We’re you using a different batch of powder ?or a fresh powder or powder from a keg you have used for your work up sounds like you have covered everything else im also a seasoned reloader good luck I will be monitoring this thread you have gotten my attention now I’m curious have a safe day
I # 1 decapp # 2 sonic clean using Lyman brass cleaner for 30 minutes # 3 dry with heat gun #4 anneal # 5 into tumbler using corn cob media for 3 -4 hours # 5 wipe down with clean cloth and inspect in that order the brass comes out looking new and I hope this helps looks like you are covering...
No by all means keep the STW I hunt with one myself I also reload so I’m no stranger to shortages of EVERYTHING! as to what caliber for your son you might consider a custom muzzle brake for the RUM you would be surprised at what you can find for reasonable money but please make him his own RUM...
This is a clamp on i recently put on my 7 mag works great no vibration issues at all about 70% reduction in recoil I have fusions in my back and neck so recoil reduction is a must for me again good luck
Witt machine also has custom clamp on brakes made to order for any barrel size they guarantee at least a 60% reduction in recoil you can Olson check out trident https://jcb-solutions.com/products/trident223 these guys made the brake on my 7mm STW reduced the recoil to a 6.5 creedmoors recoil...
You might want to check the shellholder different manufacturers have different specs for shellholders I have run into that problem with a 6.5-06 or it could be a tighter chamber on the new barrel or a few other things as these guys have suggested they are pretty sharp
I have run into the same problem with multiple manufacturers I think it’s a cost cutting method from the manufacturers small bits of hundreds of thousands of rounds add up that or just **** poor quality control I have no idea which
Looks like the bullet was way to heavy back pressure had to go somewhere thank goodness nobody was by injured that’s just another reason to take up reloading