case head hits the bolt or breech face and peens the primer pocket. It doesn’t close, but more or less forms a crimp like a military round. A couple twists of a chamfering tool will generally remove the peened over portion. You might be able to feel an edge at the top of the primer pocket with a bent paper clip or pin.
Or it could just be carbon built up in the pocket and it needs a good brushing.
Low pressure loads create all sorts of new issues to contend with.
