This morning, those STS primers were tried in a different rifle, the Optima V2. The load was the same as in the OP; 200g Shockwave, and 115g Blackhorn. The sabot needed changing to Harvester dark blue, because the Optima is a 50 caliber. Note, there is zero leakage through the primer!
Then the notion came to try a heavier bullet, and see what happened. There were some 300g XTP rolling around in the truck, so they went into the rifle. The primer stuck in the breech plug. The load was 115g Blackhorn, 300g XTP, Harvester short black sabot, and the STS primer. All three times, the primer stuck tight in the breech plug, and required a leatherman. The primers show the marks on the rim, which were made by the leatherman tool. Even using the tool, removing the primers took a bit of effort. Note, the primers didn't leak.
The previous 6 shots were all made with an o-ring in the primer socket of the breech plug. The next 3 shots were done after removing the o-ring from the primer socket. There were no more XTP, so 300g Deep Curl from last hunting season were used instead. The load was 115g Blackhorn, 300g Deep Curl, Harvester short black sabot, and STS primer. These primers could be pulled some out of the breech plug, but fingernails were already busted up from the previous primers, and the leatherman was handy, so the primers were easily pulled with the tool. Note these STS primers didn't leak.
